Thermal and in vitro degradation properties of the NH2-containing PHBV films

Thermal and physicochemical dissimilarities of biological poly-3-hydroxyalkanoates following graft copolymerization with acrylamide under ultrasonication

Poly-3-hydroxyalkanoate (PHA) and polyacrylamide (PAM) are potentially copolymerized into a novel hybrid material with distinctive characteristics but scarcely explored. In this study, the copolymerization of semicrystalline and amorphous forms of PHA, designated as scPHA and amPHA, with PAM utilizing ultrasonication and hydrogen peroxide as the initiator under defined conditions were investigated. The effect of varying acrylamide amounts on the yield and properties of graft copolymers (PHA-g-MA) were characterized by molecular weight changes, thermal and spectroscopic properties. Grafting scPHA and amPHA with PAM influenced their initial molecular weights (Mw). Specifically, scPHA's Mw decreased from 140 × 103 to ∼130 × 103 g mol-1, while amPHA's Mw increased from 62 × 103 to ∼68 × 103 g mol-1. Additionally, scPHA and amPHA copolymers showed an increase in thermal decomposition temperature (Td) from 240 °C to 265 °C and 275 °C to 285 °C, respectively. The presence of an amide functional group in the copolymers was authenticated by a Raman peak at 1100 cm-1. Both scPHA and amPHA graft copolymers exhibited unique contrast to their neat counterpart. The scPHA-g-PAMs showed strong crystalline characteristics, evidenced by elevated glass transition and melting temperatures, alterations in crystalline planes and surface morphologies, and a decrease in dielectric constant values. Conversely, amPHA-g-PAMs showed pronounced amorphous characteristics, substantiated by a lowered glass transition and melting temperatures, altered surface morphologies, and increased dielectric constant values. The observations made are attributed to distinct chain packing characteristics between both graft copolymers, which are the consequence of the PHA alkyl side chains length. The biological PHA graft copolymers may offer a diverse array of applications such composite for tissue engineering and biosensor development.

Enhancing the Potential of PHAs in Tissue Engineering Applications: A Review of Chemical Modification Methods

Polyhydroxyalkanoates (PHAs) are a family of polyesters produced by many microbial species. These naturally occurring polymers are widely used in tissue engineering because of their in vivo degradability and excellent biocompatibility. The best studied among them is poly(3-hydroxybutyrate) (PHB) and its copolymer with 3-hydroxyvaleric acid (PHBV). Despite their superior properties, PHB and PHBV suffer from high crystallinity, poor mechanical properties, a slow resorption rate, and inherent hydrophobicity. Not only are PHB and PHBV hydrophobic, but almost all members of the PHA family struggle because of this characteristic. One can overcome the limitations of microbial polyesters by modifying their bulk or surface chemical composition. Therefore, researchers have put much effort into developing methods for the chemical modification of PHAs. This paper explores a rarely addressed topic in review articles-chemical methods for modifying the structure of PHB and PHBV to enhance their suitability as biomaterials for tissue engineering applications. Different chemical strategies for improving the wettability and mechanical properties of PHA scaffolds are discussed in this review. The properties of PHAs that are important for their applications in tissue engineering are also discussed.

Functionalization of graphene oxide with amphiphilic block copolymer to enhance antibacterial activity

Functionalization of GO with an amphiphilic block copolymer is designed with an aim to enhance its biocompatibility, however, long copolymer chains can screen the blade effect of GO to sacrifice its antimicrobial activities. To solve this problem, low molecular weight of poly(ethylene glycol) (PEG), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and their block copolymer were respectively introduced onto GO via an isophorone diisocyanate modified GO as a intermediate, followed by a solvent evaporation of an oil-in-water emulsion treatment (SE treatment) to induce block copolymer into polymer micelle via phase separation to refresh the sharp edges of GO. Block copolymer modified GO possessed similar dispersibility and stability to PEG modified GO, and even higher loading capacity of the hydrophobic drug than PHBV modified GO, illustrating its superior properties to homopolymer. PEG, PHBV and their block copolymer modified GO were nontoxic towards ATDC5 cells while cultured for 3 days and compatible with erythrocytes within 8 h. SE treatment enhanced greatly the loading capacity of the hydrophobic drug and the accumulative release reached 91.3% within 24 h. The inhibition zone of the block copolymer modified GO was 14.1 mm and 14.8 mm against E. coli and S. aureus, comparable to that of PEG modified GO. The bacterial reduction rate of the copolymer micelle modified GO was 87.1% and 82.7% towards E. coli and S. aureus, much greater than that of PEG, PHBV and their block copolymer modified GO at a concentration of 1 mg/mL. The antibiofilm capacity of the copolymer micelle modified GO were equal to that of PEG modified, demonstrating its great promise in tissue engineering application for repair of infected tissue defects.

A Review of Bioresorbable Implantable Medical Devices: Materials, Fabrication, and Implementation

Implantable medical devices (IMDs) are designed to sense specific parameters or stimulate organs and have been actively used for treatment and diagnosis of various diseases. IMDs are used for long-term disease screening or treatments and cannot be considered for short-term applications since patients need to go through a surgery for retrieval of the IMD. Advances in bioresorbable materials has led to the development of transient IMDs that can be resorbed by bodily fluids and disappear after a certain period. These devices are designed to be implanted in the adjacent of the targeted tissue for predetermined times with the aim of measurement of pressure, strain, or temperature, while the bioelectronic devices stimulate certain tissues. They enable opportunities for monitoring and treatment of acute diseases. To realize such transient and miniaturized devices, researchers utilize a variety of materials, novel fabrication methods, and device design strategies. This review discusses potential bioresorbable materials for each component in an IMD followed by programmable degradation and safety standards. Then, common fabrication methods for bioresorbable materials are introduced, along with challenges. The final section provides representative examples of bioresorbable IMDs for various applications with an emphasis on materials, device functionality, and fabrication methods.

Electrospun Active Biopapers of Food Waste Derived Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with Short-Term and Long-Term Antimicrobial Performance

This research reports about the development by electrospinning of fiber-based films made of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) derived from fermented fruit waste, so-called bio-papers, with enhanced antimicrobial performance. To this end, different combinations of oregano essential oil (OEO) and zinc oxide nanoparticles (ZnONPs) were added to PHBV solutions and electrospun into mats that were, thereafter, converted into homogeneous and continuous films of ~130 μm. The morphology, optical, thermal, mechanical properties, crystallinity, and migration into food simulants of the resultant PHBV-based bio-papers were evaluated and their antimicrobial properties were assessed against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in both open and closed systems. It was observed that the antimicrobial activity decreased after 15 days due to the release of the volatile compounds, whereas the bio-papers filled with ZnONPs showed high antimicrobial activity for up to 48 days. The electrospun PHBV biopapers containing 2.5 wt% OEO + 2.25 wt% ZnONPs successfully provided the most optimal activity for short and long periods against both bacteria.

Crystallization and mechanical properties of reinforced PHBV composites using melt compounding: Effect of CNCs and CNFs

Nanocellulose reinforced poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) composites were prepared using melt compounding. The effects of nanocellulose types (CNCs and CNFs) and nanocellulose content (1, 2, 3, 4, 5, 6 and 7wt%) on the crystallization, thermal and mechanical properties of PHBV composites were systematically compared in this study. The thermal stability of PHBV composites was improved by both CNCs and CNFs. CNFs with a higher thermal stability leaded to a higher thermal stability of PHBV composites. Both CNCs and CNFs induced a reduction in the crystalline size of PHBV spherulites. Furthermore, CNCs could act as a better nucleating agent for PHBV than did CNFs. CNCs and CNFs showed reinforcing effects in PHBV composites. At the equivalent content of nanocellulose, CNCs led to a higher tensile modulus of PHBV composites than did CNFs. 1wt% CNCs/PHBV composites exhibited the most optimum mechanical properties.

Effect of different solvent systems on PHBV/PEO electrospun fibers

The selection of non-hazardous solvent systems is an important factor that can significantly influence fiber formation during polymer electrospinning.