Purification and biocompatibility of fermented hyaluronic acid for its applications to biomaterials

"Three-in-one": A Photoactivable Nanoplatform Evokes Anti-Immune Response by Inhibiting BRD4-cMYC-PDL1 Axis to Intensify Photo-Immunotherapy

Combinatorial immuno-cancer therapy is recognized as a promising approach for efficiently treating malignant tumors. Yet, the development of multifunctional nanomedicine capable of precise tumor targeting, remote activation, and immune-regulating drug delivery remains a significant challenge. In this study, nanoparticles loaded with an immune checkpoint inhibitor (JQ-1) using polypyrrole/hyaluronic acid (PPyHA/JQ-1) are developed. These nanoparticles offer active tumor targeting, photothermal tumor ablation using near-infrared light, and laser-controlled JQ-1 release for efficient breast cancer treatment. When the molecular weight of HA varies (from 6.8 kDa to 3 MDa) in the PPyHA nanoparticles, it is found that the nanoparticles synthesized using 1 MDa HA, referred to as PPyHA (1 m), show the most suitable properties, including small hydrodynamic size, high surface HA contents, and colloidal stability. Upon 808 nm laser irradiation, PPyHA/JQ-1 elevates the temperature above 55 °C, which is sufficient for thermal ablation and active release of JQ-1 in the tumor microenvironment (TME). Notably, the controlled release of JQ-1 substantially inhibits the expression of cancer-promoting genes. Furthermore, PPyHA/JQ-1 effectively suppresses the expression of programmed cell death ligand 1 (PD-L1) and prolongs dendritic cell maturation and CD8+ T cell activation against the tumor both in vitro and in vivo. PPyHA/JQ-1 treatment simultaneously provides a significant tumor regression through photothermal therapy and immune checkpoint blockade, leading to a durable antitumor-immune response. Overall, "Three-in-one" immunotherapeutic photo-activable nanoparticles have the potential to be beneficial for a targeted combinatorial treatment approach for TNBC.

Polymeric functionalization of mesoporous silica nanoparticles: Biomedical insights

Mesoporous silica nanoparticles (MSNs) endowed with polymer coatings present a versatile platform, offering notable advantages such as targeted, pH-controlled, and stimuli-responsive drug delivery. Surface functionalization, particularly through amine and carboxyl modification, enhances their suitability for polymerization, thereby augmenting their versatility and applicability. This review delves into the diverse therapeutic realms benefiting from polymer-coated MSNs, including photodynamic therapy (PDT), photothermal therapy (PTT), chemotherapy, RNA delivery, wound healing, tissue engineering, food packaging, and neurodegenerative disorder treatment. The multifaceted potential of polymer-coated MSNs underscores their significance as a focal point for future research endeavors and clinical applications. A comprehensive analysis of various polymers and biopolymers, such as polydopamine, chitosan, polyethylene glycol, polycaprolactone, alginate, gelatin, albumin, and others, is conducted to elucidate their advantages, benefits, and utilization across biomedical disciplines. Furthermore, this review extends its scope beyond polymerization and biomedical applications to encompass topics such as surface functionalization, chemical modification of MSNs, recent patents in the MSN domain, and the toxicity associated with MSN polymerization. Additionally, a brief discourse on green polymers is also included in review, highlighting their potential for fostering a sustainable future.

Hyaluronic Acid Unveiled: Exploring the Nanomechanics and Water Retention Properties at the Single-Molecule Level

Hyaluronic acid (HA), a vital glycosaminoglycan in living organisms, possesses remarkable mechanical and viscoelastic properties that have garnered significant attention in therapeutic, biomedical, and cosmetic applications. However, a comprehensive picture of the physicochemical and biocharacterization of HA at the single-molecule level remains elusive. In this work, atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) and molecular dynamics (MD) simulation were used to investigate the nanomechanics and water retention properties of HA at the single-molecule level. The present study aims to unravel the intricate details of the influence of molecular structure on HA behavior and shed light on its unique attributes. According to the force measurements, the energy used to stretch a HA chain in water is 8.45 kJ/mol, significantly surpassing that of Curdlan (3.45 kJ/mol) and chitin (2.23 kJ/mol), both of which possess molecular structures partially similar to that of HA. Intriguingly, the strength of the intrachain interaction of HA (5.54 kJ/mol) was considerably weaker compared to Curdlan (11.06 kJ/mol) and chitin (or cellulose, 10.76 kJ/mol). This result indicates that HA exhibits a preference for interacting with water rather than with itself, thereby showing enhanced water affinity. Moreover, the force measurements demonstrated that changing the glycosidic bond from β-(1-3) (Curdlan) or β-(1-4) (chitin or cellulose) to β-(1-3) + β-(1-4) (HA) resulted in polysaccharides displaying improved water affinity and more extended conformation. These conclusions were further verified by molecular dynamics (MD) simulations. Overall, our work sheds new light on the nanomechanics and water retention properties of HA at the single-molecule level, offering valuable insights for future research in this field.

Tapping on the Potential of Hyaluronic Acid: from Production to Application

The manufacture, purification, and applications of hyaluronic acid (HA) are discussed in this article. Concerning the growing need for affordable, high-quality HA, it is essential to consider diverse production techniques using renewable resources that pose little risk of cross-contamination. Many microorganisms can now be used to produce HA without limiting the availability of raw materials and in an environmentally friendly manner. The production of HA has been associated with Streptococci A and C, explicitly S. zooepidemicus and S. equi. Different fermentation techniques, including the continuous, batch, fed-batch, and repeated batch culture, have been explored to increase the formation of HA, particularly from S. zooepidemicus. The topic of current interest also involves a complex broth rich in metabolites and residual substrates, intensifying downstream processes to achieve high recovery rates and purity. Although there are already established methods for commercial HA production, the anticipated growth in trade and the diversification of application opportunities necessitate the development of new procedures to produce HA with escalated productivity, specified molecular weights, and purity. In this report, we have enacted the advancement of HA technical research by analyzing bacterial biomanufacturing elements, upstream and downstream methodologies, and commercial-scale HA scenarios.

Downstream process intensification for biotechnologically generated hyaluronic acid: Purification and characterization

Hyaluronic acid (HA), an anionic, non-sulfated glycosaminoglycan, has several clinical applications. This study examines several downstream methods for purifying HA with maximum recovery and purity. Following the fermentation of Streptococcus zooepidemicus MTCC 3523 to produce HA, the broth was thoroughly purified to separate cell debris and insoluble impurities using a filtration procedure and a variety of adsorbents for soluble impurities. Nucleic acids, proteins with high molecular weight, were successfully removed from the broth using activated carbons and XAD-7 resins. In contrast, insoluble and low molecular weight impurities were removed using diafiltration, with HA recovery of 79.16% and purity close to 90%. Different analytical and characterization procedures such as Fourier transform-infrared spectroscopy, X-ray diffraction, nuclear magnetic resonance, and scanning electron microscopy validated the presence, purity, and structure of HA. Microbial HA showed activity in tests for 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical-scavenging (4.87 ± 0.45 kmol TE/g), total antioxidant capacity (13.32 ± 0.52%), hydroxyl radical-scavenging (32.03 ± 0.12%), and reducing power (24.85 ± 0.45%). The outcomes showed that the precipitation, adsorption, and diafiltration processes are suitable for extracting HA from a fermented broth under the chosen operating conditions. The HA produced was of pharmaceutical grade for non-injectable applications.

Comprehensive review on biosynthesis of hyaluronic acid with different molecular weights and its biomedical applications

Hyaluronic acid (HA), an anionic and nonsulfated glycosaminoglycan, is the main structural component of various tissues and plays an important role in various biological processes. Given the promising properties of HA, such as high cellular compatibility, moisture retention, antiaging, proper interaction with cells, and CD44 targeting, HA can be widely used extensively in drug delivery, tissue engineering, wound healing, and cancer therapy. HA can obtain from animal tissues and microbial fermentation, but its applications depend on its molecular weight. Microbial fermentation is a common method for HA production on an industrial scale and S. zooepidemicus is the most frequently used strain in HA production. Culture conditions including pH, temperature, agitation rate, aeration speed, shear stress, dissolved oxygen, and bioreactor type significantly affect HA biosynthesis properties. In this review all the HA production methods and purification techniques to improve its physicochemical and biological properties for various biomedical applications are discussed in details. In addition, we showed that how HA molecular weight can significantly affect its properties and applications.

Single-molecule AFM study of hyaluronic acid softening in electrolyte solutions

Investigation of hyaluronic acid (HA) morphology and mechanical properties at a single-molecule level is important for the development of HA based biomaterials. We have developed the atomic force microscopy (AFM) based approach for quantitative characterization of conformation of HA molecules. HA molecules adsorbed on a modified graphitic surface form oriented linear segments. Conformation of HA molecules can be considered as two-dimensional quasi-projection of a three-dimensional conformation locally straightened by a substrate. The persistence length and Young's modulus of biomolecules estimated using wormlike chain model decrease from 15.7 to 9.9 nm, and from ∼21 to ∼13 GPa, respectively, when KCl concentration increases from 0 to 100 mM. The dependence of the persistence length on ionic strength supports the Odijk-Skolnick-Fixman model of polyelectrolyte stiffening in electrolyte solution. The obtained results represent a new insight into the conformation and mechanical characteristics of HA molecules and complement the characterization of this biopolymer by bulk methods.

Development of In Situ Product Recovery (ISPR) System Using Amberlite IRA67 for Enhanced Biosynthesis of Hyaluronic Acid by Streptococcus zooepidemicus

High broth viscosity due to the accumulation of hyaluronic acid (HA) causes a limited yield of HA. It is a major problem of HA production using Streptococcus zooepidemicus. Extractive fermentation via in situ product recovery (ISPR) was utilized to enhance the HA production. Resins from Amberlite: IRA400 Cl; IRA900 Cl; IRA410 Cl; IRA402 Cl; and IRA67 were tested for the HA adsorption. IRA67 showed high adsorption capacity on HA. The study of the adsorption via a 2 L stirred tank bioreactor of S. zooepidemicus fermentation was investigated to elucidate the adsorption of HA onto IRA67 in dispersed and integrated internal column systems. The application of a dispersed IRA67 improved the HA production compared to the fermentation without resin addition by 1.37-fold. The HA production was further improved by 1.36-fold with an internal column (3.928 g/L) over that obtained with dispersed IRA67. The cultivation with an internal column shows the highest reduction of viscosity value after the addition of IRA67 resin: from 58.8 to 23.7 (mPa·s), suggesting the most effective ISPR of HA. The improved biosynthesis of HA indicated that an extractive fermentation by ISPR adsorption is effective and may streamline the HA purification.

Natural Biopolymers as Smart Coating Materials of Mesoporous Silica Nanoparticles for Drug Delivery

In recent years, the functionalization of mesoporous silica nanoparticles (MSNs) with different types of responsive pore gatekeepers have shown great potential for the formulation of drug delivery systems (DDS) with minimal premature leakage and site-specific controlled release. New nanotechnological approaches have been developed with the objective of utilizing natural biopolymers as smart materials in drug delivery applications. Natural biopolymers are sensitive to various physicochemical and biological stimuli and are endowed with intrinsic biodegradability, biocompatibility, and low immunogenicity. Their use as biocompatible smart coatings has extensively been investigated in the last few years. This review summarizes the MSNs coating procedures with natural polysaccharides and protein-based biopolymers, focusing on their application as responsive materials to endogenous stimuli. Biopolymer-coated MSNs, which conjugate the nanocarrier features of mesoporous silica with the biocompatibility and controlled delivery provided by natural coatings, have shown promising therapeutic outcomes and the potential to emerge as valuable candidates for the selective treatment of various diseases.

Prospective bacterial and fungal sources of hyaluronic acid: A review

The unique biological and rheological properties make hyaluronic acid a sought-after material for medicine and cosmetology. Due to very high purity requirements for hyaluronic acid in medical applications, the profitability of streptococcal fermentation is reduced. Production of hyaluronic acid by recombinant systems is considered a promising alternative. Variations in combinations of expressed genes and fermentation conditions alter the yield and molecular weight of produced hyaluronic acid. This review is devoted to the current state of hyaluronic acid production by recombinant bacterial and fungal organisms.

Hyaluronic acid production by utilizing agro-industrial waste cane molasses

Hyaluronic acid is a polysaccharide endowed with distinctive biological and physiological competencies. Given its queer properties, hyaluronic acid has exclusive praxis in the cosmetics and medical industries. The surmounting demand for hyaluronic acid is the propulsion behind the necessity for finding the amenable ways for its production. Fermentation progression of Streptococcus zooepidemicus is reckoned as the superlative prompt and ambient approach for hyaluronic acid fabrication. For the unabated advancements in the industrial production of hyaluronan, industrial byproducts utilization is a fateful stile. The recent perusal is to optimize the fermentation production conditions of hyaluronic acid using cane molasses (a byproduct of sugar production) as a carbon source. The impact of different ranges of temperatures (33-41 °C), pH (6-8), and agitation rates (100-250 rpm) on the production process was calibrated using RSM using CCD as a statistical modality. In a 3.7 L bioreactor, 3.31 g/L hyaluronic acid was achieved at 9.74 percent molasses, 36.2 °C, pH 6.46, and a 207 rpm agitation rate using a batch fermentation technique. With a pH of 7, HPLC was conducted at 25 °C using a C18 column at a rate of 0.8 ml/min, and the wavelength was determined using a UV detector. The average retention time was 2.202 min. The FT-IR spectrum's output was also observed, and it matched the standard hyaluronic acid well.

A Concise Review of Extraction and Characterization of Chondroitin Sulphate from Fish and Fish Wastes for Pharmacological Application

Chondroitin sulphate (CS) is one of the most predominant glycosaminoglycans (GAGs) available in the extracellular matrix of tissues. It has many health benefits, including relief from osteoarthritis, antiviral properties, tissue engineering applications, and use in skin care, which have increased its commercial demand in recent years. The quest for CS sources exponentially increased due to several shortcomings of porcine, bovine, and other animal sources. Fish and fish wastes (i.e., fins, scales, skeleton, bone, and cartilage) are suitable sources of CS as they are low cost, easy to handle, and readily available. However, the lack of a standard isolation and characterization technique makes CS production challenging, particularly concerning the yield of pure GAGs. Many studies imply that enzyme-based extraction is more effective than chemical extraction. Critical evaluation of the existing extraction, isolation, and characterization techniques is crucial for establishing an optimized protocol of CS production from fish sources. The current techniques depend on tissue hydrolysis, protein removal, and purification. Therefore, this study critically evaluated and discussed the extraction, isolation, and characterization methods of CS from fish or fish wastes. Biosynthesis and pharmacological applications of CS were also critically reviewed and discussed. Our assessment suggests that CS could be a potential drug candidate; however, clinical studies should be conducted to warrant its effectiveness.

A Review on Current Strategies for Extraction and Purification of Hyaluronic Acid

Since it is known that hyaluronic acid contributes to soft tissue growth, elasticity, and scar reduction, different strategies of producing HA have been explored in order to satisfy the current demand of HA in pharmaceutical products and formulations. The current interest deals with production via bacterial and yeast fermentation and extraction from animal sources; however, the main challenge is the right extraction technique and strategy since the original sources (e.g., fermentation broth) represent a complex system containing a number of components and solutes, which complicates the achievement of high extraction rates and purity. This review sheds light on the main pathways for the production of HA, advantages, and disadvantages, along with the current efforts in extracting and purifying this high-added-value molecule from different sources. Particular emphasis has been placed on specific case studies attempting production and successful recovery. For such works, full details are given together with their relevant outcomes.

Hyaluronic acid production and purification techniques: a review

Hyaluronic acid (HA) is an exopolysaccharide extracted from several sources such as rooster combs, umbilical cords and microorganisms. A system that controls temperature, agitation and aeration of bacterial cultures could make the HA production autonomous. Therefore, HA of microbial origin is set to take over alternative methods of production. Furthermore, the use of different nutrient sources in the culture medium and the purification stage applied in the process can cause physicochemical alterations on the bioproduct. For instance, structural modifications that change the molecular weight of HA may alter its elastic and viscoelastic properties. As a result, HA synthesized by microbes has applications in pharmacology, biotechnology, and tissue engineering. Our aim here, is to show the vast range of applications by compiling articles and patents on the culture media or genetic modifications of microorganisms that synthesize HA.

Comparative Economic Analysis Between Endogenous and Recombinant Production of Hyaluronic Acid

Hyaluronic acid (HA) is a biopolymer with a wide range of applications, mainly in the cosmetic and pharmaceutical sectors. Typical industrial-scale production utilizes organisms that generate HA during their developmental cycle, such as Streptococcus equi sub. zooepidemicus. However, a significant disadvantage of using Streptococcus equi sub. zooepidemicus is that it is a zoonotic pathogen, which use at industrial scale can create several risks. This creates opportunities for heterologous, or recombinant, production of HA. At an industrial scale, the recovery and purification of HA follow a series of precipitation and filtration steps. Current recombinant approaches are developing promising alternatives, although their industrial implementation has yet to be adequately assessed. The present study aims to create a theoretical framework to forecast the advantages and disadvantages of endogenous and recombinant strains in production with the same downstream strategy. The analyses included a selection of the best cost-related recombinant and endogenous production strategies, followed by a sensitivity analysis of different production variables in order to identify the three most critical parameters. Then, all variables were analyzed by varying them simultaneously and employing multiple linear regression. Results indicate that, regardless of HA source, production titer, recovery yield and bioreactor scale are the parameters that affect production costs the most. Current results indicate that recombinant production needs to improve current titer at least 2-fold in order to compete with costs of endogenous production. This study serves as a platform to inform decision-making for future developments and improvements in the recombinant production of HA.

High-Molecular-Weight Hyaluronic Acid Vehicle Can Deliver Gadolinium Into the Cochlea at a Higher Concentration for a Longer Duration: A 9.4-T Magnetic Resonance Imaging Study

Intratympanic (IT) gadolinium (Gd) injection is one method of delivering Gd into the inner ear to evaluate the amount of endolymphatic hydrops (EH) using magnetic resonance imaging (MRI). As Gd is usually prepared in a fluid form mixed with saline, Gd injected into the middle ear drains easily through the Eustachian tube within several hours. High-molecular-weight (hMW) hyaluronic acid (HA) is an ideal vehicle for IT Gd due to its viscous and adhesive properties. The present study was performed to elucidate whether novel hMW HA is superior to conventional HA in delivering Gd into the inner ear in the short term. The second aim was to verify the long-term Gd delivery efficiency of hMW HA compared to the standard-of-care vehicle (saline). IT Gd injection and 3D T1-weighted MRI were performed in 13 rats. For the short-term study (imaging after 1, 2, and 3 h), the left ear was treated with hMW HA+Gd and the right ear with conventional HA+Gd. For the long-term study (imaging after 1, 2, 3, and 4 h, 1 – 3 days, and 7 – 10 days), the left ear was treated with hMW HA+Gd and the right ear with saline+Gd. Signal intensities (SIs) in the scala tympani (ST) and scala vestibuli (SV) were quantified. Compared to conventional HA, signal enhancement was 2.3 – 2.4 times greater in the apical and middle turns after hMW HA+Gd injection (SV at 1 h). In comparison to the standard-of-care procedure, the SI was not only greater in the short term but the higher SI also lasted for a longer duration. On days 7 – 10 after IT Gd delivery, the SI in the basal turn was 1.9 – 2.1 times greater in hMW HA+Gd-treated ears than in saline IT Gd-treated ears. Overall, hMW HA may be a useful vehicle for more efficient IT Gd delivery. Gd enhancement in the cochlea improved approximately two-fold when hMW HA was used. In addition, this greater enhancement lasted for up to 7 – 10 days. Repeated MRI of EH may be possible for several days with a single IT hMW HA+Gd delivery.

Self-crosslinkable hyaluronate-based hydrogels as a soft tissue filler

With increasing interest in aging and skin care, the use of fillers to increase the volume of soft tissue volume is increasing globally. However, the side effects caused by the residual chemical crosslinking agents present in these fillers limit the effective application of commercialized filler products. Therefore, the development of a novel crosslinking system with a non-toxic chemical crosslinking agent is required to overcome the limitations of commercial hyaluronate (HA)-based fillers. In this paper, a new injectable hydrogel with enhanced mechanical properties, tissue adhesion, injectability, and biocompatibility is reported. The HA derivatives modified with catechol groups (HA-DA) were crosslinked by self-oxidation under in vivo physiological conditions (pH 7.4) without chemical crosslinkers to form hydrogels, which can be further accelerated by the dissolved oxygen in the body. The fabricated HA-DA filler showed excellent mechanical properties and could be easily injected with a low injection force. Further, the HA-DA filler stably attached to the injection site due to the tissue adhesion properties of the catechol groups, thus leading to an improved displacement stability. In addition, the HA-DA filler showed excellent cell viability, cell proliferation, and biocompatibility. Therefore, the HA-DA hydrogel is a novel soft tissue filler with great potential to overcome the limitations of commercial soft tissue fillers.

Stable oxime-crosslinked hyaluronan-based hydrogel as a biomimetic vitreous substitute

Vitreous substitutes are clinically used to maintain retinal apposition and preserve retinal function; yet the most used substitutes are gases and oils which have disadvantages including strict face-down positioning post-surgery and the need for subsequent surgical removal, respectively. We have engineered a vitreous substitute comprised of a novel hyaluronan-oxime crosslinked hydrogel. Hyaluronan, which is naturally abundant in the vitreous of the eye, is chemically modified to crosslink with poly(ethylene glycol)-tetraoxyamine via oxime chemistry to produce a vitreous substitute that has similar physical properties to the native vitreous including refractive index, density and transparency. The oxime hydrogel is cytocompatible in vitro with photoreceptors from mouse retinal explants and biocompatible in rabbit eyes as determined by histology of the inner nuclear layer and photoreceptors in the outer nuclear layer. The ocular pressure in the rabbit eyes was consistent over 56 d, demonstrating limited to no swelling. Our vitreous substitute was stable in vivo over 28 d after which it began to degrade, with approximately 50% loss by day 56. We confirmed that the implanted hydrogel did not impact retina function using electroretinography over 90 days versus eyes injected with balanced saline solution. This new oxime hydrogel provides a significant improvement over the status quo as a vitreous substitute.

Preparation, purification, and characterization of low-molecular-weight hyaluronic acid

OBJECTIVE

The use and commercial value of hyaluronic acid (HA) as an important element in the pharmaceutical, biomedical, and cosmetics industry is because of its purity. Four recombinant strains of Corynebacterium glutamicum containing different genes were used to produce HA.

RESULTS

The production parameters were measured and strain 183.2, with the highest amount of HA (2.15 mg/ml), was selected for further experiments. HA was precipitated by different ratios of ethanol-isopropanol at 4 °C and - 20 °C. Active charcoal (1%) was added to the solvent precipitation mixture at pH 5 and 10. Finally, to achieve more purity and separation, gel filtration chromatography was used. The best result was obtained using an ethanol-isopropanol ratio of 1:1 of at - 20 °C, followed by active charcoal treatment at the acidic pH, and three fractions of the chromatography with molecular weights of 27, 27-110, and < 27 KDa were more analyzed with electrophoresis and FTIR.

CONCLUSIONS

The present study described a simple, economical, and reproducible method resulting in a high yield for low-MW HA from C. glutamicum.

Hyaluronic acid and Chondroitin sulfate from marine and terrestrial sources: Extraction and purification methods

Hyaluronic acid (HA) and chondroitin sulfate (CS) are valuable bioactive polysaccharides that have been highly used in biomedical and pharmaceutical applications. Extensive research was done to ensure their efficient extraction from marine and terrestrial by-products at a high yield and purity, using specific techniques to isolate and purify them. In general, the cartilage is the most common source for CS, while the vitreous humor is main used source of HA. The developed methods were based in general on tissue hydrolysis, removal of proteins and purification of the target biopolymers. They differ in the extraction conditions, enzymes and/or solvents used and the purification technique. This leads to specific purity, molecular weight and sulfation pattern of the isolated HA and CS. This review focuses on the analysis and comparison of different extraction and purification methods developed to isolate these valuable biopolymers from marine and terrestrial animal by-products.

Bacterial biopolymers: from pathogenesis to advanced materials

Bacteria are prime cell factories that can efficiently convert carbon and nitrogen sources into a large diversity of intracellular and extracellular biopolymers, such as polysaccharides, polyamides, polyesters, polyphosphates, extracellular DNA and proteinaceous components. Bacterial polymers have important roles in pathogenicity, and their varied chemical and material properties make them suitable for medical and industrial applications. The same biopolymers when produced by pathogenic bacteria function as major virulence factors, whereas when they are produced by non-pathogenic bacteria, they become food ingredients or biomaterials. Interdisciplinary research has shed light on the molecular mechanisms of bacterial polymer synthesis, identified new targets for antibacterial drugs and informed synthetic biology approaches to design and manufacture innovative materials. This Review summarizes the role of bacterial polymers in pathogenesis, their synthesis and their material properties as well as approaches to design cell factories for production of tailor-made bio-based materials suitable for high-value applications.

Effect of photoinitiator on chain degradation of hyaluronic acid

OBJECTIVES

Photocrosslinking systems of polymers have been widely studied using UV or visible light irradiation. However, the photodegradation behavior derived from light irradiation was rarely reported, comparing with the photocrosslinking. In this study, the tyramine-modified hyaluronic acid (HA/Tyr) hydrogel was prepared using riboflavin (RF) as a photoinitiator, and the degradation behavior of HA by the reactive oxygen species (ROS) generated in photochemical process was investigated.

MATERIALS AND METHODS

The HA/Tyr conjugate was synthesized by EDC/NHS chemistry to introduce phenol group. Degree of substitution (DS, %) of phenol group to HA molecule was about 25%. The structural change of HA/Tyr was measured by proton nuclear magnetic resonance (1H-NMR) and attenuated total reflectance infrared spectroscopy (ATR-FTIR), and the rheological properties of photocrosslinked HA/Tyr hydrogel were investigated by rheometer.

RESULTS

The HA/Tyr solution with 25% substitution formed a stable hydrogel via visible light irradiation in the presence of RF photoinitiator. Rheological data of HA/Tyr solution showed that the storage modulus (G') was increased with increasing HA concentration. Additionally, it was found that RF initiated by visible light irradiation induced the degradation of HA molecular chain, and consequently reduced the viscosity of HA/Tyr solutions.

CONCLUSION

The results indicate that RF-based photoinitiator system caused the degradation of HA molecule by ROS generated in photochemical process as well as the crosslinking of HA/Tyr.

Preparation and investigation of hydrolyzed polyacrylonitrile as a preliminary biomedical hydrogel

BACKGROUND

Hydrolyzed polyacrylonitrile (HPAN) has attracted much attention as a hydrogel for a broad range of biomedical applications. Therefore, in this study, we prepared HPAN derivatives with controllable compositions by the radical polymerization of acrylonitrile (AN), methacrylic acid (MAA) and N-isopropylacrylamide (NIPAM) monomers.

RESULTS

The prepared poly(AN-co-MAA-co-NIPAM) copolymers had different ratios of AN, MAA, and NIPAM and molecular weights ranging from 2000 to 50,000. The copolymers were prepared as films to examine their properties. The prepared copolymer films showed different solubilities, contact angles, and swelling ratios. The properties of the copolymer films were affected by the hydrophobic PAN segments and the hydrophilic PMAA or PNIPAM segments.

CONCLUSION

Thus, we conclude that introducing PMAA and PNIPAM segments with different ratios and lengths into PAN segments could represent a method of controlling the hydrogel properties of copolymers.