FULL PAPER 1 ------wileyonlinelibrary.com www.advhealthmat.de Sustained localized In many of these dis these of many In [3] [2] Skin possesses self-renewal [1] Thus, the development of epidermal [4] characteristics, characteristics, which help with the repair and regeneration of However, in injuries some and cases such deep cuts, diabetes, cuts. and infections, the self- as burns, healing capability of skin is impaired and further intervention such as growth factor delivery is required. to protect the internal tissues from patho gens and conditions. variations in environmental drug drug delivery is a promising technique to the the blood supply to the injured limited. tissue Therefore, is high doses of systemi cally administered drugs are required achieve to sufficient therapeutic effects. Such high doses may lead to adverse drug reac or side other effects toxicity including tions associated with the pharmacokinetic prop erties of the drug. orders, orders, the microvessels are damaged and prevent prevent these side effects. In addition, due to the large exposed surface area of the skin, epidermal tive drug approach delivery for administering the is drugs an that are attrac not easy to absorb orally or nasally. Department of Chemical Engineering Northeastern University Boston 02115-5000, USA Prof. A. Khademhosseini Department of Physics King Abdulaziz University Jeddah 21569, Saudi Arabia Dr. A. Tamayol, Prof. M. Akbari, Prof. N. Annabi, Prof. M. Akbari, Prof. A. Tamayol, Dr. M. R. Dokmeci, Prof. A. Khademhosseini Dr. Wyss Institute for Biologically Inspired Engineering Harvard University Boston, MA 02115, USA Sonkusale P. Mostafalu, Prof. S. Dr. Nanoscale Integrated Sensors and Circuits Laboratory (Nanolab) Engineering Department of Electrical and Computer University Tufts Medford, MA 02155, USA Prof. M. Akbari Department of Mechanical Engineering University of Victoria Victoria, BC V8W 2Y2, Canada Prof. N. Annabi 2015 GmbH WILEY-VCH & Verlag Co. KGaA, Weinheim © , 2015

Adv. Healthcare Mater. Adv. DOI: 10.1002/adhm.201500357 www.MaterialsViews.com DOI: 10.1002/adhm.201500357 Politecnico di Milano Milan 20156, Italy Massachusetts Institute of Technology MA 02139, USA Cambridge, S. Bagherifard Dr. Department of Mechanical Engineering Massachusetts Institute of Technology MA 02139, USA Cambridge, S. Bagherifard Dr. Research David H. Koch Institute for Integrative Cancer Dr. S. Bagherifard, Dr. A. Tamayol, Prof. M. Akbari, M. Comotto, Prof. M. Akbari, M. Comotto, A. Tamayol, S. Bagherifard, Dr. Dr. M. R. Dokmeci, Dr. M. Ghaderi, Prof. N. Annabi, Dr. Prof. A. Khademhosseini Harvard-MIT Division of Health Sciences and Technology Brigham and Women’s Hospital Brigham and Women’s Harvard Medical School MA 02139, USA Cambridge, E-mail: [email protected] M. Comotto, Prof. N. Annabi, Dr. M. Ghaderi, Dr. M. R. Dokmeci, M. Ghaderi, Dr. Prof. N. Annabi, Dr. M. Comotto, Prof. A. Khademhosseini Biomaterials Innovation Research Center Department of Medicine temperature temperature and forms a barrier creating a closed environment Prof. M. Akbari, A. Tamayol, S. Bagherifard, Dr. Dr. 1. Introduction Skin is the largest organ in the body. It helps regulating body topical applications. used to release two different active molecules with molecular weights similar used to release two different active molecules profiles are characterized. This to drugs and growth factors and their release smart and closed loop systems for platform is a key step towards engineering The drugs are encapsulated inside microparticles in order to control their The drugs are encapsulated inside microparticles microparticles contain- release rates. These monodisperse thermoresponsive a microfluidic device. The system is ing active molecules are fabricated using to a flexible heater with integrated electronic heater control circuitry. The heater control circuitry. to a flexible heater with integrated electronic wound area and enables controlled engineered patch conformally covers the the temperature of the hydrogel layer. drug delivery by electronically adjusting can improve the healing process during skin disorders and chronic wounds. process during skin disorders and can improve the healing engineered that utilizes thermore- achieve this goal, a dermal patch is To within a hydrogel layer attached sponsive drug microcarriers encapsulated Topical administration of drugs and growth factors in a controlled fashion administration of drugs and growth Topical Nasim Annabi, Masoumeh Ghaderi, Sameer Sonkusale, Mehmet R. Dokmeci, Sonkusale, Mehmet R. Dokmeci, Masoumeh Ghaderi, Sameer Nasim Annabi, and Ali Khademhosseini* Sara Bagherifard, Ali Tamayol, Pooria Mostafalu, Mohsen Akbari, Mattia Comotto, Akbari, Mattia Comotto, Pooria Mostafalu, Mohsen Ali Tamayol, Sara Bagherifard, Dermal Patch with Integrated Flexible Heater for on for on Heater Flexible with Integrated Patch Dermal Delivery Drug Demand FULL PAPER 2 wileyonlinelibrary.com www.advhealthmat.de n si itrae Mitr as ehne te eln rate healing wounds. and the cuts skin enhances of also Moisture interface. patch skin the at and moisture sufficient of presence the in facilitated be can factors and drugs soluble water of release the example, Formanner. sustained and localized a in drugs of release tive effec enable to needed is environment suitable a addition, In izing it with other monomers. other with it izing ( point critical its above temperatures at hydrophobic becomes and peratures tem low at hydrophilic is that material thermoresponsive a is NIPAM carriers. drug developing for researchers several of tion atten the attracted has (NIPAM) N-Isopropylacrylamide rials, peratures while the polymeric networks shrink above a critical a above shrink tem networks polymeric low the while at peratures content water high possess and behavior similar rg ares ih b a efcie prah o o demand on factors. and drugs for of release approach effective an be heating might locally carriers thus drug and applications topical for harmless be to proven been has a stimulation in Thermal carriersfashion. controllable drug the stimulating by profile release drug the tune to approach alternative an as pulses magnetic and trical, elec thermal, including stimuli different to responsive are that materials identify and synthesize sci to scientists enabled polymer has ence of field the in progress Recent desired. highly is release drug the over control active offer that systems of ment develop bacteria, resistant antibiotic of number increasing the With drugs. of profile release the over control precise allow not self-standing microparticles loaded with FITC-dextran. with loaded microparticles self-standing The d) substrate. flexible a on heater fabricated the of view Close-up c) dressing. wound integrated the of image representative A b) dressing. wound 1. Figure oml otc wt te kn uig h bd movements. body the during skin the with contact formal researchers. many of attention the attracted lately has platforms delivery drug dressings. polymeric and hydrocolloids, hydrogels, ointments, within lated encapsu are that factors and drugs releasing include delivery A topical drug delivery patch should be able to maintain con maintain to able be should patch delivery drug topical A

Fabricated wound dressing integrated with microcarriers loaded with drugs and electronics. a) Schematic showing different elements of the of elements different showing Schematic a) electronics. and drugs with loaded microcarriers Fabricatedwith integrated dressing wound [8] However, these systems are mostly passive and do and passive mostly are systems However,these ≈ 32 ° C), which can be increased by co-polymer by increased be can which C), [7] Current strategies for topical drug topical for strategies Current [9] [10] Among thermoresponsive mate thermoresponsive Among Poly (NIPAM) hydrogels show hydrogels Poly(NIPAM) © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimCo.KGaA, Verlag& WILEY-VCH GmbH 2015 [5,6] ------

is less than 37 than less is temperature surface skin the where applications epidermal for 37 above even to increased and tuned be can NIPAM of temperature ical crit The gels. the from content water the release to temperature rcs cnrl f h pth eprtr i ahee b a by achieved is temperature patch the of control Precise technique. emulsion microfluidic using NIPAM from ricated fab are particles thermoresponsive heating Monodisperse gold elements. micropatterned and sheet a in hydrogel loaded Ca-alginate are that composed microcarriers is drug patch thermoresponsive proposed of The factors. of growth delivery and on-demand drugs for elements heating flexible grated system. electrical flexible the with substrates drug-loaded of integration factors. molecules active with different molecular weights resembling drugs and growth different two using determined release are their profiles and characterized are particles fabricated the of plat wearable in and shown (schematic flexible form a create to package compact a in achieved is system the into components electronic the of tion Integra temperature. patch the in stabilize heater, and control flexible to the order to current electrical This apply microcontroller. can a system to connected is that element heating conformal contact with the skin. the with contact conformal form can that devices create to scientists enabled have tronics network. hydrogel the from fusion dif water through release drug the initiate to sufficient is heat strate using screen-printing. using strate sub flexible a on circuits electric of fabrication the by or terns pat metallic free-standing of utilization the by engineered be Here, we engineer a hydrogel-based dermal patch with inte with patch dermal hydrogel-based a engineer we Here, eet dacs n h fil o flxbe n waal elec wearable and flexible of field the in advances Recent ° C through copolymerization with other groups. Thus, groups. other with copolymerization through C ° C (an average of 31–32 of average (an C Figure [13] The latter approach enables the enables approach latter The [12]

1 These flexible systems can systems flexible These a). The physical properties properties physical The a). ° DOI: 10.1002/adhm.201500357 DOI: C), www.MaterialsViews.com Adv.Mater.Healthcare [11] a small generated small a

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) was 32 Q ≈ Figure C. The parti ° 440 to 720 µm )) were almost ≈ 0 wileyonlinelibrary.com www.advhealthmat.de d/d ∆ ( oil phase to aqueous phase × C. The dimensionless values for the percentage ° ) on the diameter of particles is illustrated as a func a). A typical time-lapse micrograph of the micro 3 Q

The turbidity and the size of the PNIPAM particles changed Figure inner tubing with the diameter of 360 µm was placed concen tric into a circular channel of 820 µm in diameter ( A solution of NIPAM (4%–10% w/v), N,N-methylene-bis-acryla mide (BIS, 0.3% w/v) as soluble photoinitiator the (PI, 0.5% w/v) crosslinking was injected agent, through the and inner water tube, while a solution v/v of Span80 was mineral flowed oil through the containing sideline inner 20% to surround tube. the As shown in were Figure monodisperse. The 2b, ratio between the the flow fabricated rates ( particles adjusted to control the particle diameter and monodispersity of the particles. Figure 2c shows that for a 10% NIPAM the w/v particle solution sizes were of changed from for the core (aqueous phase) to the sheath (oil phase) 0.01 ratio and of 0.033, respectively. form To crosslinked poly(NIPAM) particles, the droplets were exposed to UV light (4.3 W cm constant for the tested diameters showing no statistically between flow rates of the core (PNIPAM 10% w/v) and sheath stream ( tion of temperature. The results suggest a relatively sharp vari ation in the diameter of the particles as increased. the temperature Regardless was of the starts initial at diameter, 32 the shrinkage of particle diameter reduction (100 for 5 min keeping at a temperature cles around were 4 then washed to remove oil mechanism of residues. crosslinking is The shown in Figure chemical S1 (Supporting Information). when they were heated above the critical temperature ( due to transition from hydrophilic state to ( hydrophobic state particles fabricated with 10% w/v NIPAM solution is shown in Figure 3a representing the effect of temperature variation particles’ size and on In turbidity. Figure 3b, the effect of the ratio

------2015 GmbH WILEY-VCH & Verlag Co. KGaA, Weinheim © Other factors, required to [14] , 2015

Thus, we fabricated a flow-focusing device where an where device flow-focusing a fabricated we Thus, Among different fabrication techniques for hydrogel Fabrication Fabrication and characterizations of thermoresponsive microparticles. a) Schematic illustration of flow focusing microfluidic device for

[16,17] [15,16] Generating Generating a reproducible and programmable release pro Since Since the body temperature is almost constant, the use Adv. Healthcare Mater. Adv. DOI: 10.1002/adhm.201500357 www.MaterialsViews.com Figure 2. microparticle fabrication. b) Microscopic image of the collected particles. c) Size of the microparticles versus the ratio of flow rates. promotes the regeneration process. for the repair of the epidermis It layer. has been shown that in these cases providing growth factors such as vascular endothe lial growth factor (VEGF) and keratinocyte growth factor (KGF) its regeneration ability in some cases requires intervention. For example, in the case of burns and large cuts where the micro vessels are damaged, the regeneration rate of blood vessels not is sufficient to provide nutrients and factors that are required 2. Results and Discussion The restoration of normal functionality of the skin including capable of high microcarriers in the range of few throughput micrometers to several milli fabrication meters. of monodisperse drug carriers, emulsion method (droplet-based fluidic) is file can be achieved by utilization of riers. monodisperse drug car layer, layer, a heater for stimulating the microparticles, a controller, and a power source to adjust the generated heat, and a flexible cover that holds the components in place. interesting approach for controlled drug release. PNIPAM was used herein as an example to develop a thermoresponsive plat form. The key components of the platform, shown in Figure 1, include thermoresponsive microparticles, a flexible hydrogel of thermoresponsive drug carriers slightly with higher than that of the surrounding critical tissue might be an temperature that allows creating a suitable growth and regeneration environ ment for the skin while enabling controlled release of growth factors and antibacterial drugs. create a supportive environment for the healing process include sufficient moisture and oxygen supply and protection against pathogens. Here, we engineered a multicomponent platform FULL PAPER 4 wileyonlinelibrary.com www.advhealthmat.de yai rsos o te irprils ih ifrn polymer different microparticles with the of responsedynamic 43 and 29 37 around plateau a reached samples all Information) andporting abruptly 32 around turbidity was which, polymer’sheating upon shifted the the which with at interfere temperature not did critical concentration PI the changing that netgt ter eprtr sensitivity. temperature their investigate to used spectrometry absorption was temperature, UV–vis with with fabricated concentrations. NIPAM lower microparticles in pronounced more was eter diam particle in variation the Figure3d,e, in shown as The studied; was response 3c). particles’ the on (Figure concentration NIPAM groups of effect the between difference significant (*p indicator fluorometric Blue Presto using measured was viability cell media; the in microparticles obtained using The different metabolic NIPAM activity concentrations. of f) keratinocytes cultured with different NIPAM concentrations 40 to 25 from varied was temperature the as concentrations NIPAM different with diameter microparticles’ the of to 40 microparticles at different temperatures. b) Variations in the microparticles’ diameter with different initial size as the temperature was varied from 25 3. Figure ic te rnprny f NPM irprils changed microparticles PNIPAM of transparency the Since ° ; oee te xet f h triiy leain between alteration turbidity the of extent the however C; ° C (10% NIPAM). c) Diameter shrinkage ratio for microparticles obtained using different microfluidic flow rate ratios (10%

Physical and biological characterization of PNIPAM microparticles. a) Snapshots of shrinking of the thermoresponsive PNIPAM thermoresponsive the of shrinking of Snapshots a) microparticles. PNIPAM of characterization biological and Physical ° icesd y eraig I ocnrto. The concentration. PI decreasing by increased C [18] The results indicatedresultsThe © ° C (Figure S2, Sup S2, (Figure C 2015 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimCo.KGaA, Verlag& WILEY-VCH GmbH 2015 - - el, hc cnrs h ctcmaiiiy f h fabricated the applications. of topical for microparticles PNIPAM cytocompatibility the confirms which cells, control and treated of activities dif metabolic the significant between a ference not was there that demonstrate 3f Figure in results assay.The Blue assessed Presto by activity then metabolic cellular and the cells with samples parti the PNIPAM incubated We of cles. and concentrations different keratinocytes to human them exposed cultured we Thus, compatibility. bio their confirm to is delivery drug topical in microparticles slower.be to found was process down cool their during samples delayed critical temperature upon heating; the expansion of all the slightly in resulted concentrations NIPAM Higher Information). 43 to 29 from ranging temperature the concentrationstemperatureto variationmonitoredalso wasover nte iprat atr ro t uiiain f PNIPAM of utilization to prior factor important Another < 0.05, **p 0.05, < 0.01, and ***p and 0.01, ° < C. e) Diameter shrinkage ratio for ratio shrinkage Diameter e) C. 0.001). ° C (FigureC S3, Supporting DOI: 10.1002/adhm.201500357 DOI: www.MaterialsViews.com Adv.Mater.Healthcare NIPAM). d) Variation (10% w/v) (10%

2015 ° C - - - , FULL PAPER 5

, - - - R C, [20] / ° 2 V or C may be ° R 2 I = wileyonlinelibrary.com www.advhealthmat.de is the electrical current, electrical the is I and the generated heat could Ω a). A LightBlue Bean microcontroller board 5

C in initial hours followed by a reduced release rate ° is the resistance of the heater, heater, the of resistance the is Figure R is voltage). To activate the flexible heater and achieve a V To create an environment that supports the release of The microparticles were embedded inside a prepolymer solu has been reported in many drug we delivery expect that systems. soaking and However, thorough washing of particles can reduce the amount of this burst release to some extent. described in details in the Experimental Section (Figure 5c,d). As shown in Figure 5e, the temperature reached 35 ºC starting from 23 ºC in less than during the 1 delivery process. This system can be min later integrated and then it remained with stable a temperature sensor to enable a more precise ture adjustment. tempera water soluble factors while maintaining the moisture level where and stable temperature, a set of off-the-shelf electronic components were utilized. Current drive circuitry was used to power up the heater ( (Figure 5b) was also employed to control the programming driver the board applied by electrical current to the heater consequently and adjusting the hydrogel temperature. To the temperature control of thermoresponsive particles in the hydrogel sheet, a flexible heater was designed and microfabricated as The initial burst release is followed by observed diffusive shift in release. the The release profiles at 25 and due to initial 37 shrinkage of the microparticles and its significant effect on the burst release at a higher temperature. the particles showed a At burst release of almost 70% versus about 37 30% at 25 up to 72 h. tion which was directly casted on top of a flexible heater to min imize the interfacial thermal contact resistance. The resistance of the heater was around 80 be adjusted by tuning the applied current time or voltage duration and of the application (electrical power

------C over ° C and swelling at 2015 GmbH WILEY-VCH & Verlag Co. KGaA, Weinheim ° © Here, we studied the [19] C over the course of 48 h 70 000) from PNIPAM particles at different temperatures. c) Cumulative release of rhodamine isocyanate ° w M , 2015

Drug release from the thermoresponsive particles. a) Snapshot of release of FITC-dextran from particles incubated in PBS during heating. a, a set of time-lapse micrographs shows the release of

4

C before reaching a plateau. Higher concentrations of 536.08) from PNIPAM particles at different temperatures. ° w Cumulative release of FITC-dextran and rhodamine isocy There are various parameters that can affect the release We We also examined the swelling characteristics of different M Adv. Healthcare Mater. Adv. DOI: 10.1002/adhm.201500357 www.MaterialsViews.com Figure 4. b) Cumulative release of FITC-dextran ( ( anate from microparticles was measured at 25 and 37 the course of 72 h (Figure 4b). The results indicated an initial burst release of both drug models. The initial burst release was then mounted on a glass slide and placed inside the envi ronmental chamber of the microscope to observe the release of FITC-dextran in response to an increase in the temperature. phate-buffered phate-buffered saline (PBS) upon heating. For this purpose, a single FITC-dextran loaded microparticle was placed in a cavity on a transparent holder filled with 100 µL of PBS. The holder for treating skin infections. Both active molecules are fluores cent and can be easily detected using a spectrophotometer. In Figure FITC-dextran from a microparticle into the surrounding Phos many growth factors such as VEGF and KGF. In addition, we used rhodamine isocyanate with the molecular weight of 536.08 used antibiotics commercial some of range size the in is that Da process, and drug loading method constant. thiocyanate-dextran Fluorescein iso (FITC-dextran) with molecular weight 70 of kDa was used that has a molecular weight comparable to release profile of two drug weights models keeping the with particle size, different concentrations, crosslinking molecular kinetics and drug delivery properties. 37 NIPAM turned out to be more resistant to absorbance at both temperatures. assay (BS EN 13726-1) at 25 and 37 (Figure S4, Supporting Information). a The strong effect results of temperature indicated on the PNIPAM, absorbance showing capacity initial shrinking of at 25 concentrations of PNIPAM in a test solution with position ionic com comparable to human serum following standardized FULL PAPER 6 wileyonlinelibrary.com www.advhealthmat.de of the integrated microcontroller (LightBlue Bean) and electronics. c) Fabrication process of the flexible heater on parylene. d) Optical image of the min. 2 heater.over of flexible Transientheater microfabricated e) the image of response Optical d) parylene. on heater flexible the of Fabricationprocess c) electronics. and Bean) (LightBlue microcontroller integrated the of 5. Figure particle laden hydrogel patch in a flat Polydimethylsiloxane Polydimethylsiloxane flat a in patch hydrogel laden micro the particle of crosslinking for patch. out carried hydrogel steps the describes alginate-based were an microparticles in loaded drug embedded Thus, create patch. to sheet dermal hydrogel wet a a employed we area, wound the in

The electronic components and the fabrication method for the flexible patch system. a) Photograph of the heater circuitry. b) Photograph circuitry.b) heater the of Photograph a) system. patch flexible the for method fabrication the and components electronic The © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimCo.KGaA, Verlag& WILEY-VCH GmbH 2015 Figure

6 a - were covered with a flat sheet of agarose gel containing containing gel agarose of sheet flat a CaCl with microparticles covered and were (Na-alginate) alginate sodium of mixture the sheet, hydrogel the Toof mold. flatness (PDMS) the ensure y xhnig Na exchanging by 2 aqueous solution. The Na-alginate was crosslinked crosslinked was Na-alginate The solution. aqueous + with Ca 2 + to form a hydrogel network of DOI: 10.1002/adhm.201500357 DOI: www.MaterialsViews.com Adv.Mater.Healthcare

2015 ,

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- - wileyonlinelibrary.com www.advhealthmat.de bled on a 3D-printed TangoPlus flexible substrate (Figure 6d) to provide a conformal contact between the dermal patch and the body (Figure 6e). Incorporating different drug models the microparticles in validated the efficient release of drugs from the particles embedded in the alginate resents sheet. the Figure 6f fluorescent rep micrograph of released rhodamine upon heating from particles isocyanate embedded in the alginate sheet, where an increase in the fluorescent intensity could be hydrogel sheet adhered well to the heater 6c). (Figure The drug- loaded patch, the heater, and the microcontroller were assem

- - - - - 2015 GmbH WILEY-VCH & Verlag Co. KGaA, Weinheim © , 2015

The integrated platform for epidermal drug delivery. a) Schematic illustration of the fabrication steps for the hydrogel patch. b) Top view of the of view Top b) patch. hydrogel the for steps fabrication the of illustration Schematic a) delivery. drug epidermal for platform integrated The

Adv. Healthcare Mater. Adv. DOI: 10.1002/adhm.201500357 www.MaterialsViews.com ments. To minimize the thermal contact resistance between dif between resistance contact thermal the minimize To ments. ferent layers, the flexible heater was placed at the bottom of the PDMS mold during the hydrogel fabrication process. Thus, the The process enabled us to fabricate hydrogel sheets with ferent dif thicknesses. An alginate sheet 800 µm was found to be flexible yet strong enough to form con with the thickness of formal contact with skin and was used throughout the experi calcium alginate. Figure 6b represents the fluorescent micro graph of a typical alginate sheet with embedded monodisperse PNIPAM microparticles that were loaded with FITC-dextran. representative image showing the conformal contact of the engineered patch to skin. f)embedded particles from FITC-dextran of release Cumulative g) Fluorescence heater. image electric the by heated showing being after patch alginate the rhodamine in embedded particles from isocyanate release in the alginate patch. Figure 6. Figure microparticles, embedded with patch hydrogel the of view Close-up c) FITC-dextran. containing microparticles PNIPAM embedded with patch alginate integrated with d) the The flexible assembled heater. parts including the loaded temperature hydrogel sensor patch, e) and heater, A micro controller. FULL PAPER 8 wileyonlinelibrary.com www.advhealthmat.de medd nie hdoe matrix. hydrogel a inside embedded were particles loaded drug hydrogel where studies the other of in reported effect as buffering the to attributed be can that burst initial restrained relatively a demonstrated particles lated to and hydrogel particular,In solution. PBS the in encapsu release hydrogel the the through diffuse to longer takes particles micro embedded the from discharged drug the microparticles, h soe f ees pol, seily n h fis 1 h (more h 12 first the in especially profile, release of slope in the difference considerable revealed profile release the of tion examina closer A rate. release the controlling on temperature of effect substantial the confirmed data release The adjusted. relatively be can rate release the thus and change will triggered be can that particles of number the and rate the temperature, applied the changing by Thus, uniform. be not will distribution temperature the encapsulated layer, hydrogel are insulating thermally particles a the within Since ºC. 32 micro around of response particles the in observed was change sharp a thus ºC, 32 around as is materials, NIPAM, thermoresponsive of for example temperature an critical The compared diffusion. molecules passive of release to demand on and system faster proposed the the is of advantage key The 6g). (Figure h 72 37 and 25 of temperatures constant at solution PBS a into it placing particle-laden by measured from was patch alginate FITC-dextran of release cumulative Percent particles. the surrounding hydrogel the of parts the in observed r rpre fr NPM atce ebde i PEGDA in embedded particles PNIPAM hydrogel. for reported are observations Similar 4b). in (Figure release particles FITC-dextran free to in comparison observed was delay h 24 a where 6g, Figure with agreement in is observation This drug. sulated can be seen that 24 h is required for alginate to release the encap within alginate hydrogel (Figure S5, Supporting Information). It encapsulated freely FITC-dextran of rate release the also measured We expected. as rates release the prolonged and reduced micro nonencapsulated of sheet alginate the in particles the embedding that whereas particles, to similar is microparticles to 25 from temperature SupportingInformation). (FigureS6, ºC 37 applied the changing by 50%) than cnrbtn mcaim n h release, the in mechanism contributing a is diffusion when transport drug on effect limiting rate a have can thickness hydrogel that reporting literature the in data the on Based rise. temperature to response of in effect sharinkage particle accelerating the after factor, main the as considered higher than the period of the release tests, release the of period the than higher relatively are alginate and Information) Supporting S4, (Figure PNIPAM of times degradation the Since degradation. polymer the and barriers polymer the through diffusion by mainly occur can release passive shrinking, microparticle by induced release ae ht oe utie rlae rfie cn e band by obtained be can profiles release sustained more that late 37 at incubation h 72 after sheet alginate an in embedded microparticles for 53% to reduced was amount this where microparticles self-standing for measured was drug the of 92% of release Cumulative microparticles. encapsulated the of distribution the as well as mobility limited to attributed partially be can hydrogel the in embedded those and particles layer.hydrogel the of thickness the controlling by tuned be can patch the of out drug the of time diffusion the h gnrl ees pol o te rg fo encapsulated from drugs the of profile release general The The difference between release profile of self-standing micro [21] vrl, oprd o h sse o self-standing of system the to compared Overall, [22] pr fo te drug the from Apart ° oe te ore of course the over C [24] [23] © ° . e lo specu also We C. e pclt that speculate we 2015 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimCo.KGaA, Verlag& WILEY-VCH GmbH 2015 diffusion can be can diffusion ------

in the outer surface of the hydrogel matrix. hydrogel the of surface outer the in located particles of number the reduce to approaches adopting ees o dfeet rg oes rm efsadn particles self-standing from models drug different of release efficient the demonstrated We concentrations. polymer ferent dif using spectrometry absorption UV–vis and characteristics particles’shrinking both monitoring through characterized was variation temperature to response their and process emulsion microfluidic using fabricated were carriers drug moresponsive ther monodisperse PNIPAM demonstration, concept of proof a As temperature. applied the controlling through rate release drug modulating of possibility encapsulated the offer sheets hydrogel within carriers demand drug on Thermoresponsive and delivery. controlled drug of possibility the enables it addi tion, In pathogens. from wound the skin protecting and the moisture maintain to ability the skin, the with conformability good including features attractive multiple offers platform This burns. and wounds chronic as such disorders skin treating for factors growth and drug required the release effectively could In this study, we engineered a topical drug delivery platform that Conclusions3. 4. Experimental Section Experimental 4. plat kinetics. these and rate release drug the over control efficient offer forms products, healing wound customary the of functions deliverydrugplatforms.smartwoundsusingtypical Besidesthe chronic and disorders skin of process healing the accelerating for monomers. other with NIPAM co-polymerizing by application the on based adjusted be could respond microparticles which to temperature critical Further,the patch. hydrogel thick the of the ness and particles the of composition the controlling by platform. wearable and flexible a on integrated all were components aforementioned The time. of period a over range main desired the at temperature patch to the tain ability the and time phase transient over short quite response a showed heater the of Characterization perature. laden tem patch the particle on control precise the provide that patch, on hydrogel mounted microcontroller and sensor, heater,temperature flexible a of comprised was platform posed pro The verified. was carriers drug the addition, of biocompatibility In the sheet. hydrogel in embedded microparticles and using a microfluidic flow-focusing device. A cylindrical capillary tube wascylindrical capillarymicrofluidictubeflow-focusing A device.a using fabricated were microparticles responsive thermally and Monodisperse Technologies.Life Invitrogen from obtained was reagent viability from cell PrestoBlue USA). CA, (Carlsbad, purchased were (penicillin/streptomycin) antibiotics and (1X), (EDTA) acid trypsin-Ethylenediaminetetraacetic 0.05% (FBS), NIPAM. of photocrosslinking for used was system illumination UV S2000 Omnicure An PI. as used was Chemicals) CIBA 2959, (Irgacure 1-(4-(hydroxyethoxy)phenyl)-2-methyl-1-propanone 2-hydroxy- USA). MO, Louis, (St. Aldrich Sigma from purchased were oil N,N agent crosslinking In conclusion, this study paves the way to develop new solutions tuned be could patch engineered the from release drug The Materials irprils arcto ad irflii Dvc Characterization Device Microfluidic and Fabrication Microparticles serum bovine fetal (DMEM), medium Eagle modified Dulbecco’s Sdu agnt, acu clrd (CaCl chloride calcium alginate, Sodium : ′ mtyeeiarlmd, grs, n mineral and agarose, -methylenebisacrylamide, DOI: 10.1002/adhm.201500357 DOI: www.MaterialsViews.com Adv.Mater.Healthcare 2 , NIPAM, ),

2015 ------: , FULL PAPER 9 C ° [5] C. ° C. : A localized May 10, 2015 ° cells per well. 3 August 12, 2015 Published online: 10 wileyonlinelibrary.com (2.5 mmol) with an with mmol) (2.5 × + 2 www.advhealthmat.de Received: Revised: was microfabricated on a Ω : : Swelling tests were performed 80% confluency. 80 ≈ ≈ (142 mmol) and Ca and mmol) (142 + : Human keratinocytes were cultured in a DMEM . Cells were passaged at 2 Cell Cell Studies The heater with resistance of (L293) driver current the control to used was (Arduino) microcontroller A Electronics Assembly into the Patch and Characterization Free Swell Absorbance Capacity Tests For cytotoxicity assessment, cells were trypsinized and then seeded in supplemented supplemented with 10% FBS and 1% penicillin/streptomycin at and 5% 37 CO bandage platform was heater, microparticle loaded fabricated hydrogel, a compact from assembly shelf of electronic a off-the- components covered microfabricated by a miniaturized flexible flexible system plastic was wearable casing. and The flexible and heater and stabilize the temperature could in the range of 32–37 activate the parylene-C substrate. First, a silicon wafer parylene-C, was using covered a by PDS2010 12 µm parylene room of coater temperature. An with adhesive 20 stencil g tape was of cutter patterned (Versa, VLS2.40) dimer by (power a at 40%, laser speed 20%) and was the attached parylene to substrate. Then, 15 nm chromium and 150 sputtered nm gold on was the substrate. The behind the flexible stencil microfabricated heater. was then peeled off, leaving and amount of the power transferred from noncontact to infrared thermometer (Cason, USA) the was used to heater. stabilize Moreover, feedback and calibrate the hydrogel temperature. Response was time to measured be is of that 2 (FLX930) min. The the were flexible heater and TangoPlus using microcontroller casing heater flexible on a 3D-printed integrated and point break the at elongation 218% with elastomer flexible extremely an Young’s modulus of 1.5 MPa, which is comparable to human epidermis. ionic composition comparable ionic to comparable composition human serum and wound exudate, as samples the point time each At standard. 13726-1 EN BS the by suggested were taken out of the solution, the excess solution on their surface was removed and the samples were weighed using a high precision scale. The free swell absorbance tests were carried out both at 25 and 37 Fellowship Fellowship (PIF). A.K., P.M., S.S., M.R.D., acknowledge and funding A.T. from the National Science Foundation Naval Research (EFRI-1240443), Young the National Investigator office Award, of and Institutes the National of Health DE021468, HL099073, EB008392). (HL092836, DE019024, EB012597, AR057837, Supporting Information Supporting Information is available from the from the author. Wiley Online Library or Acknowledgements contributed equally to this work. S.B. acknowledges funding S.B. and A.T. from MIT-Italy program (Progetto Rocca) and Polimi International Cells were Cells then of with treated quantities and PNIPAM different particles their metabolic activity was monitored using PrestoBlue The assay. blue stain PrestoBlue reagent was uptaken by fluorescing viable stain. cells The and extent reduced of to reduction a is cells’ The proliferation. directly assay was performed proportional on days to 1, 3, the and 5 as per and protocol colour the induced reduction recommended manufacturer’s reader. microplate 2 Synnergy UV/vis BioTek a using measured was change assesses following the approach This procedure suggested in BS Absorbency. of EN Aspects 13726-1: – Test Methods for Dressings Wound Primary the performance of the molds PDMS different wounds. of concentrations exudating heavily to PNIPAM moderately to when exposed it typically is were used to prepare samples of the same that shape in were soaked test solution samples and hydrogel size Crosslinked for hydrogels. different was an aqueous solution of Na 48-well polystyrene plates at the concentration of 5

: w C). M ° 530 nm; 536.08 Da) w em λ M ; 2% w/v) and 2 C. C. The PNIPAM ° and agarose sheet 2 2015 GmbH WILEY-VCH & Verlag Co. KGaA, Weinheim © 580 nm). A calibration curve 485 nm and em λ ex λ ) ) and the microparticles’ ambient was C. Microparticles were mixed with the 1 ° − : The thermoresponsive microparticles C to reduce the reaction rate. The UV ° ) or rhodamine isocyanate ( 1 − 543 nm and C min ° ex , λ ) and incubated for 24 h to swell and absorb the 1 2015

− : Freeze dried microparticles were weighed and to characterize their thermoresponsive behavior. thermoresponsive their characterize to [25] Hydrogel Patch Preparation As the temperature was increased, the PNIPAM particles shrink and Release Studies Characterization of the Thermoresponsive Behavior of the Microparticles The microparticles were collected in a Petri dish and then were Adv. Healthcare Mater. Adv. DOI: 10.1002/adhm.201500357 www.MaterialsViews.com normalized and converted to percentage cumulative release. In all release our experiments, a similar drug delivery system without the loaded drug was used as the background signal. was prepared by measuring the and intensities was of used known to concentrations determine models (FITC-dextran and rhodamine isocyanate). The results were then the concentration of the released drug loaded particles were then separately added to 2 mL PBS and containers multiple were kept at different 200 temperatures. µL At of each the time fluorescent supernatant point, intensity was (FITC-dextran: removed and used to measure its drug solution. Both reagents are fluorescent and can be detected using a UV–vis spectrophotometer. For both batches, the microparticles were then separated from the solution and washed in excess order drug to remove solution the from their surfaces. Similar weights (2 mg) of Na-alginate solution prior to use. sheet, To crosslink an and aqueous form solution of an calcium alginate chloride (CaCl were encapsulated solution within of sodium alginate an (Na-alginate; distilled 2% water alginate-based and w/v) stored at was 4 dissolved hydrogel in patch. A PNIPAM, the variations microparticles as of a function UV–vis of UV/vis monomer BioTek a determined were w/v%) (0.5–0.125 concentration PI and absorption concentration (4–10 w/v%) of the Synnergy 2 spectrophotometer over a range of temperatures (28–42 crosslinked become opaque. In order to investigate the response of the crosslinked 70 kDa) solution (1 mg mL solution (1 mg mL each case 40 particles were monitored and the images were later analyzed analyzed later were images the and monitored were particles 40 case each using ImageJ measured measured continuously by the thermometer placed in the For chamber. rhodamine isocyanate: off and stored. The alginate solution was mold and the sheet obtained from the solidified poured CaCl into another PDMS agarose (2% w/v) was poured in to a PDMS flat mold and left at room temperature for 30 min to solidify. The agarose sheet was then peeled soaked in either a fluorescein isothiocyanate-dextran (FITC-dextran, was used to cover the Na-alginate for few minutes until calcium alginate sheets were formed. microparticles at room temperature were put in multiwell plates and were then placed on a Zeiss Axio observer D1 microscope temperature The S (XL Zeiss). unit a equipped and heating chamber environmental with an was slowly increased (1 (TE2000-U, Nikon). The thermoresponse of the fabricated microparticles was characterized by raising their ambient temperature from 25 to 40 microparticles were then four times washed by centrifugation in in order DI to formation remove the water of excess the oil. and The particles and the particle the size surfactant effect were of monitored flow using rate an variation inverted on optical microscope photopolymerized through exposure to the UV temperature light around for 4 5 min, intensity was keepingset to 850 mW and the distance between the tip of the fiber optic cable and the Petri dish was set to 8 cm. The crosslinked using using plastic syringes (BD connected Biosciences) by chemical resistant clear PVC tubing The (Mcmaster-carr). flow rates of the solutions were finely controlled by syringe pumps (PHD 2000, Harvard Apparatus). of NIPAM (4%–10% w/v), N,N-methylene-bis-acrylamide (BIS, 0.3% w/v) of w/v), N,N-methylene-bis-acrylamide NIPAM (4%–10% continuous The w/v). (0.5% PI soluble water and agent, crosslinking the as 20% Span80. phase was v/v oil mineral of containing surfactant nonionic The two phases were injected into the inlets of the microfluidic device coaxially aligned within a channel fabricated in the PDMS device. The inner inner The device. PDMS the in fabricated channel a within aligned coaxially diameters of the injection tube and hexane/acetone a PDMS with channel were 360 and recrystallization by 820 µm, purified was NIPAM respectively. mixture (50/50 v/v). The dispersed inner phase was an aqueous solution FULL PAPER 10 wileyonlinelibrary.com www.advhealthmat.de [12] H. [10] [11] [9] [3] [2] [8] S. [7] M. [6] [5] [4] [1] M. Sonkusale, S. J. D.-H. a) W.B. 34 Adv.Deliv.Drug Rev. Khademhosseini, A. C. N. a) Technol.Today Pharm. imdcl icis n Sses of (iCS, EE Lausanne, IEEE, (BioCAS), Switzerland Conf. Systems and Circuits Biomedical P. H. A. b) W.B. a) Freq.electrics Control. L. J. 26 Pathol. J. Am. N. D. R. a) Schreml, S. Trans.Med. A. G. M. M. a) 19. Y. L. 2004 R. M. a) Lancet

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