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Bioinspired Polymeric High‐Aspect‐Ratio Particles with Asymmetric Janus Functionalities

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Bioinspired Polymeric High‐Aspect‐Ratio Particles with Asymmetric Janus Functionalities RESEARCH ARTICLE www.advnanobiomedres.com Bioinspired Polymeric High-Aspect-Ratio Particles with Asymmetric Janus Functionalities Joel A. Finbloom, Yiqi Cao, and Tejal A. Desai* and particles have been engineered with Polymeric particles with intricate morphologies and properties have been diverse morphologies and physicochemical developed based on bioinspired designs for applications in regenerative medi- properties for applications such as tissue [7,8] cine, tissue engineering, and drug delivery. However, the fabrication of particles engineering and drug delivery. However, the design of polymeric particles with asymmetric functionalities remains a challenge. Janus polymeric particles with asymmetric distributions of functional- are an emerging class of materials with asymmetric functionalities; however, they ities remains a challenge. Many examples are predominantly spherical in morphology, made from nonbiocompatible of materials with asymmetric regions materials, and made using specialized fabrication techniques. Herein non- of functionality are found throughout [9] spherical Janus particles inspired by high-aspect-ratio filamentous bacteriophage natural systems. Proteins have regiospe- fi are fabricated using polycaprolactone polymers and standard methods. Janus ci c functionalities and biochemical proper- ties, which lead to controlled assembly high-aspect-ratio particles (J-HARPs) are fabricated with a nanotemplating dynamics, enzymatic active sites, and spe- technique to create branching morphologies selectively at one edge of the cificbindingdomainsofantibodies.[10,11] particle. J-HARPs are fabricated with maleimide handles and modified with Viruses such as filamentous bacteriophage biomolecules such as proteins and biotin. Regioselective modification is observed contain multivalent displays of peptides at the tips of J-HARPs, likely due to the increased surface area of the branching on one end of the virus particle to enable directional binding to targets.[12] Such regions. Biotinylated J-HARPs demonstrate cancer cell biotin receptor targeting, natural systems have been engineered by – as well as directional crosslinking with spherical particles via biotin streptavidin researchers to create protein-based materi- interactions. Finally, maleimide J-HARPs are functionalized during templating to als with regiospecific bioconjugate chemis- contain amines exclusively at the branching regions and are dual-labeled tries, or to create biotechnologies such as orthogonally, demonstrating spatially separated bioconjugation. Thus, J-HARPs enzyme-linked immunosorbent assays and [9–13] represent a new class of bioinspired Janus materials with excellent regional phage display. However, asymmetric biofunctionalities remain difficult to achieve control over biofunctionalization. using exclusively synthetic materials. Janus particles are an emerging class of synthetic materials with asymmetric prop- erties that have shown promise for applica- 1. Introduction tions in drug delivery, diagnostic medicine, and tissue engineering.[14,15] Janus materials have attracted attention for Bioinspired materials have seen increasing use for applications their ability to display multiple biofunctional handles with in nanotechnology and biomedicine. Intricate materials have regional control to enable improved material biointerfaces[16,17] been reported using systems inspired by naturally occurring as cells can respond to biological cues in gradient-dependent bioadhesives, light-harvesting systems, and self-assembling bio- manners.[17,18] In the field of drug delivery, Janus particles have – materials, among others.[1 6] Bioinspired polymeric materials shown promise in dual drug delivery, enabling the codelivery of multiple bioactive compounds with independent rates of [19–21] Dr. J. A. Finbloom, Dr. Y. Cao, Prof. T. A. Desai release. “Theranostic” Janus materials have attracted atten- Department of Bioengineering and Therapeutic Sciences tion for their abilities to better control multiple cargo conjuga- University of California San Francisco tions onto a single particle carrier.[15,22] Also within the field 204 Byers Hall, 1700 4th Street, San Francisco, CA 94158, USA of drug delivery, Janus particles have enabled the development E-mail: [email protected] of micro- and nanomotors, with gas-producing catalysts at one The ORCID identification number(s) for the author(s) of this article end of a particle to enable directional active motion and the pen- can be found under https://doi.org/10.1002/anbr.202000057. etration of particles through biological barriers.[23] These Janus © 2021 The Authors. Advanced NanoBiomed Research published by particles can be made from either inorganic or polymeric Wiley-VCH GmbH. This is an open access article under the terms of materials and fabricated through a variety of methods, including the Creative Commons Attribution License, which permits use, modification of particles at surface interfaces, directed material distribution and reproduction in any medium, provided the original fl work is properly cited. assemblies, micro uidics, electrojetting, and biphasic Pickering emulsions.[14,15,24,25] Although some Janus particles have been DOI: 10.1002/anbr.202000057 developed using hybrid platforms of biodegradable synthetic Adv. NanoBiomed Res. 2021, 2000057 2000057 (1 of 6) © 2021 The Authors. Advanced NanoBiomed Research published by Wiley-VCH GmbH www.advancedsciencenews.com www.advnanobiomedres.com and biologically derived materials,[26] the majority of Janus par- templating times of 2–3 h, which provide sufficient time for ticles are spherical in morphology and composed of inorganic PCL to pass through the 20 nm branched porous region of nonbiodegradable materials or specially synthesized polymers. the Anodiscs. We therefore hypothesized that if a limited tem- We therefore set out to develop, using standard fabrication tech- plating occurs, PCL polymers would be retained partially within niques and commercially available biodegradable polymers, a the 20 nm branching porous region of the AAO template new class of nonspherical Janus particles inspired by the regional (Figure 1a). Upon solidification, AAO etching, and HARP functionalities of high-aspect-ratio filamentous bacteriophage. purification, particles would then bear those branching morphol- To create these bacteriophage-inspired Janus particles, we uti- ogies at one end, resembling the morphologies of high-aspect- lized polycaprolactone (PCL) high-aspect-ratio particles (HARPs), ratio filamentous bacteriophage. Fabrication conditions were an emerging class of materials which we recently reported on screened to facilitate limited templating and J-HARP formation, for applications in local immunomodulation and regenerative with optimized conditions observed using 10 kDa PCL templated – engineering.[27 29] By adapting the HARP nanotemplating at 60 C for 30 min prior to removal of the Anodiscs from fabrication process,[27] asymmetric Janus HARPs (J-HARPs) heat and subsequent cooling and etching. Helium ion micros- were fabricated with high-surface-area branching morphologies copy (HIM) revealed asymmetric J-HARPs with a branched mor- at one edge of the particles. J-HARPs bearing maleimide phology observed exclusively at one edge of the particles conjugation handles were fabricated and functionalized with (Figure 1b). biomolecules such as proteins and biotin, with predominant To engineer J-HARPs for biomolecule functionalization, – [27] modification observed at the branched region of the J-HARPs PCL2k maleimide was incorporated at 20 wt% into the due to its increased surface area. We further demonstrated J-HARP backbone during fabrication. Fluorescein isothiocya- the versatility of J-HARPs by fabricating particles with separate nate-labed bovine serum albumin (FITC-BSA) was used to test regions of orthogonal reactivities and regioselectively labeled material bioconjugation efficiencies (Figure 2a) as BSA contains [31] J-HARPs with two different fluorescent cargos. J-HARPs there- a reactive thiol to facilitate maleimide–thiol addition. fore represent a novel class of bioinspired materials made from Interestingly, predominant modification was observed at one readily available and biodegradable components and could see edge of the J-HARPs, corresponding to the end with branching use in diverse biomedical applications. morphologies (Figure 2b,c). This is likely due to the higher sur- face area on the branching region, which can increase the expo- sure of maleimide groups and subsequent bioconjugation [32,33] 2. Results and Discussion efficiencies. The regiospecific branching at one edge of the J-HARP therefore enabled asymmetric modification of the 2.1. Fabrication and Regioselective Labeling of J-HARPs particle in a gradient manner, with highest degrees of FITC- BSA observed at the branched region. Modification was quanti- J-HARPs were fabricated from biodegradable PCL polymers fied through analysis of fluorescence intensities along the length using a nanotemplating technique. We previously reported on of the J-HARPs, and a steep gradient of modification was the use of nanotemplating to fabricate symmetric PCL HARPs observed starting at 1 μm from the J-HARP edge of 10–20 μm length and 200 nm diameter.[27,29] PCL was spun (Figure 2d), corresponding to the point at which branching mor- cast into films and heated in contact with 20 nm porous anodic phologies begin to be observed on the particles. A set of symmet- aluminum oxide (AAO) Anodisc templates, causing melted PCL ric HARPs with maleimide
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