Supporting Information
Improvement in thermal stability of sucralose by γ-cyclodextrin metal-organic frameworks
Authors:
Nana Lv1,2,#, Tao Guo2,#, Botao Liu2,3,#, Caifen Wang2,#, Vikaramjeet Singh2, Xiaonan Xu1,2, Xue
Li1,4, Dawei Chen1,*, Ruxandra Gref4,*, Jiwen Zhang1,2*
Affiliations:
1 School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China;
2 Center for Drug Delivery System, Shanghai Institute of Materia Medica, Chinese Academy of
Sciences, Shanghai 201210, China;
3 School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai
201418, China;
4 Institute of Moléculaires Sciences d'Orsay, UMR CNRS 8214, Université Paris Sud,Université
Paris-Saclay, 91400 Orsay, France.
# The authors contribute equally. N.L. for loading, measurement other than HPLC and preparation
of manuscript; T.G. for molecular simulation; B.L. for CD-MOFs preparation; C.W. for HPLC
method establishment and validation.
Corresponding Authors:
Prof. Jiwen Zhang
Center for Drug Delivery Systems, Shanghai Institute of Materia Medica, Chinese Academy of
Sciences, No. 501 of Haike Road, Shanghai 201210, China; Tel: +86-21-20231980; E-mail: [email protected].
Prof. Ruxandra Gref
Institut Sciences Moléculaires Sciences d'Orsay, (UMR CNRS 8214), Universite´ Paris-Sud,
Université Paris-Saclay, 91400 Orsay, France; Tel: +33 (1)69158234; E-mail: ruxandra.gref@u- psud.fr.
Prof. Dawei Chen School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China; Tel: +86-24-
23986306; E-mail: [email protected]. S1. Determination of the sucralose by HPLC-ELSD
S2. Preparation of sucralose-γ-CD inclusion complex
S3. DSC curves of physical mixtures
S4. Release of sucralose from sucralose loaded neutralized CD-MOF-Nano in
ethanol
S5. Solid-state nuclear magnetic resonance (SSNMR)
S6. Molecular docking of sucralose and CD-MOFs S1. Determination of the sucralose by HPLC-ELSD
The amount of sucralose was determined by high performance liquid chromatography with evaporative light-scattering detection (HPLC-ELSD). Analysis was carried out with the Phenomenex C18 column (4.6 mm×150 mm, 5 μm i.d.), under the flow rate of 1.0 mL∙min-1, the injection volume of 20 μL, and the column temperature of 35°C. The mobile phase was composed of acetonitrile and water
(20:80, v/v). Sucralose were detected with an evaporative light-scattering detector, the temperature of drift tube was set as 70°C, the pressure of carrier gas (high purity nitrogen) was 3.3 bar and the gain was 6.
The results showed that reasonable linearity was achieved for all of the analytes over the range of 50-1000 μg•mL-1 with the correlation coefficients (R) greater than
0.998. The precision for sucralose were 5.39% and the recoveries of sucralose ranged from 94.6 to 101.8% at three spiked concentrations with the relative standard deviations (RSDs) lower than 4.9%. This method was fast, simple, sensitive and low cost, and has been successfully used to determine sucralose in our study. Sucralose and γ-CD released in the water solution while sucralose loaded CD-MOFs were dissolved, and they were completely separated using the HPLC-ELSD described above (Figure S1). Figure S1. HPLC chromatograms of sucralose (A), γ-CD (B) and sucralose loaded
CD-MOFs (C).
S2. Preparation of sucralose-γ-CD inclusion complex
Sucralose of 397 mg was dissolved in 15 mL of ethanol and then added to the stirred γ-CD aqueous solution (γ-CD of 1297 mg dissolved in pure water) drop by drop, with the temperature being maintained at 40 °C, wherein the molar ratio of sucralose to γ-CD was 1.0. The drug solution was then stirred continuously for 4 h.
Ethanol in the resulting clear solution was removed by rotary evaporation at 45 °C for
1 h, the remaining liquid was pre-frozen under -80 °C for 4 h and then lyophilized to obtain sucralose-γ-CD inclusion complex. The loading efficiency of sucralose in S-
CD was21.8±1.3 %.
S3. DSC curves of physical mixtures
Differential scanning calorimetry (DSC) was detected for physical mixtures of sucralose and neutralized CD-MOF-Nano or γ-CD, in which the sucralose content were the same as that for sucralose loaded neutralized CD-MOF-Nano or sucralose-γ- CD inclusion complex. The decomposition temperature for sucralose in physical mixtures was observed around 124°C, no delay of decomposition temperature was detected (Figure S2).
Figure S2. DSC curves of sucralose, γ-CD and physical mixtures of sucralose with
neutralized CD-MOF-Nano or γ-CD.
Table S1. Color changes of sucralose, CD-MOFs and sucralose loaded CD-MOFs
when exposed at 90°C for different time
Sample/Time 0 min 10 min 8 h Sucralose White Dark brown Dark brown CD-MOFs White White Light yellow Sucralose loaded CD-MOFs White White Light yellow
S4. Release of sucralose from sucralose loaded neutralized CD-MOF-Nano in ethanol
Sucralose loaded neutralized CD-MOF-Nano (wash or without wash) equivalent to 1 mg of sucralose were suspended in 5 mL of ethanol and maintained at 25 °C with a shaking rate of 100 rpm. Samples of 200 μL were withdrawn at predefined time intervals (0, 0.1, 0.2, 0.3, 0.5, 1, 2, 4, 6, 20 and 24 h) and the same volume of fresh
EtOH was added. The concentration of sucralose in each sample was determined by
HPLC-ELSD method described in section 2.5.4 and cumulative release percentage was calculated. Experiments were performed in triplicate.
For sucralose loaded neutralized CD-MOF-Nano without wash, about 65% of sucralose released within 1 h, for sucralose loaded neutralized CD-MOF-Nano washed with ethanol, only 30% of sucralose released under the same condition. The release kinetics of sucralose loaded neutralized CD-MOF-Nano (wash or without wash) satisfied the pseudo-second order model. Pseudo-second order kinetic equation(1) is as follows:
Wherein, t represents time, qt represents the release amount at time t, qe represents equilibrium release amount, k2 represents kinetic constant of pseudo- second order release.
The linear fitting equation and kinetic constant for sucralose loaded neutralized
CD-MOF-Nano without wash and the samples washed with ethanol were t/qt =
2 2 0.0014t + 0.0001 (R = 0.9989), k2 = 0.0196 and t/qt = 0.0022t + 0.0007 (R = 0.996), k2 = 0.0069, respectively. The fast release of the sucralose from sucralose loaded neutralized CD-MOF-Nano without wash might be due to the large fraction of sucralose adsorption on the surface of CD-MOFs. However, for sucralose loaded neutralized CD-MOF-Nano washed with ethanol, the majority of sucralose located in the interior of CD-MOFs, which may account for its relatively slow release in ethanol. Figure S3. Cumulative release curves (A) of sucralose loaded neutralized CD-MOF-
Nano (wash, without wash) in EtOH, and pseudo-second order kinetic fitting of the release parameters (B).
S5. Solid-state nuclear magnetic resonance (SSNMR)
Solid-state 13C cross-polarization/magic angle spinning (CP/MAS) spectra were collected on Agilent 600 MHz DD2 solid system, equipped with a 3.2 mm double- resonance MAS probe. The Hartmann-Hahn conditions of the CP experiment for acquiring 13C spectra were optimized by using adamantane. 13C NMR spectra were obtained at 6 kHz MAS spinning speed with a contact time of 1.0 ms. Recycle delay time for sucralose and γ-CD are 2 and 120 s, respectively. The 13C chemical shifts were externally referenced to tetramethylsilane (δ = 0.0 ppm).
No signal of sucralose was observed in sucralose loaded neutralized CD-MOF-
Nano wash (surface located sucralose were removed, sucralose weight content was
4.6%) and the NMR spectra of which was almost similar to the neutralized CD-MOF-
Nano (Figure S4). Whereas, the chemical shift of sucralose at chemical shifts (δ) of
93.3 was detected in physical mixture sample, wherein the weight content was also
4.6% (same as loaded one). The NMR spectra of sucralose loaded neutralized CD-
MOF-Nano without wash was similar to that of neutralized CD-MOF-Nano, however, the characteristic chemical shifts (δ) of sucralose at 91.4 ppm and 43.6 ppm were detected in loaded neutralized CD-MOF-Nano without wash.
Figure S4. 13C MAS NMR spectra of sucralose, neutralized CD-MOF-Nano,
sucralose loaded CD-MOF-Nano with wash, sucralose loaded neutralized CD-
MOF-Nano without wash and physical mixture of sucralose with neutralized
CD-MOF-Nano.
S6. Molecular docking of sucralose and CD-MOFs
Docking protocol was executed to the prepared sucralose model and CD-MOFs model. Then the docking with relatively low energy was used for energy optimization and molecular dynamics (MD), in which CD-MOFs model was fixed and all models were put in vacuum. In the MD protocol, the COMPASSII force field was adopted, and the NVT ensemble and the Berendsen temperature control method was employed for a total time of 50 ps. The nonbond cut-off distance of 18.5 Å, spline width of 1.0
Å and buffer width of 0.5 Å were used. In the task of minimization, a smart algorithm was employed with the total energy of the system converged to less than 2.0×10-5 kcal∙mol-1, the residual force to less than 0.001 kcal∙mol-1∙Å-1, the displacement of atoms to less than 1×10-5 Å. In the Vina, a Lamarckian genetic algorithm (LGA) in combination with a grid-based energy evaluation method were used for pre- calculating grid maps according to the interatomic potentials of all atom types present in the host and guest molecules, including the Lennard-Jones potentials for van der
Waals interactions and Coulomb potentials for electrostatic interactions. A grid map of dimensions 70×70×70 Å, with a grid spacing of 0.375 Å, was placed to cover the CD-
MOFs structure. With the help of AutoDockTools(2), the atomic partial charges were calculated by the Gasteiger–Marsili method(3). The parameters used for the global search were an initial population of 50 individuals, with a maximal number of energy evaluations of 1,500,000 and a maximal number of generations of 50,000 as an end criterion and other docking parameters were set as default.
For the docking of sucralose to one mole of γ-CD, the sucralose molecule was almost entirely included in γ-CD (docking free energy of -5.3 kcal∙mol-1), based on which, the second CD was docked (docking energy of -5.9 kcal∙mol-1) in the same pattern as that for sucralose in CD-MOFs. However, the distance between two γ-CDs were closer than that in CD-MOFs due to the stagger of γ-CDs in aqueous solution.
The sucralose molecule still stayed in the first γ-CD, and hardly entered the second γ-
CD, the docking interaction mainly derived from the electrostatic effect between the hydroxyls in γ-CDs. It can be estimated that sucralose was generally included in one
γ-CD in diluted solution, and more γ-CDs would be required for sucralose to be enclosed by two γ-CDs.
References
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