Green Synthesis of Gold Nanoparticles Using Upland Cress and Their Biochemical Characterization and Assessment.

This research focuses on the plant-mediated green synthesis process to produce gold nanoparticles (Au NPs) using upland cress (Barbarea verna), as various biomolecules within the upland cress act as both reducing and capping agents. The synthesized gold nanoparticles were thoroughly characterized using UV-vis spectroscopy, surface charge (zeta potential) analysis, scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX), atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray diffraction (XRD). The results indicated the synthesized Au NPs are spherical and well-dispersed with an average diameter ~11 nm and a characteristic absorbance peak at ~529 nm. EDX results showed an 11.13% gold content. Colloidal Au NP stability was confirmed with a zeta potential (ζ) value of -36.8 mV. X-ray diffraction analysis verified the production of crystalline face-centered cubic gold. Moreover, the antimicrobial activity of the Au NPs was evaluated using Gram-negative Escherichiacoli and Gram-positive Bacillus megaterium. Results demonstrated concentration-dependent antimicrobial properties. Lastly, applications of the Au NPs in catalysis and biomedicine were evaluated. The catalytic activity of Au NPs was demonstrated through the conversion of 4-nitrophenol to 4-aminophenol which followed first-order kinetics. Cellular uptake and cytotoxicity were evaluated using both BMSCs (stem) and HeLa (cancer) cells and the results were cell type dependent. The synthesized Au NPs show great potential for various applications such as catalysis, pharmaceutics, and biomedicine.

Calcium-oligochitosan-pectin microcarrier for colonic drug delivery.

Pectin-based hydrogel microcarriers have shown promise for drug delivery to the colonic region. Microcarriers must remain stable throughout the upper gastrointestinal tract for effective colonic delivery, an issue that traditional pectin-based microcarriers have faced. The positively-charged natural biopolymer oligochitosan and divalent cation Ca2+ were used to dually cross-link pectin-based hydrogel microcarriers to improve carrier stability through simulated gastric and intestinal environments. Microcarriers were characterized with Scanning Electron Microscope and Fourier-Transform Infrared analysis. An optical microscope was used to observe the change of microcarrier size and morphology over time in the simulated gastrointestinal environments. Fluorescently-labeled Dextran was used as a model drug for this system. Calcium-Oligochitosan-Pectin microcarriers exhibited relatively small drug release in the upper gastrointestinal regions and were responsive to the high pH and enzymatic activity of simulated colonic environment (over 94% release after 2 h), suggesting great potential for colonic drug delivery.

Design of a Novel Oxygen Therapeutic Using Polymeric Hydrogel Microcapsules Mimicking Red Blood Cells.

The goal of this research was to develop a novel oxygen therapeutic made from a pectin-based hydrogel microcapsule carrier mimicking red blood cells. The study focused on three main criteria for developing the oxygen therapeutic to mimic red blood cells: size (5-10 µm), morphology (biconcave shape), and functionality (encapsulation of oxygen carriers; e.g., hemoglobin (Hb)). The hydrogel carriers were generated via the electrospraying of the pectin-based solution into an oligochitosan crosslinking solution using an electrospinning setup. The pectin-based solution was investigated first to develop the simplest possible formulation for electrospray. Then, Design-Expert® software was used to optimize the production process of the hydrogel microcapsules. The optimal parameters were obtained through the analysis of a total of 17 trials and the microcapsule with the desired morphology and size was successfully prepared under the optimized condition. Fourier transform infrared spectroscopy (FTIR) was used to analyze the chemistry of the microcapsules. Moreover, the encapsulation of Hb into the microcapsule did not adversely affect the microcapsule preparation process, and the encapsulation efficiency was high (99.99%). The produced hydrogel microcapsule system shows great promise for creating a novel oxygen therapeutic.

Stability improvement and characterization of bioprinted pectin-based scaffold.

PURPOSE:: Bioprinting is an alternative method for constructing tissues/organs for transplantation. This study investigated the cross-linker influence and post-printing modification using oligochitosan and chitosan for stability improvement. METHODS:: Oligochitosan was tested as a novel cross-linker to replace Ca2+ for pectin-based bio-ink. Oligochitosan (2 kD) and different molecular weight of chitosan were used to modify the bioprinted scaffold. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were used to characterize the scaffolds. RESULTS:: Oligochitosan failed to serve as a viable cross-linker. Successful post-printing modification was confirmed by FTIR and SEM analyses. CONCLUSION:: Regarding post-modification, chitosan-treated scaffolds showed enhanced stability compared to untreated scaffolds. In particular, scaffolds modified with 150 kD chitosan exhibited the highest stability.

Design of artificial red blood cells using polymeric hydrogel microcapsules: hydrogel stability improvement and polymer selection.

PURPOSE: To improve the stability of pectin-oligochitosan hydrogel microcapsules under physiological conditions. METHODS: Two different approaches were examined: change of the cross-linker length and treatment of the hydrogel microcapsules with 150 Mm CaCl2. Replacement of pectin with alginate was also studied. RESULTS AND CONCLUSIONS: It was observed that the molecular weight of the cross-linker oligochiotsan had no significant improvement on microcapsule stability. On the other hand, the treatment of pectin-oligochitosan microcapsules with Ca2+ increased the microcapsule stability significantly. Different types of alginate were used; however, no red-blood-cell-shaped microcapsules could be produced, which is likely due to the charge-density difference between deprotonated pectin and alginate polymers.

Novel pectin-based carriers for colonic drug delivery.

Pectin-based hydrogel carriers have been studied and shown to have promising applications for drug delivery to the lower GI tract, especially to the colonic region. However, making sure these hydrogel carriers can pass through the upper GI tract and reach the targeted regions, after oral administration, still remains a challenge to overcome. A solution to this problem is to promote stronger cross-linking interactions within the pectin-based hydrogel network. The combined usage of a divalent cation (Ca(2+)) and the cationic biopolymer oligochitosan has shown to improve the stability of pectin-based hydrogel systems - suggesting that these two cross-linkers may be used to eventually help improve pectin-based hydrogel systems for colonic drug delivery methods.

Development of a microscale red blood cell-shaped pectin-oligochitosan hydrogel system using an electrospray-vibration method: preparation and characterization.

PURPOSE: To develop and characterize a microscale pectin-oligochitosan hydrogel microcapsule system that could be applied in such biological fields as drug delivery, cell immobilization/encapsulation, and tissue engineering. METHODS: Microscale pectin-oligochitosan hydrogel microcapsules were prepared by using the vibration/electrostatic spray method. The morphology and chemistry of the hydrogel microcapsules were characterized by using scanning electron microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR), respectively. The designed hydrogel microcapsule system was then used to study the responsiveness of the microcapsules to different simulated human body fluids as well as cell encapsulation. RESULTS: The designed hydrogel microcapsule system exhibited a large surface area-to-volume ratio (red blood cell-shaped) and great pH/enzymatic responsiveness. In addition, this system showed the potential for controlled drug delivery and three-dimensional cell culture. CONCLUSION: This system showed a significant potential not only for bioactive-agent delivery, especially to the lower gastrointestinal (GI) tract, but also as a three-dimensional niche for cell culture. In particular, the hydrogel microcapsule system could be used to create artificial red-blood-cells as well as blood substitutes.