Chitosan/alginate polyelectrolyte complex hydrogels by additive manufacturing for in vitro 3D ovarian cancer modeling

Polyelectrolyte complexes (PECs) are self-assembled systems formed from oppositely charged polymers, used to create hydrogels for cell culture. This work was aimed at additive manufacturing 3D hydrogels made of a PEC between chitosan (Cs) and alginate, as well as their investigation for in vitro 3D ovarian cancer modeling. PEC hydrogels stability in cell culture medium demonstrated their suitability for long-term cell culture applications. Higher in vitro viability of two human ovarian cancer cell lines was detected at different time points on PEC hydrogels than on Cs hydrogels, used as a control. In addition, during the 63-day culture experiment, cells effectively colonized the scaffolds while retaining their aggressive tumor characteristics. A significantly lower sensitivity to cisplatin and eugenol, also when combined, was observed in the developed 3D ovarian cancer models, in comparison to what was achieved in relevant 2D cell cultures. The obtained results demonstrated therefore the suitability of the developed scaffolds for in vitro investigation of tumor modeling.

A "cyclodextrin-salicylic acid-chitosan" bifunctional monomer magnetic hydrophilic imprinted sandwich gel for targeted adsorption and slow release of ginkgolic acid

This study aims to address the challenge of detoxifying ginkgolic acid and transform it from waste into a valuable resource. By using pseudo-template molecular imprinting technology to chemically modify polysaccharide materials, we developed a polysaccharide-based molecular imprinted material (MMCC-CD/CS-MIP) for the targeted separation and controlled release of ginkgolic acid. Under optimal conditions, MMCC-CD/CS-MIP demonstrated excellent adsorption performance (Qmax = 47.786 mg g-1) and desorption performance (QD = 42.33 mg g-1), with a desorption rate of 88.58 %. In addition, the material exhibited outstanding selectivity, stability, recyclability, antibacterial activity, and sustained-release properties, with a cumulative release rate of 95.57 % over 72 h. The release data followed the Korsmeyer-Peppas model, while the adsorption behavior fit a multi-layer heterogeneous adsorption model (Freundlich model) and conformed to a second-order kinetic model. Thermodynamic analysis confirmed that the adsorption of ginkgolic acid by MMCC-CD/CS-MIP is both feasible and spontaneous. MMCC-CD/CS-MIP provides a promising solution for the detoxification of medicinal components.

Ionically-crosslinked carboxymethyl chitosan scaffolds by additive manufacturing for antimicrobial wound dressing applications

Chitosan chemical functionalization is a powerful tool to provide novel materials for additive manufacturing strategies. The main aim of this study was the employment of computer-aided wet spinning (CAWS) for the first time to design and fabricate carboxymethyl chitosan (CMCS) scaffolds. For this purpose, the synthesis of a chitosan derivative with a high degree of O-substitution (1.07) and water soluble in a large pH range allowed the fabrication of scaffolds with a 3D interconnected porous structure. In particular, the developed scaffolds were composed of CMCS fibers with a small diameter (< 60 μm) and a hollow structure due to a fast non solvent-induced coagulation. Zn2+ ionotropic crosslinking endowed the CMCS scaffolds with stability in aqueous solutions, pH-sensitive water uptake capability, and antimicrobial activity against Escherichia coli and Staphylococcus aureus. In addition, post-printing functionalization through collagen grafting resulted in a decreased stiffness (1.6 ± 0.3 kPa) and a higher elongation at break (101 ± 9 %) of CMCS scaffolds, as well as in their improved ability to support in vitro fibroblast viability and wound healing process. The obtained results encourage therefore further investigation of the developed scaffolds as antimicrobial wound dressing hydrogels for skin regeneration.

Chitosan/poly-γ-glutamic acid crosslinked hydrogels: Characterization and application as bio-glues

Ecofriendly hydrogels were prepared using chitosan (CH, 285 kDa) and two fractions of low molecular weight microbial poly-γ-glutamic acid (γ-PGA) (R1 and R2 of 59 kDa and 20 kDa, respectively). The hydrogels were synthesized through sustainable physical blending, employing three CH/γ-PGA mass ratios (1/9, 2/8, and 3/7), resulting in the formation of physically crosslinked materials. The six resulting CH/R1 and CH/R2 hydrogels were physico-chemically characterized and the ones with the highest yields (CH/R1 and CH/R2 ratio of 3/7), analyzed for rheological and morphological properties, showed to act as bio-glues on wood and aluminum compared to commercial vinyl- (V1) and acetovinyl (V2) glues. Lap shear analyses of CH/R1 and CH/R2 blends exhibited adhesive strength on wood, as well as adhesive/cohesive failure like that of V1 and V2. Conversely, CH/R2 had higher adhesive strength and adhesive/cohesive failure on aluminum, while CH/R1 showed an adhesion strength with adhesive failure on the metal similar to that of V1 and V2. Scanning electron microscopy revealed the formation of strong physical bonds between the hydrogels and both substrates. Beyond their use as bio-adhesives, the unique properties of the resulting crosslinked materials make them potentially suitable for various applications in paint, coatings, heritage preservation, and medical sector.

Theranostic nanogels: multifunctional agents for simultaneous therapeutic delivery and diagnostic imaging

In recent years, there has been a growing interest in multifunctional theranostic agents capable of delivering therapeutic payloads while facilitating simultaneous diagnostic imaging of diseased sites. This approach offers a comprehensive strategy particularly valuable in dynamically evolving diseases like cancer, where combining therapy and diagnostics provides crucial insights for treatment planning. Nanoscale platforms, specifically nanogels, have emerged as promising candidates due to their stability, tunability, and multifunctionality as carriers. As a well-studied subgroup of soft polymeric nanoparticles, nanogels exhibit inherent advantages due to their size and chemical compositions, allowing for passive and active targeting of diseased tissues. Moreover, nanogels loaded with therapeutic and diagnostic agents can be designed to respond to specific stimuli at the disease site, enhancing their efficacy and specificity. This capability enables fine-tuning of theranostic platforms, garnering significant clinical interest as they can be tailored for personalized treatments. The ability to monitor tumor progression in response to treatment facilitates the adaptation of therapies according to individual patient responses, highlighting the importance of designing theranostic platforms to guide clinicians in making informed treatment decisions. Consequently, the integration of therapy and diagnostics using theranostic platforms continues to advance, offering intelligent solutions to address the challenges of complex diseases such as cancer. In this context, nanogels capable of delivering therapeutic payloads and simultaneously armed with diagnostic modalities have emerged as an attractive theranostic platform. This review focuses on advances made toward the fabrication and utilization of theranostic nanogels by highlighting examples from recent literature where their performances through a combination of therapeutic agents and imaging methods have been evaluated.

Additive Manufacturing of Wet-Spun Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-Based Scaffolds Loaded with Hydroxyapatite

Tissue engineering represents an advanced therapeutic approach for the treatment of bone tissue defects. Polyhydroxyalkanoates are a promising class of natural polymers in this context thanks to their biocompatibility, processing versatility, and mechanical properties. The aim of this study is the development by computer-aided wet-spinning of novel poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-based composite scaffolds for bone engineering. In particular, PHBV scaffolds are loaded with hydroxyapatite (HA), an osteoinductive ceramic, in order to tailor their biological activity and mechanical properties. PHBV blending with poly(lactide-co-glycolide) (PLGA) is also explored to increase the processing properties of the polymeric mixture used for composite scaffold fabrication. Different HA percentages, up to 15% wt., can be loaded into the PHBV or PHBV/PLGA scaffolds without compromising their interconnected porous architecture, as well as the polymer morphological and thermal properties, as demonstrated by scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. In addition, HA loading results in increased scaffold compressive stiffness to levels comparable to those of trabecular bone tissue, as well as in higher in vitro MC3T3-E1 cell viability and production of mineralized extracellular matrix, in comparison to what observed for unloaded scaffolds. The observed mechanical and biological properties suggest the suitability of the developed scaffolds for bone engineering.

Additive manufacturing of wet-spun chitosan/hyaluronic acid scaffolds for biomedical applications

Additive manufacturing (AM) holds great potential for processing natural polymer hydrogels into 3D scaffolds exploitable for tissue engineering and in vitro tissue modelling. The aim of this research activity was to assess the suitability of computer-aided wet-spinning (CAWS) for AM of hyaluronic acid (HA)/chitosan (Cs) polyelectrolyte complex (PEC) hydrogels. A post-printing treatment based on HA chemical cross-linking via transesterification with poly(methyl vinyl ether-alt-maleic acid) (PMVEMA) was investigated to enhance the structural stability of the developed scaffolds in physiological conditions. PEC formation and the esterification reaction were investigated by infrared spectroscopy, thermogravimetric analysis, evolved gas analysis-mass spectrometry, and differential scanning calorimetry measurements. In addition, variation of PMVEMA concentration in the cross-linking medium was demonstrated to strongly influence scaffold water uptake and its stability in phosphate buffer saline at 37 °C. The in vitro cytocompatibility of the developed hydrogels was demonstrated by employing the murine embryo fibroblast Balb/3T3 clone A31 cell line, highlighting that PMVEMA cross-linking improved scaffold cell colonization. The results achieved demonstrated that the developed hydrogels represent suitable 3D scaffolds for long term cell culture experiments.

Novel multifunctional environmentally friendly degradable zeolitic imidazolate frameworks@poly (γ-glutamic acid) hydrogel with efficient dye adsorption function

Recently, metal-organic frameworks (MOFs) have been widely developed due to the rich porosity, excellent framework structure and multifunctional nature. Meanwhile, a series of MOFs crystals and MOF-based composites have been emerged. However, the widespread applications of MOFs are hindered by challenges such as rigidity, fragility, solution instability, and processing difficulties. In this study, we addressed these limitations by employing an in-situ green growth approach to prepare a zeolitic imidazolate frameworks-8@poly (γ-glutamic acid) hydrogel (ZIF-8@γ-PGA) with hierarchical structures. This innovative method effectively resolves the inherent issues associated with MOFs. Furthermore, the ZIF-8@γ-PGA hydrogel is utilized for dye adsorption, demonstrating an impressive maximum adsorption capacity of 1130 ± 1 mg/g for methylene blue (MB). The adsorption behavior exhibits an excellent agreement with both the kinetic model and isotherm. Meanwhile, because the adsorbent raw materials are all green non-toxic materials, multiple applications of materials can also be realized. Significantly, the results of antibacterial experiments showed that the ZIF-8@γ-PGA hydrogel after in-situ growth of ZIF-8 had better antibacterial properties. Thus, the ZIF-8@γ-PGA hydrogel has great potential for development in wound dressings, sustained drug owing to its biocompatibility and antibacterial activity.

Biopolymer-metal composites for selective removal and recovery of waterborne orthophosphate

Orthophosphate (Pi) remediation from effluent serves to address global water security by preventing eutrophication. Herein, chitosan (C), alginate (Alg) and three respective metal systems (Fe3+, Al3+, Cu2+) were used to prepare binary (BMC) or ternary (TMC) metal composite adsorbents. Their physicochemical properties were analyzed through XPS, IR and TGA, while the adsorption properties of the composites were characterized via adsorption isotherms and single-point experiments in saline environmental water. Al-composites formed Al-O complexes, while Fe- and Cu-composites formed in the presence of the biopolymer backbone FeO(OH) and Cu2(OH)3NO3, respectively. While Al-composites showed the highest bound water fraction (up to 16%), the Cu-composites (Cu-TMC-N, CuC-BMC-N; where N = nitrate) revealed the lowest water content. Alginate-based binary composites showed slightly higher water content, as compared to ternary and binary chitosan composites. Among the four materials (Al-TMC-N, Fe-TMC-N, Cu-TMC-N and CuC-BMC-N), the Al-TMC showed the highest Pi selectivity over sulfate, along with high Pi removal-% even in a binary mixture (sulfate + orthophosphate) despite the presence of competitive anion species. Upon spiking saline groundwater samples with low Pi (5 mg/L) that contains 2060 or 6030 mg/g sulfate, Al-TMC-N showed the highest Pi selectivity, followed by Fe-TMC-N. This trend in adsorption of Pi among the various composites is understood based on the HSAB principle for the conditions employed in this study. Removal efficiencies of Pi above 60% in Well 1 (ca. 2000 mg/L sulfate) and above 30% in Well 3 (ca. 6030 mg/L sulfate). Herein, environmentally compatible and sustainable composite adsorbents were prepared that reveal selective Pi recovery from (highly) saline groundwater that can mitigate eutrophication in aqueous media.

Additive Manufacturing of Wet-Spun Polysulfone Medical Implants

Research on additive manufacturing (AM) of high-performance polymers provides novel materials and technologies for advanced applications in different sectors, such as aerospace and biomedical engineering. The present article is contextualized in this research trend by describing a novel AM protocol for processing a polysulfone (PSU)/N-methyl-2-pyrrolidone (NMP) solution into medical implant prototypes. In particular, an AM technique involving the patterned deposition of the PSU/NMP mixture in a coagulation bath was employed to fabricate PSU implants with different predefined shape, fiber diameter, and macropore size. Scanning electron microscopy (SEM) analysis highlighted a fiber transversal cross-section morphology characterized by a dense external skin layer and an inner macroporous/microporous structure, as a consequence of the nonsolvent-induced polymer solidification process. Physical-chemical and thermal characterization of the fabricated samples demonstrated that PSU processing did not affect its macromolecular structure and glass-transition temperature, as well as that after post-processing PSU implants did not contain residual solvent or nonsolvent. Mechanical characterization showed that the developed PSU scaffold tensile and compressive modulus could be changed by varying the macroporous architecture. In addition, PSU scaffolds supported the in vitro adhesion and proliferation of the BALB/3T3 clone A31 mouse embryo cell line. These findings encourage further research on the suitability of the developed processing method for the fabrication of customized PSU implants.

Physicochemical Characterization of Chitosan/Poly-γ-Glutamic Acid Glass-like Materials

This paper sets up a new route for producing non-covalently crosslinked bio-composites by blending poly-γ-glutamic acid (γ-PGA) of microbial origin and chitosan (CH) through poly-electrolyte complexation under specific experimental conditions. CH and two different molecular weight γ-PGA fractions have been blended at different mass ratios (1/9, 2/8 and 3/7) under acidic pH. The developed materials seemed to behave like moldable hydrogels with a soft rubbery consistency. However, after dehydration, they became exceedingly hard, glass-like materials completely insoluble in water and organic solvents. The native biopolymers and their blends underwent comprehensive structural, physicochemical, and thermal analyses. The study confirmed strong physical interactions between polysaccharide and polyamide chains, facilitated by electrostatic attraction and hydrogen bonding. The materials exhibited both crystalline and amorphous structures and demonstrated good thermal stability and degradability. Described as thermoplastic and saloplastic, these bio-composites offer vast opportunities in the realm of polyelectrolyte complexes (PECs). This unique combination of properties allowed the bio-composites to function as glass-like materials, making them highly versatile for potential applications in various fields. They hold potential for use in regenerative medicine, biomedical devices, food packaging, and 3D printing. Their environmentally friendly properties make them attractive candidates for sustainable material development in various industries.

3D Printing of Layered Structures of Metal-Ionic Polymers: Recent Progress, Challenges and Opportunities

Layered Structures of Metal Ionic Polymers, or Ionic Polymer-Metal Composites (IPMCs) are formed by a membrane of an ionic electroactive materials flanked by two metal electrodes on both surfaces; they are devices able to change their shape upon application of an electrical external stimulus. This class of materials is used in various fields such as biomedicine, soft robotics, and sensor technology because of their favorable properties (light weight, biocompatibility, fast response to stimulus and good flexibility). With additive manufacturing, actuators can be customized and tailored to specific applications, allowing for the optimization of performance, size, and weight, thus reducing costs and time of fabrication and enhancing functionality and efficiency in various applications. In this review, we present an overview of the newest trend in using different 3D printing techniques to produce electrically responsive IPMC devices.

Combined use of novel chitosan-grafted N-hydroxyethyl acrylamide polyurethane and human dermal fibroblasts as a construct for in vitro-engineered skin

A rich plethora of information about grafted chitosan (CS) for medical use has been reported. The capability of CS-grafted poly(N-hydroxyethyl acrylamide) (CS-g-PHEAA) to support human dermal fibroblasts (HDFs) in vitro has been proven. However, CS-grafted copolymers lack good stiffness and the characteristic microstructure of a cellular matrix. In addition, whether CS-g-PHEAA can be used to prepare a scaffold with a suitable morphology and mechanical properties for skin tissue engineering (STE) is unclear. This study aimed to show for the first time that step-growth polymerizations can be used to obtain polyurethane (PU) platforms of CS-g-PHEAA, which can also have enhanced microhardness and be suitable for in vitro cell culture. The PU prepolymers were prepared from grafted CS, polyethylene glycol, and 1,6-hexamethylene diisocyanate. The results proved that a poly(saccharide-urethane) [(CS-g-PHEAA)-PU] could be successfully synthesized with a more suitable microarchitecture, thermal properties, and topology than CS-PU for the dynamic culturing of fibroblasts. Cytotoxicity, proliferation, histological and immunophenotype assessments revealed significantly higher biocompatibility and cell proliferation of the derivative concerning the controls. Cells cultured on (CS-g-PHEAA)-PU displayed a quiescent state compared to those cultured on CS-PU, which showed an activated phenotype. These findings may be critical factors in future studies establishing wound dressing models.

Redox-Responsive Hydrogels for Tunable and "On-Demand" Release of Biomacromolecules

In recent years, stimuli-responsive degradation has emerged as a desirable design criterion for functional hydrogels to tune the release of encapsulated payload as well as ensure degradation of the gel upon completion of its function. Herein, redox-responsive hydrogels with a well-defined network structure were obtained using a highly efficient thiol-disulfide exchange reaction. In particular, gelation occurred upon combining thiol-terminated tetra-arm polyethylene glycol (PEG) polymers with linear telechelic PEG-based polymers containing pyridyl disulfide units at their chain ends. Rapid gelation proceeds with good conversions (>85%) to yield macroporous hydrogels possessing high water uptake. Furthermore, due to the presence of the disulfide linkages, the thus-obtained hydrogels can self-heal. The obtained hydrogels undergo complete degradation when exposed to environments rich in thiol-containing agents such as dithiothreitol (DTT) and L-glutathione (GSH). Also, the release profile of encapsulated protein, namely, bovine serum albumin, can be tuned by varying the molecular weight of the polymeric precursors. Additionally, it was demonstrated that complete dissolution of the hydrogel to rapidly release the encapsulated protein occurs upon treating these hydrogels with DTT. Cytotoxicity evaluation of the hydrogels and their degradation products indicated the benign nature of these hydrogels. Additionally, the cytocompatible nature of these materials was also evident from a live/dead cell viability assay. One can envision that the facile fabrication and their ability to degrade on-demand and release their payload will make these benign polymeric scaffolds attractive for various biomedical applications.

Polymeric Hydrogels for In Vitro 3D Ovarian Cancer Modeling

Ovarian cancer (OC) grows and interacts constantly with a complex microenvironment, in which immune cells, fibroblasts, blood vessels, signal molecules and the extracellular matrix (ECM) coexist. This heterogeneous environment provides structural and biochemical support to the surrounding cells and undergoes constant and dynamic remodeling that actively promotes tumor initiation, progression, and metastasis. Despite the fact that traditional 2D cell culture systems have led to relevant medical advances in cancer research, 3D cell culture models could open new possibilities for the development of an in vitro tumor microenvironment more closely reproducing that observed in vivo. The implementation of materials science and technology into cancer research has enabled significant progress in the study of cancer progression and drug screening, through the development of polymeric scaffold-based 3D models closely recapitulating the physiopathological features of native tumor tissue. This article provides an overview of state-of-the-art in vitro tumor models with a particular focus on 3D OC cell culture in pre-clinical studies. The most representative OC models described in the literature are presented with a focus on hydrogel-based scaffolds, which guarantee soft tissue-like physical properties as well as a suitable 3D microenvironment for cell growth. Hydrogel-forming polymers of either natural or synthetic origin investigated in this context are described by highlighting their source of extraction, physical-chemical properties, and application for 3D ovarian cancer cell culture.

O-ATRP synthesized poly(β-pinene) blended with chitosan for antimicrobial and antioxidant bio-based films production

Antioxidant and antimicrobial activities are important characteristics of active film packaging designed to extend food preservation. In this study, functional bio-based films were produced using different concentrations of antioxidant poly(β-pinene) bio-oligomer synthesized via organocatalyzed atom transfer radical polymerization (O-ATRP) and blended with chitosan of different molecular weights. The structural, mechanical, thermal, solubility, antioxidant, and antimicrobial properties of the films were investigated. The poly(β-pinene)-chitosan blends presented significant pores and irregularities with the increase of poly(β-pinene) concentration over 30%. Chitosan molecular weight did not show any important influence in the physical properties of the blends. Poly(β-pinene) load decreased the materials' tensile strength and melting temperature, exhibiting a plasticizing effect on chitosan chains. The antioxidant and antimicrobial activities of the films were improved by poly(β-pinene) incorporation and mainly depended on its concentration. Therefore, the incorporation of poly(β-pinene) in chitosan films can be an alternative for active packaging production.

3D printable self-healing hyaluronic acid/chitosan polycomplex hydrogels with drug release capability

Multifunctional printable biomaterials are at the base of advanced biomedical applications. Chitosan (CHI) and hyaluronic acid (HA) allow the development of polycomplex hydrogels with tailorable properties, including self-healing and controlled drug release. This work correlates and optimizes the mucoadhesive, swelling, biodegradation, mechanical and rheological properties of HA/CHI polycomplex hydrogels with synthesis parameters such as polysaccharide content and complexation time, according to the interaction forces established between both polyelectrolytes. Related to these dynamic forces, the self-healing ability of the hydrogels was investigated together with the potential of the HA/CHI polycomplex hydrogels for 3D printing. Finally, their capability to modulate and promote controlled release of a variety of drugs (anionic and anti-inflammatory sodium diclofenac and the neutral antibiotic rifampicin) was demonstrated. Thus, the reported tunable properties, self-repair ability, printability and drug release properties, demonstrate the suitability of HA/CHI hydrogels for advanced biomedical applications.

An Overview of the Main Trends in the Creation of Biodegradable Polymer Materials

Plastic is one of the most demanded materials on the planet, and the increasing consumption of which contributes to the accumulation of significant amounts of waste based on it. For this reason, a new approach to the development of these materials has been formed: the production of polymers with constant operational characteristics during the period of consumption and capable of then being destroyed under the influence of environmental factors and being involved in the metabolic processes of natural biosystems. The paper outlines the prerequisites for the development of the field of creating biodegradable composite materials, as well as the main technical solutions for obtaining such polymeric materials. The main current solutions for reducing and regulating the degradation time of polymer materials are presented. The most promising ways of further development of the field of bioplastics production are described. Common types of polymers based on renewable raw materials, composites with their use, and modified materials from natural and synthetic polymers are considered.

A rapid and rapid method to quantify poly (γ-glutamic acid) content via copper ion complexation

Presently, there have been some limitations in most of methods to determine poly (γ-glutamic acid) (γ-PGA) content because of many impurities in test specimens. It is necessary to establish a rapid and accurate method to quantify γ-PGA content. In this work, γ-PGA and some impurities commonly seen in fermented broth like glucose, glutamic acid and proteins were used to complex with copper ions. The results show that only γ-PGA can make copper ion precipitated, which content linearly correlates with the precipitate amount. From the study on the validity of the method, it is found that the accuracy and precision are 95.82% and 99.29%, much higher than the ones of method UV and weighing. Therefore, the method via the complexation of copper ion will be popularized to determine γ-PGA content in crude biological samples.

Computer-Aided Wet-Spinning

Computer-aided wet-spinning (CAWS) has emerged in the past few years as a hybrid fabrication technique coupling the advantages of additive manufacturing in controlling the external shape and macroporous structure of biomedical polymeric scaffold with those of wet-spinning in endowing the polymeric matrix with a spread microporosity. This book chapter is aimed at providing a detailed description of the experimental methods developed to fabricate by CAWS polymeric scaffolds with a predefined external shape and size as well as a controlled internal porous structure. The protocol for the preparation of poly(ε-caprolactone)-based scaffolds with a predefined pore size and geometry will be reported in detail as a reference example that can be followed and simply adapted to fabricate other kinds of scaffold, with a different porous structure or based on different biodegradable polymers, by applying the processing parameters reported in relevant tables included in the text.

Biocompatible graft copolymers from bacterial poly(γ-glutamic acid) and poly(lactic acid)

Biocompatible graft copolymers from bacterial poly(γ-glutamic acid) and poly(lactic acid) are realized using a “grafting to” approach combined with click chemistry.

Recognition and selective extraction of poly-γ-glutamic acid based on molecular imprinting technology

Poly-γ-glutamic acid (γ-PGA) is one of the few bacterial polymers in nature with high added value of biodegradability. Especially, the traditional method of extracting γ-PGA is organic solvent extraction, etc., which has the disadvantages of low extraction rate and serious environmental pollution. With the expansion of γ-PGA industrial fermentation, an efficient and environmentally friendly method is required to be adopted. In this contribution, we report a novel method of separation of γ-PGA from fermentation broth based on molecular imprinting technology. The molecular imprinted polymer (MIP) was synthesized from chitosan (CS) and glutaraldehyde in the presence of γ-PGA. A nonimprinted polymer (NIP) was also synthesized by the same procedure in the absence of γ-PGA. The chemical structures and morphological structures of both MIP and NIP were examined by FTIR spectroscopy and scanning electron microscopy. The adsorption isotherms showed that the maximum adsorption capacity of MIP was 137.85 mg/g. The maximum adsorption capacity in the adsorption of NIP was 68.92 mg/g, which indicates that MIP shows specific selectivity for γ-PGA. A high saturated absorption capacity (Qmax=140.90 mg/g) was calculated from Freundlich isotherm equation. The imprinting factor of MIP was 4.76, indicating that MIP possess good recognition ability and selectivity for γ-PGA. The adsorption capacity decreased slightly (17.0%), which suggests the satisfactory reusability of γ-PGA after 5 cycles of reuse. Our study indicates that molecularly imprinted polymers present development prospects in the effective and selective separation of γ-PGA from fermentation broth compared with organic solvent precipitation.

Development of Injectable Thermosensitive Chitosan-Based Hydrogels for Cell Encapsulation

The three-dimensional complexity of the native extracellular matrix (ECM) suggests switching from 2D to 3D culture systems for providing the cells with an architecture more similar to the physiological environment. Reproducing the three-dimensionality in vitro can guarantee beneficial effects in terms of cell growth, adhesion, proliferation, and/or their differentiation. Hydrogels have the same tailorable physico-chemical and biological characteristics as ECM materials. In this study, we propose a thermoresponsive chitosan-based hydrogel that gels thanks to the addition of organic and inorganic salt solutions (beta-glycerolphosphate and sodium hydrogen carbonate) and is suitable for cell encapsulation allowing obtaining 3D culture systems. Physico-chemical analyses showed that the hydrogel formulations jellify at physiological conditions (37 °C, pH 7.4), are stable in vitro up to three weeks, have high swelling ratios and mechanical stiffness suitable for cellular encapsulation. Moreover, preliminary biological tests underlined the pronounced biocompatibility of the system. Therefore, these chitosan-based hydrogels are proposed as valid biomaterials for cell encapsulation.

Thiol-Reactive Clickable Cryogels: Importance of Macroporosity and Linkers on Biomolecular Immobilization

Macroporous cryogels that are amenable to facile functionalization are attractive platforms for biomolecular immobilization, a vital step for fabrication of scaffolds necessary for areas like tissue engineering and diagnostic sensing. In this work, thiol-reactive porous cryogels are obtained via photopolymerization of a furan-protected maleimide-containing poly(ethylene glycol) (PEG)-based methacrylate (PEGFuMaMA) monomer. A series of cryogels are prepared using varying amounts of the masked hydrophilic PEGFuMaMA monomer, along with poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate, a hydrophilic monomer and cross-linker, respectively, in the presence of a photoinitiator. Subsequent activation to the thiol-reactive form of the furan-protected maleimide groups is performed through the retro Diels-Alder reaction. As a demonstration of direct protein immobilization, bovine serum albumin is immobilized onto the cryogels. Furthermore, ligand-directed immobilization of proteins is achieved by first attaching mannose- or biotin-thiol onto the maleimide-containing platforms, followed by ligand-directed immobilization of concanavalin A or streptavidin, respectively. Additionally, we demonstrate that the extent of immobilized proteins can be controlled by varying the amount of thiol-reactive maleimide groups present in the cryogel matrix. Compared to traditional hydrogels, cryogels demonstrate enhanced protein immobilization/detection. Additionally, it is concluded that utilization of a longer linker, distancing the thiol-reactive maleimide group from the gel scaffold, considerably increases protein immobilization. It can be envisioned that the facile fabrication, conjugation, and control over the extent of functionalization of these cryogels will make these materials desirable scaffolds for numerous biomedical applications.

Preparation of water-soluble chitosan/poly-gama-glutamic acid-tanshinone IIA encapsulation composite and its in vitro/in vivo drug release properties

Some diseases could be treated by Tanshinone IIA (TA), which is an isolated component from the Chinese medicinal herb Tanshen (Salvia miltiorrhiza). However, the poor water solubility and low oral bioavailability of TA limited its clinical application. In this paper, TA was encapsulated by water - soluble chitosan/poly - γ - glutamic acid (WCS-γ-PGA) to improve its dissolution and oral bioavailability. The in vitro dissolution and in vivo metabolism of the encapsulated composite in rats were employed to evaluate the efficiency of the improvement. FTIR spectroscopy was applied to confirm the validity of encapsulation for TA by WCS-γ-PGA. The study's results showed that the optimal ratio of TA to drug carrier (WCS + γ-PGA) was 1:5.5 in weight with a reaction time of 1 h at room temperature for the encapsulation. The proper concentrations for WCS and TA in preparing the encapsulated composite using γ-PGA 0.125 mg ml^-1 were 6 mg ml^-1 and 1 mg ml^-1, respectively; The encapsulation efficiency and drug loading efficiency of WCS-γ-PGA-TA composite were (93.99 ± 2.20)% and (10.73 ± 0.75)%, respectively. The cumulative release of TA from the WCS-γ-PGA-TA encapsulated composite reached to 81% within 60 min, which was 5.56 times of that of the original TA in vitro dissolution. The peak concentration C_max of TA from the encapsulated composite in rat blood as measured by an ultracentrifugation test of an intra - gastric administration was 4.43 times that of the original TA concentration, and the area under the drug-time curve AUC _(0-t) and AUC _(0-∞) (p<0.01) of the WCS-γ-PGA-TA encapsulated composite were 4.56 and 4.20 times that of the original TA, respectively. It indicated that the encapsulation of TA with WCS-γ-PGA improved its solubility and bioavailability significantly.

Preliminary investigation on a new natural based poly(gamma-glutamic acid)/Chitosan bioink

The study aims to investigate a novel bioink made from Chitosan (Cs)/ poly(gamma-glutamic acid) (Gamma-PGA) hydrogel that takes advantage of the two biodegradable and biocompatible polymers meeting most of the requirements for biomedical applications. The bioink could be an alternative to other materials commonly used in 3D-bioprinting such as gelatin or alginate. Cs/ Gamma-PGA hydrogel was prepared by double extrusion of Gamma-PGA and Cs solutions, where 2 × 10⁵ human adult fibroblasts per ml Cs solution had been loaded, through Cellink 3D-Bioprinter at 37°C. A computer aided design model was used to get 3D-bioprinting of a four layers grid hydrogel construct with 70% infill. Hydrogel characterization involved rheology, FTIR analysis, stability study (mass loss [ML], fluid uptake [FU]), and cell retaining ability into hydrogel. 3D-bioprinted hydrogel gelation time resulted to be <60 s, hydrogel structure was maintained up to 36.79 Pa shear stress, FTIR analysis demonstrated Gamma-PGA/Cs interpolyelectrolyte complex formation. The 3D-bioprinted hydrogel was stable for 35 days (35% ML) in cell culture medium, with increasing FU. Cell loaded 3D-bioprinted Cs 6% hydrogel was able to retain 70% of cells which survived to printing process and cell viability was maintained during 14 days incubation.

“Clickable” bacterial poly(γ-glutamic acid)

The controlled functionalization of bacterial γ-PGA is realized through sonication, solubilization using quaternary ammonium salts and click chemistry.

Wet spinning and radial self-assembly of a carbohydrate low molecular weight gelator into well organized hydrogel filaments

In this work, we describe how a simple single low molecular weight gelator (LMWG) molecule - N-heptyl-d-galactonamide, which is easy to produce at the gram scale - is spun into gel filaments by a wet spinning process based on solvent exchange. A solution of the gelator in DMSO is injected into water and the solvent diffusion triggers the supramolecular self-assembly of the N-heptyl-d-galactonamide molecules into nanometric fibers. These fibers entrap around 97% of water, thus forming a highly hydrated hydrogel filament, deposited in a well organized coil and locally aligned. This self-assembly mechanism also leads to a very narrow distribution of the supramolecular fiber width, around 150 nm. In addition, the self-assembled fibers are oriented radially inside the wet-spun filaments and at a high flow rate, fibers are organized in spirals. As a result, this process gives rise to a high control of the gelator self-assembly compared with the usual thermal sol-gel transition. This method also opens the way to the controlled extrusion at room temperature of these very simple, soft, biocompatible but delicate hydrogels. The gelator concentration and the flow rates leading to the formation of the gel filaments have been screened. The filament diameter, its internal morphology, the solvent exchange and the velocity of the jet have been investigated by video image analysis and electron microscopy. The stability of these delicate hydrogel ropes has been studied, revealing a polymorphic transformation into macroscopic crystals with time under some storage conditions. The cell viability of a neuronal cell line on the filaments has also been estimated.

Chitosan-Chondroitin sulfate based polyelectrolyte complex for effective management of chronic wounds

Acute and chronic wound remain an unresolved clinical problem among various demographic groups. Traditional marketed products focus mainly on inhibition of bacterial growth at the wound site neglecting the tissue repair, which significantly affect the healing rate. It would be highly beneficial if a wound healing material can be developed which has both antibacterial as well as tissue regenerating potential. We have prepared a polyelectrolyte complex (PEC) using chitosan (CH) and chondroitin sulfate (CS) which can form an in-situ scaffold by spontaneous mixing. The fabrication of CH-CS PEC was optimized using Quality-By-Design (QbD) approach. The prepared PEC showed very high swelling and porosity property. It was found to be non-hemolytic with good blood compatibility and low blood clotting index. It also exhibited good antibacterial activity against both gram-positive and gram-negative bacteria. The cell proliferation study exhibited good cytocompatibility and almost four-fold increase in cell density when treated with CH-CS PEC compared to control. In summary, we demonstrated that the prepared CH-CS PEC showed good blood compatibility, high antibacterial effect, and promoted wound healing potentially by stimulating fibroblast growth, making it an ideal wound dressing material.

Role of Surfactants in the Properties of Poly(Ethylene Terephthalate)/Purified Clay Nanocomposites

Purified clay was modified with different amounts of alkyl ammonium and phosphonium salts and used as filler in the preparation of PET nanocomposites via melt intercalation. The effect of this type of filler on morphology and thermal and mechanical properties of PET nanocomposites was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analyses (TG), tensile properties, and transmission electron microscopy (TEM). The results showed that the mixture of alkyl ammonium and phosphonium salts favored the production of PET nanocomposites with intercalated and partially exfoliated morphologies with slight improvement in thermal stability. In addition, the incorporation of these organoclays tended to inhibit PET crystallization behavior, which is profitable in the production of transparent bottles.

Porous Polyelectrolytes: The Interplay of Charge and Pores for New Functionalities

The past decade has witnessed rapid advances in porous polyelectrolytes and there is tremendous interest in their synthesis as well as their applications in environmental, energy, biomedicine, and catalysis technologies. Research on porous polyelectrolytes is motivated by the flexible choice of functional organic groups and processing technologies as well as the synergy of the charge and pores spanning length scales from individual polyelectrolyte backbones to their nano-/micro-superstructures. This Review surveys recent progress in porous polyelectrolytes including membranes, particles, scaffolds, and high surface area powders/resins as well as their derivatives. The focus is the interplay between surface chemistry, Columbic interaction, and pore confinement that defines new chemistry and physics in such materials for applications in energy conversion, molecular separation, water purification, sensing/actuation, catalysis, tissue engineering, and nanomedicine.

Photopolymerized maleilated chitosan/thiol-terminated poly (vinyl alcohol) hydrogels as potential tissue engineering scaffolds

Photocrosslinkable hydrogels composed of natural materials exhibit great application potential in tissue engineering scaffolds. However, weak formation and poor mechanical property can usually be a limitation. Herein, the photo-clickable thiol-ene hydrogels based chitosan were synthesized using photopolymerization of maleic chitosan (MCS) and thiol-terminated poly (vinyl alcohol) (TPVA) in the presence of a biocompatible photoinitiator. Rheological property and absorbing behavior of the MCS/TPVA hydrogels could be tailored by varying the amount of TPVA in the feed. There was strong intermolecular hydrogen bonding between the molecules of MCS and TPVA. Notably, the MCS/TPVA hydrogel (MT-3) exhibited rapid gelation behavior (<120 s), improved stiff (G' = ∼5500 Pa) and compressive strength (0.285 ± 0.014 MPa), which were important for hydrogel scaffolds, especially for injectable hydrogel scaffolds. Photocrosslinked MCS/TPVA hydrogels was cytocompatible and could promote the L929 cells attachment and proliferation, showing their potential as tissue engineering scaffolds.

Design and fabrication of novel polymeric biodegradable stents for small caliber blood vessels by computer-aided wet-spinning

Biodegradable stents have emerged as one of the most promising approaches in obstructive cardiovascular disease treatment due to their potential in providing mechanical support while it is needed and then leaving behind only the healed natural vessel. The aim of this study was to develop polymeric biodegradable stents for application in small caliber blood vessels. Poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] (PHBHHx), a renewable microbial aliphatic polyester, and poly(ε-caprolactone), a synthetic polyester approved by the US Food and Drug Administration for different biomedical applications, were investigated as suitable polymers for stent development. A novel manufacturing approach based on computer-aided wet-spinning of a polymeric solution was developed to fabricate polymeric stents. By tuning the fabrication parameters, it was possible to develop stents with different morphological characteristics (e.g. pore size and wall thickness). Thermal analysis results suggested that material processing did not cause changes in the molecular structure of the polymers. PHBHHx stents demonstrated great radial elasticity while PCL stents showed higher axial and radial mechanical strength. The developed stents resulted able to sustain proliferation of human umbilical vein endothelial cells within two weeks of in vitro culture and they showed excellent results in terms of thromboresistivity when in contact with human blood.

Additive Manufacturing of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/poly(ε-caprolactone) Blend Scaffolds for Tissue Engineering

Additive manufacturing of scaffolds made of a polyhydroxyalkanoate blended with another biocompatible polymer represents a cost-effective strategy for combining the advantages of the two blend components in order to develop tailored tissue engineering approaches. The aim of this study was the development of novel poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/ poly(ε-caprolactone) (PHBHHx/PCL) blend scaffolds for tissue engineering by means of computer-aided wet-spinning, a hybrid additive manufacturing technique suitable for processing polyhydroxyalkanoates dissolved in organic solvents. The experimental conditions for processing tetrahydrofuran solutions containing the two polymers at different concentrations (PHBHHx/PCL weight ratio of 3:1, 2:1 or 1:1) were optimized in order to manufacture scaffolds with predefined geometry and internal porous architecture. PHBHHx/PCL scaffolds with a 3D interconnected network of macropores and a local microporosity of the polymeric matrix, as a consequence of the phase inversion process governing material solidification, were successfully fabricated. As shown by scanning electron microscopy, thermogravimetric, differential scanning calorimetric and uniaxial compressive analyses, blend composition significantly influenced the scaffold morphological, thermal and mechanical properties. In vitro biological characterization showed that the developed scaffolds were able to sustain the adhesion and proliferation of MC3T3-E1 murine preosteoblast cells. The additive manufacturing approach developed in this study, based on a polymeric solution processing method avoiding possible material degradation related to thermal treatments, could represent a powerful tool for the development of customized PHBHHx-based blend scaffolds for tissue engineering.