Crystallization Of L-Glutathione On Icrystal Plates Using Metal-Assisted And Microwave-Accelerated Evaporative Crystallization And A Mono-Mode Microwave
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Metal-Assisted and Microwave-Accelerated Evaporative Crystallization (MA-MAEC) is among the latest developments in the manufacture of biologically based crystalline drug compounds described by the Aslan Research Group. MA-MAEC is a technique that has the capacity to produce crystals with controlled properties within a very short time. To date, the use of MA-MAEC technique was demonstrated for the rapid crystallization of individual amino acids, small molecules and lysozyme using conventional microwave ovens. In this study, a tri-peptide, L-glutathione (GSH) was successfully crystallized on iCrystal plates via the MA-MAEC technique using a mono-mode microwave cavity to increase the effect of microwave heating for faster than ever crystallization of biological molecules as compared to conventional microwave ovens. The influence of various processing parameters such as solvent, microwave power level (200 - 1000 Watts), GSH concentration (0.3 - 0.5 g/mL) and substrate type (poly (methyl methacrylate) and silver nanoparticle films (SNFs)) was studied in order to help optimize the GSH crystallization process. Sodium acetate was found to be the best solvent for GSH crystallization because a higher concentration of GSH could be dissolved in this solvent compared to the other solvents. In addition, GSH crystals formed at a more rapid rate in sodium acetate solutions. The FTIR analysis reveals that crystals resulting from the MA-MAEC technique are GSH-based. GSH functional groups that were observed in the FTIR results include the thiol (-SH), a carboxyl group (COOH), carbonyl group C=O / 1713 cm−1 antisymmetric C=O, amine (-NH2/ NH), and 1397 cm−1, COO- /asymmetric, and 1713-1602 cm−1, -C-N / stretching. COO−), (asymmetric -COO−), (anti-symmetric -C = O) and (1280 cm−1 δOH) indicate the presence of a −COOH group, while the band assigned to a stretching 1075 cm−1 -C-N vibrational mode. The parameters that influenced GSH crystallization time were type of substrate, microwave power level, and the initial concentration of GSH. Initial GSH crystal formation was observed at approximately 5 minutes for all conditions. The minimum crystallization time of 40 ±13 minutes was achieved for the following conditions: 0.50 g/mL of GSH at the highest microwave power level of 1000 Watts on the SNFs surface. In addition, the comparison of the initial GSH studies using conventional microwave heating by the Aslan Research Group and using a mono-mode cavity and variable power microwave source (1,200 Watts) was carried out by comparing crystallization time measurements and crystal size data. GSH crystal size was observed to decrease by 50% or more with increasing concentration for both microwave systems. There was a notable difference in crystal size between GSH crystals grown on the iCrystal plates using both microwave systems based on the magnitude of the mean and standard deviation. This study provides evidence that the use of mono-mode microwave cavity affords superior growth of GSH crystals in terms speed and crystal quality and these results implies that future crystal growth studies should be carried out using a mono-mode cavity and mono-mode microwave source with variable power, especially for samples with low availability.