The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Chikara Ohtsuki - One of the best experts on this subject based on the ideXlab platform.
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modification of Polyglutamic Acid with silanol groups and calcium salts to induce calcification in a simulated body fluid
Journal of Biomaterials Applications, 2011Co-Authors: Chikara Ohtsuki, Toshiki MiyazakiAbstract:The formation of hydroxyapatite is important for artificial materials to show high biological affinities for bone tissue. The present study focused on the synthesis of hydrogels capable of showing apatite formation, through modification of Polyglutamic Acid (PGA) with 3-aminopropyltriethoxysilane (APTES), followed by treatment with calcium chloride solution. A transparent bulk hydrogel was obtained at a molar ratio of PGA/APTES of 0.5. Prior soaking of the PGA hydrogel in calcium chloride solution accelerated the formation of bone-like apatite in a simulated body fluid. The modified PGA hydrogel is a candidate material for a biodegradable scaffold for bone regeneration.
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Apatite-forming ability of Polyglutamic Acid hydrogels in a body-simulating environment
Journal of Materials Science: Materials in Medicine, 2008Co-Authors: Atsushi Sugino, Toshiki Miyazaki, Chikara OhtsukiAbstract:Artificial joints can replace damaged joints provided the surrounding bone is sufficiently dense. However, elderly patients generally have reduced osteoporosis-associated bone density. Therefore, restitution of bone density is essential to ensure implantation. Injectable and resorbable bioactive fillers with bone-bonding ability (osteoconductivity) are promising, as osteoporosis can be reversed with minimal invasion. Osteoconduction occurs through the surface formation of biologically active hydroxyapatite via reactions with body fluids. Heterogeneous nucleation of the hydroxyapatite is catalysed by specific surface functional groups. In addition, release of Ca^2+ ions into the surrounding fluids enhances apatite nucleation by increasing its degree of supersaturation. We tested injectable bioactive filler made from cross-linked Polyglutamic Acid (PGA). This has many carboxyl groups that facilitate apatite nucleation. An insoluble hydrogel can be formed by cross-linkage. We exposed PGA gels to a simulated body fluid for 7 days. Trace amounts of calcium phosphate were formed, but were not identified as bone-like apatite by X-ray diffraction. However, formation of a bone-like apatite layer was detected using pre-treatment with CaCl_2 solutions (>0.01 mol dm^−3) dose dependently. Thus, this chemically cross-linked PGA gel could induce the heterogeneous nucleation of hydroxyapatite in a body environment, and this was enhanced by pre-treatment with CaCl_2.
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Apatite-Forming Ability of Polyglutamic Acid Gel in Simulated Body Fluid: Effect of Cross-Linking Agent
Key Engineering Materials, 2007Co-Authors: Atsushi Sugino, Toshiki Miyazaki, Chikara OhtsukiAbstract:Development of the organic-inorganic hybrids composed of apatite crystals and organic polymer is expected to be an attractive material that has mechanical properties similar to natural bone as well as bone-bonding ability, i.e. bioactivity. It is reported that the carboxyl groups (-COOH) on the surfaces of the organic substrates act as a catalyst for induction of heterogeneous nucleation of apatite. The present authors previously showed that the apatite was successfully deposited on the Polyglutamic Acid gels containing abundant carboxyl groups through the biomimetic process, when they were priorly treated with calcium chloride solution. In this study, we fabricated the Polyglutamic Acid gels with different degree of cross-linking. Effect of the cross-linking on their ability of the apatite formation was examined in simulated body fluid (SBF). It was suggested that the apatite deposition on the Polyglutamic Acid gels is governed not only by the amount of –COOH that induces the heterogeneous nucleation of the apatite, but also by swelling property that controls local increase in degree of supersaturation with respect to the apatite.
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Preparation of Apatite-Polyglutamic Acid Hybrid Through Biomimetic Process
Key Engineering Materials, 2006Co-Authors: Atsushi Sugino, Toshiki Miyazaki, Chikara Ohtsuki, Masao Tanihara, Koichi KuramotoAbstract:Natural bone has excellent mechanical properties such as high fracture toughness and high flexibility. These properties are achieved by specific microstructure of natural bone that is composed of the organic collagen and inorganic apatite. On the basis of these findings, apatite-polymer hybrids are expected as novel bone substitutes having excellent mehcanical performances and high bone-bonding ability, i.e. bioactivity. In this study, we attempted preparation of apatite-Polyglutamic Acid hybrids through biomimetic process that mimics the principle of biomineralization. Simple chemical modification of the Polyglutamic Acid gel with 1 M (= mol/L) calcium chloride solution provided the gel with apatite-forming ability in simulated body fluid (SBF, Kokubo solution). This type of hybrid is also useful for designing bioactive bone substitutes with injectability, since viscosity of the Polyglutamic Acid gel can be easily controlled according to degree of cross-linking.
Toshiki Miyazaki - One of the best experts on this subject based on the ideXlab platform.
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modification of Polyglutamic Acid with silanol groups and calcium salts to induce calcification in a simulated body fluid
Journal of Biomaterials Applications, 2011Co-Authors: Chikara Ohtsuki, Toshiki MiyazakiAbstract:The formation of hydroxyapatite is important for artificial materials to show high biological affinities for bone tissue. The present study focused on the synthesis of hydrogels capable of showing apatite formation, through modification of Polyglutamic Acid (PGA) with 3-aminopropyltriethoxysilane (APTES), followed by treatment with calcium chloride solution. A transparent bulk hydrogel was obtained at a molar ratio of PGA/APTES of 0.5. Prior soaking of the PGA hydrogel in calcium chloride solution accelerated the formation of bone-like apatite in a simulated body fluid. The modified PGA hydrogel is a candidate material for a biodegradable scaffold for bone regeneration.
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Apatite-forming ability of Polyglutamic Acid hydrogels in a body-simulating environment
Journal of Materials Science: Materials in Medicine, 2008Co-Authors: Atsushi Sugino, Toshiki Miyazaki, Chikara OhtsukiAbstract:Artificial joints can replace damaged joints provided the surrounding bone is sufficiently dense. However, elderly patients generally have reduced osteoporosis-associated bone density. Therefore, restitution of bone density is essential to ensure implantation. Injectable and resorbable bioactive fillers with bone-bonding ability (osteoconductivity) are promising, as osteoporosis can be reversed with minimal invasion. Osteoconduction occurs through the surface formation of biologically active hydroxyapatite via reactions with body fluids. Heterogeneous nucleation of the hydroxyapatite is catalysed by specific surface functional groups. In addition, release of Ca^2+ ions into the surrounding fluids enhances apatite nucleation by increasing its degree of supersaturation. We tested injectable bioactive filler made from cross-linked Polyglutamic Acid (PGA). This has many carboxyl groups that facilitate apatite nucleation. An insoluble hydrogel can be formed by cross-linkage. We exposed PGA gels to a simulated body fluid for 7 days. Trace amounts of calcium phosphate were formed, but were not identified as bone-like apatite by X-ray diffraction. However, formation of a bone-like apatite layer was detected using pre-treatment with CaCl_2 solutions (>0.01 mol dm^−3) dose dependently. Thus, this chemically cross-linked PGA gel could induce the heterogeneous nucleation of hydroxyapatite in a body environment, and this was enhanced by pre-treatment with CaCl_2.
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Apatite-Forming Ability of Polyglutamic Acid Gel in Simulated Body Fluid: Effect of Cross-Linking Agent
Key Engineering Materials, 2007Co-Authors: Atsushi Sugino, Toshiki Miyazaki, Chikara OhtsukiAbstract:Development of the organic-inorganic hybrids composed of apatite crystals and organic polymer is expected to be an attractive material that has mechanical properties similar to natural bone as well as bone-bonding ability, i.e. bioactivity. It is reported that the carboxyl groups (-COOH) on the surfaces of the organic substrates act as a catalyst for induction of heterogeneous nucleation of apatite. The present authors previously showed that the apatite was successfully deposited on the Polyglutamic Acid gels containing abundant carboxyl groups through the biomimetic process, when they were priorly treated with calcium chloride solution. In this study, we fabricated the Polyglutamic Acid gels with different degree of cross-linking. Effect of the cross-linking on their ability of the apatite formation was examined in simulated body fluid (SBF). It was suggested that the apatite deposition on the Polyglutamic Acid gels is governed not only by the amount of –COOH that induces the heterogeneous nucleation of the apatite, but also by swelling property that controls local increase in degree of supersaturation with respect to the apatite.
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Preparation of Apatite-Polyglutamic Acid Hybrid Through Biomimetic Process
Key Engineering Materials, 2006Co-Authors: Atsushi Sugino, Toshiki Miyazaki, Chikara Ohtsuki, Masao Tanihara, Koichi KuramotoAbstract:Natural bone has excellent mechanical properties such as high fracture toughness and high flexibility. These properties are achieved by specific microstructure of natural bone that is composed of the organic collagen and inorganic apatite. On the basis of these findings, apatite-polymer hybrids are expected as novel bone substitutes having excellent mehcanical performances and high bone-bonding ability, i.e. bioactivity. In this study, we attempted preparation of apatite-Polyglutamic Acid hybrids through biomimetic process that mimics the principle of biomineralization. Simple chemical modification of the Polyglutamic Acid gel with 1 M (= mol/L) calcium chloride solution provided the gel with apatite-forming ability in simulated body fluid (SBF, Kokubo solution). This type of hybrid is also useful for designing bioactive bone substitutes with injectability, since viscosity of the Polyglutamic Acid gel can be easily controlled according to degree of cross-linking.
Yasutaka Tahara - One of the best experts on this subject based on the ideXlab platform.
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structure of the hydrolyzed product f 2 released from γ Polyglutamic Acid by γ glutamyl hydrolase ywtd of bacillus subtilis
Bioscience Biotechnology and Biochemistry, 2006Co-Authors: Orawan Chunhachart, Tatsuhiro Hanayama, Momoe Hidesaki, Hiroyuki Tanimoto, Yasutaka TaharaAbstract:The structure of the hydrolyzed product (F-2) with a molecular mass of about 2 kDa released from γ-Polyglutamic Acid by the γ-glutamyl hydrolase YwtD of Bacillus subtilis was analyzed. The results showed that F-2 is an optically heterogeneous polymer consisting of D- and L-glutamic Acid in an 80:20 ratio with D-glutamic Acid on both the N- and C-terminal sides, suggesting that YwtD is an enzyme that cleaves the γ-glutamyl bond between D- and D-glutamic Acid recognizing adjacent L-glutamic Acid toward the N-terminal region.
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characterization of the bacillus subtilis ywtd gene whose product is involved in γ Polyglutamic Acid degradation
Journal of Bacteriology, 2003Co-Authors: Takao Suzuki, Yasutaka TaharaAbstract:The ywtD gene, which codes for an enzyme that degrades γ-Polyglutamic Acid (PGA), was cloned from Bacillus subtilis IFO16449. The gene is located immediately downstream of ywsC and ywtABC, a PGA operon involved in PGA biosynthesis, and it showed partial similarity to genes coding for dl-endopeptidase, a peptidoglycan-degrading enzyme. The ywtD gene, from which signal sequence is excised, was inserted into pET15b, and the recombinant plasmid was then transformed into Escherichia coli. Histidine-tagged YwtD was purified from sonicated cells of the transformant. The purified YwtD degraded PGA to yield two hydrolyzed products, a high-molecular-mass product (490 kDa with nearly 100% l-glutamic Acid) and an 11-kDa product (with d-glutamic Acid and l-glutamic Acid in an 80:20 ratio). This finding and results of enzymatic analysis of the two products with carboxypeptidase G suggest that YwtD is a novel enzyme cleaving the γ-glutamyl bond only between d- and l-glutamic Acids of PGA, and it may be designated γ-dl-glutamyl hydrolase.
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characterization of the bacillus subtilis ywsc gene involved in γ Polyglutamic Acid production
Journal of Bacteriology, 2002Co-Authors: Yuji Urushibata, Shinji Tokuyama, Yasutaka TaharaAbstract:The genes required for γ-Polyglutamic Acid (PGA) production were cloned from Bacillus subtilis IFO16449, a strain isolated from fermented soybeans. There were four open reading frames in the cloned 4.2-kb DNA fragment, and they were almost identical to those in the ywsC and ywtABC genes of B. subtlis 168. Northern blot analysis showed that the four genes constitute an operon. Three genes, ywsC, ywtA, and ywtB, were disrupted to determine which gene plays a central role in PGA biosynthesis. No PGA was produced in ΔywsC and ΔywtA strains, indicating that both of these genes are essential for PGA production. To clarify the function of the YwsC protein, histidine-tagged YwsC (YwsC-His) was produced in the ΔywsC strain and purified from the lysozyme-treated lysate of the transformant by Ni-nitrilotriacetic Acid affinity chromatography. Western blot analysis revealed that the YwsC-His protein consists of two subunits, the 44-kDa and 33-kDa proteins, which are encoded by in-phase overlapping in the ywsC gene. 14C-labeled PGA was synthesized by the purified proteins from l-[14C]-glutamate in the presence of ATP and MnCl2, through an acylphosphate intermediate, indicating that the ywsC gene encodes PGA synthetase (EC 6.3.2), a crucial enzyme in PGA biosynthesis.
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efficient production of γ Polyglutamic Acid by bacillus subtilis natto in jar fermenters
Bioscience Biotechnology and Biochemistry, 1997Co-Authors: Yoshihiro Ogawa, Fumio Yamaguchi, Katsumi Yuasa, Yasutaka TaharaAbstract:The large scale fermentation of γ-Polyglutamic Acid (γ-PGA) by Bacillus subtilis (natto) was done using a 30-liter jar fermenter. A stable cultivation without foaming could be done with addition of 3% NaCl to the medium. The γ-PGA productivity became higher with increasing speed of agitation and amounts of glutamic Acid added to the broth. Finally, we were able to obtain about 35 mg/ml of γ-PGA under the optimum conditions. The glutamic Acid added to the medium was efficiently converted into γ-PGA in the stationary phase. To discover the role of l-glutamic Acid added to the medium for γ-PGA biosynthesis by Bacillus subtilis (natto), the radioactivity incorporated into γ-PGA from 14C-l-glutamic Acid was measured. As a result, radioactive γ-PGA was detected in the medium. Then, the glutamic Acid in the medium was transported into the cells and actually polymerized as the glutamic Acid unit of γ-PGA.
Abhay Pandit - One of the best experts on this subject based on the ideXlab platform.
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the influence of size and charge of chitosan Polyglutamic Acid hollow spheres on cellular internalization viability and blood compatibility
Biomaterials, 2010Co-Authors: Biraja C Dash, Gildas Rethore, Michael G Monaghan, Kathleen T Fitzgerald, William M Gallagher, Abhay PanditAbstract:Abstract Polymeric hollow spheres can be tailored as efficient carriers of various therapeutic molecules due to their tunable properties. However, the entry of these synthetic vehicles into cells, their cell viability and blood compatibility depend on their physical and chemical properties e.g. size, surface charge. Herein, we report the effect of size and surface charge on cell viability and cellular internalization behaviour and their effect on various blood components using chitosan/Polyglutamic Acid hollow spheres as a model system. Negatively charged chitosan/Polyglutamic Acid hollow spheres of various sizes 100, 300, 500 and 1000 nm were fabricated using a template based method and covalently surface modified using linear polyethylene glycol and methoxyethanol amine to create a gradient of surface charge from negative to neutrally charged spheres respectively. The results here suggest that both size and surface charge have a significant influence on the sphere’s behaviour, most prominently on haemolysis, platelet activation, plasma recalcification time, cell viability and internalization over time. Additionally, cellular internalization behaviour and viability was found to vary with different cell types. These results are in agreement with those of inorganic spheres and liposomes, and can serve as guidelines for tailoring polymeric solid spheres for specific desired applications in biological and pharmaceutical fields, including the design of nanometer to submicron-sized delivery vehicles.
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The influence of size and charge of chitosan/Polyglutamic Acid hollow spheres on cellular internalization, viability and blood compatibility.
Biomaterials, 2010Co-Authors: Biraja C Dash, Gildas Rethore, Michael G Monaghan, Kathleen T Fitzgerald, William M Gallagher, Abhay PanditAbstract:Abstract Polymeric hollow spheres can be tailored as efficient carriers of various therapeutic molecules due to their tunable properties. However, the entry of these synthetic vehicles into cells, their cell viability and blood compatibility depend on their physical and chemical properties e.g. size, surface charge. Herein, we report the effect of size and surface charge on cell viability and cellular internalization behaviour and their effect on various blood components using chitosan/Polyglutamic Acid hollow spheres as a model system. Negatively charged chitosan/Polyglutamic Acid hollow spheres of various sizes 100, 300, 500 and 1000 nm were fabricated using a template based method and covalently surface modified using linear polyethylene glycol and methoxyethanol amine to create a gradient of surface charge from negative to neutrally charged spheres respectively. The results here suggest that both size and surface charge have a significant influence on the sphere’s behaviour, most prominently on haemolysis, platelet activation, plasma recalcification time, cell viability and internalization over time. Additionally, cellular internalization behaviour and viability was found to vary with different cell types. These results are in agreement with those of inorganic spheres and liposomes, and can serve as guidelines for tailoring polymeric solid spheres for specific desired applications in biological and pharmaceutical fields, including the design of nanometer to submicron-sized delivery vehicles.
Argyrios Margaritis - One of the best experts on this subject based on the ideXlab platform.
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production of stable quinine nanodispersions using esterified γ Polyglutamic Acid biopolymer
Biochemical Engineering Journal, 2013Co-Authors: Christoph Hoennscheidt, Argyrios Margaritis, Dirk Kreyenschulte, Rainer KrullAbstract:Novel methods are needed for the development of nanodispersed drug formulations to enhance bioavailability of many hydrophobic pharmaceuticals. The poorly water-soluble quinine is a well-known anti-malaria drug which can be used as a promising model compound for the development of novel nanodispersed formulations. In addition to hydrophobic drug's own affecting properties, surfactants play an important role for the enhancement of their low bioavailability by preparing stable dispersions. Amphiphilic compounds can efficiently be used to stabilize colloidal fragments by preventing the precipitation or crystallization of poorly water-soluble active ingredients during fabrication. A novel biopolymer derivative based on the biotechnologically produced γ-Polyglutamic Acid (γ-PGA) from Bacillus licheniformis cultivation was developed for encapsulation of the active ingredient. High-molecular γ-PGA is an anionic polyelectrolyte that was optimized and modified with hydrophobic l-phenylalanine ethyl ester (l-PAE) to form an amphiphilic comb polymer P(γ-GA-r-l-PAE) with surfactive properties. The approach of the nanodispersion polymer concentration, molecular weight and grafting degree enables the efficient stabilization of the poorly water-soluble model drug. The research presented in this report indicates the potential benefits of hydrophobically modified γ-PGA and suggests its potential role in forming stable dispersions for future pharmaceutical applications.
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characterization and in vitro cytotoxicity of doxorubicin loaded γ Polyglutamic Acid chitosan composite nanoparticles
Biochemical Engineering Journal, 2013Co-Authors: Frank Hellmers, Rainer Krull, Peter J Ferguson, James Koropatnick, Argyrios MargaritisAbstract:Abstract In this study, γ-Polyglutamic Acid (γ-PGA) and chitosan (CS) nanoparticles were characterized as a carrier for the anti-cancer drug doxorubicin (DOX). Using ionic complexation between the positively charged DOX and the negatively charged polyelectrolyte γ-PGA, DOX:γ-PGA complexes were produced with an efficiency of approximately 99%. SEM micrographs demonstrated that the complexation of γ-PGA and DOX alone does not lead to the formation of nanoparticles and that the addition of a third component, chitosan, is required. Drug-loaded DOX:γ-PGA:CS nanoparticles were produced with particle sizes ranging from ~150 to ~630 nm. The stability of the DOX:γ-PGA:CS nanoparticles was examined by suspending the nanoparticles in different kinds of aqueous media. For the first time, in vitro studies with DOX-loaded nanoparticles demonstrated the cytotoxicity of the nanoparticles against a human oral squamous cell carcinoma cell line (HN-5a). Non-drug-loaded γ-PGA:CS nanoparticles did not display cytotoxic effects. It was shown that the encapsulated or surface-bound DOX did not lose its bioactivity and the prepared drug-loaded particles exhibited a considerable anti-proliferative activity against the human cancer cell line.
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controlled release of doxorubicin from doxorubicin γ Polyglutamic Acid ionic complex
Journal of Nanomaterials, 2010Co-Authors: Bhavik Manocha, Argyrios MargaritisAbstract:Formation of drug/polymer complexes through ionic interactions has proven to be very effective for the controlled release of drugs. The stability of such drug/polymer ionic complexes can be greatly influenced by solution pH and ionic strength. The aim of the current work was to evaluate the potential of γ-Polyglutamic Acid (γ-PGA) as a carrier for the anticancer drug, Doxorubicin (DOX). We investigated the formation of ionic complexes between γ-PGA and DOX using scanning electron microscopy, spectroscopy, thermal analysis, and X-ray diffraction. Our studies demonstrate that DOX specifically interacts with γ-PGA forming random colloidal aggregates and results in almost 100% complexation efficiency. In vitro drug release studies illustrated that these complexes were relatively stable at neutral pH but dissociates slowly under Acidic pH environments, facilitating a pH-triggered release of DOX from the complex. Hydrolytic degradation of γ-PGA and DOX/γ-PGA complex was also evaluated in physiological buffer. In conclusion, these studies clearly showed the feasibility of γ-PGA to associate cationic drug such as DOX and that is may serve as a new drug carrier for the controlled release of DOX in malignant tissues.
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production and characterization of γ Polyglutamic Acid nanoparticles for controlled anticancer drug release
Critical Reviews in Biotechnology, 2008Co-Authors: Bhavik Manocha, Argyrios MargaritisAbstract:γ-Polyglutamic Acid (γ-PGA) is a hydrophilic, biodegradable, and naturally available biopolymer produced by a number of microbial species, most commonly, the Bacillaceae family. Its biological properties such as nontoxicity, biocompatibility, and nonimmunogenicity qualify it as an important biomaterial in drug delivery applications. This review focuses mainly on the development of γ-PGA nanoparticles as drug delivery carriers for anticancer therapeutics. We discuss various techniques for the production and characterization of γ-PGA nanoparticles and controlled-release strategies. We also present a brief overview of the tumor physiology that forms the basis for the development of various targeted drug delivery approaches in cancer chemotherapy.
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microbial biosynthesis of Polyglutamic Acid biopolymer and applications in the biopharmaceutical biomedical and food industries
Critical Reviews in Biotechnology, 2007Co-Authors: Joerg Martin Buescher, Argyrios MargaritisAbstract:This review article provides an updated critical literature review on the production and applications of Polyglutamic Acid (PGA). α-PGA is synthesized chemically, whereas γ-PGA can be produced by a number of microbial species, most prominently various Bacilli. Great insight into the microbial formation of γ-PGA has been gained thanks to the development of molecular biological techniques. Moreover, there is a great variety of applications for both isoforms of PGA, many of which have not been discovered until recently. These applications include: wastewater treatment, food products, drug delivery, medical adhesives, vaccines, PGA nanoparticles for on-site drug release in cancer chemotherapy, and tissue engineering.