Recent Development of Polyhydroxyalkanoates (PHA)-Based Materials for Antibacterial Applications: A Review

Monodisperse polyhydroxyalkanoate nanoparticles as self-sticky and bio-resorbable tissue adhesives

Monodisperse nanoparticles of biodegradable polyhydroxyalkanoates (PHAs) polymers, copolymers of 3-hydroxybutyrate (3HB) and 4-hydroxybutyrate (4HB), are synthesized using a membrane-assisted emulsion encapsulation and evaporation process for biomedical resorbable adhesives. The precise control over the diameter of these PHA particles, ranging from 100 nm to 8 μm, is achieved by adjusting the diameter of emulsion or the PHA concentration. Mechanical properties of the particles can be tailored based on the 3HB to 4HB ratio and molecular weight, primarily influenced by the level of crystallinity. These monodisperse PHA particles in solution serve as adhesives for hydrogel systems, specifically those based on poly(N, N-dimethylacrylamide) (PDMA). Semi-crystalline PHA nanoparticles exhibit stronger adhesion energy than their amorphous counterparts. Due to their self-adhesiveness, adhesion energy increases even when those PHA nanoparticles form multilayers between hydrogels. Furthermore, as they degrade and are resorbed into the body, the PHA nanoparticles demonstrate efficacy in in vivo wound closure, underscoring their considerable impact on biomedical applications.

Characterization of Electrospinning Chitosan Nanofibers Used for Wound Dressing

Wound dressings play a crucial role in promoting wound healing by providing a protective barrier against infections and facilitating tissue regeneration. Electrospun nanofibers have emerged as promising materials for wound dressing applications due to their high surface area, porosity, and resemblance to the extracellular matrix. In this study, chitosan, a biocompatible and biodegradable polymer, was electrospun into nanofibers for potential use in wound dressing. The chitosan nanofibers were characterized by using various analytical techniques to assess their morphology and biocompatibility. Scanning electron microscopy (SEM) revealed the formation of uniform and bead-free nanofibers with diameters ranging from tens to hundreds of nanometers. Structural analysis, including Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD), elucidated the chemical composition and crystalline structure of the nanofibers. Furthermore, in vitro studies evaluated the cytocompatibility of the chitosan nanofibers with human dermal fibroblasts, demonstrating cell viability and proliferation on the nanofibers. Additionally, antibacterial properties were assessed to evaluate the potential of chitosan nanofibers in preventing wound infections. Overall, the characterization results highlight the promising attributes of electrospun chitosan nanofibers as wound dressings, paving the way for further investigation and development in the field of advanced wound care. This study has been carried out for the first time in our region and has assessed the antibacterial properties of electrospun chitosan nanofiber material. The created mat has shown efficaciousness against bacteria that are both gram-positive and gram-negative.

Biogenic Palladium Improved Perchlorate Reduction during Nitrate Co-Reduction by Diverting Electron Flow in a Hydrogenotrophic Biofilm

Microbial reduction of perchlorate (ClO4-) is emerging as a cost-effective strategy for groundwater remediation. However, the effectiveness of perchlorate reduction can be suppressed by the common co-contamination of nitrate (NO3-). We propose a means to overcome the limitation of ClO4- reduction: depositing palladium nanoparticles (Pd0NPs) within the matrix of a hydrogenotrophic biofilm. Two H2-based membrane biofilm reactors (MBfRs) were operated in parallel in long-term continuous and batch modes: one system had only a biofilm (bio-MBfR), while the other incorporated biogenic Pd0NPs in the biofilm matrix (bioPd-MBfR). For long-term co-reduction, bioPd-MBfR had a distinct advantage of oxyanion reduction fluxes, and it particularly alleviated the competitive advantage of NO3- reduction over ClO4- reduction. Batch tests also demonstrated that bioPd-MBfR gave more rapid reduction rates for ClO4- and ClO3- compared to those of bio-MBfR. Both biofilm communities were dominated by bacteria known to be perchlorate and nitrate reducers. Functional-gene abundances reflecting the intracellular electron flow from H2 to NADH to the reductases were supplanted by extracellular electron flow with the addition of Pd0NPs.

Sporadic regional re-emergent cholera: a 19th century problem in the 21st century

Cholera, caused by Vibrio cholerae, is a severe diarrheal disease that necessitates prompt diagnosis and effective treatment. This review comprehensively examines various diagnostic methods, from traditional microscopy and culture to advanced nucleic acid testing like polymerase spiral reaction and rapid diagnostic tests, highlighting their advantages and limitations. Additionally, we explore evolving treatment strategies, with a focus on the challenges posed by antibiotic resistance due to the activation of the SOS response pathway in V. cholerae. We discuss promising alternative treatments, including low-pressure plasma sterilization, bacteriophages, and selenium nanoparticles. The paper emphasizes the importance of multidisciplinary approaches combining novel diagnostics and treatments in managing and preventing cholera, a persistent global health challenge. The current re-emergent 7th pandemic of cholera commenced in 1961 and shows no signs of abeyance. This is probably due to the changing genetic profile of V. cholerae concerning bacterial pathogenic toxins. Given this factor, we argue that the disease is effectively re-emergent, particularly in Eastern Mediterranean countries such as Lebanon, Syria, etc. This review considers the history of the current pandemic, the genetics of the causal agent, and current treatment regimes. In conclusion, cholera remains a significant global health challenge that requires prompt diagnosis and effective treatment. Understanding the history, genetics, and current treatments is crucial in effectively addressing this persistent and re-emergent disease.

Enhancing Targeted Therapy in Hepatocellular Carcinoma through a pH-Responsive Delivery System: Folic Acid-Modified Polydopamine-Paclitaxel-Loaded Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Nanoparticles

Currently, there is an inherent contradiction between the multifunctionality and excellent biocompatibility of anticancer drug nanocarriers, which limits their application. Therefore, to overcome this limitation, we aimed to develop a biocompatible drug delivery system for the treatment of hepatocellular carcinoma (HCC). In this study, we employed poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as the fundamental framework of the nanocarrier and utilized the emulsion solvent evaporation method to fabricate nanoparticles loaded with paclitaxel (PTX), known as PTX-PHBV NPs. To enhance the tumor-targeting capability, a dopamine self-polymerization strategy was employed to form a pH-sensitive coating on the surface of the nanoparticles. Then, folic acid (FA)-targeting HCC was conjugated to the nanoparticles with a polydopamine (PDA) coating by using the Michael addition reaction, resulting in the formation of HCC-targeted nanoparticles (PTX-PHBV@PDA-FA NPs). The PTX-PHBV@PDA-FA NPs were characterized and analyzed by using dynamic light scattering, scanning electron microscopy, fourier-transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. Encouragingly, PTX-PHBV@PDA-FA NPs exhibited remarkable anticancer efficacy in an HCC xenograft mouse model. Furthermore, compared to raw PTX, PTX-PHBV@PDA-FA NPs showed less toxicity in vivo. In conclusion, these results demonstrate the potential of PTX-PHBV@PDA-FA NPs for HCC treatment and biocompatibility.

In Vitro Antioxidant Activity of Green-Synthesized Zinc Oxide (ZnO) Nanoparticles Utilizing Extracts From Allium sativum

INTRODUCTION

The primary objective of this study was to develop an environmentally friendly and efficient method for synthesizing zinc oxide (ZnO) nanoparticles (NPs), utilizing extracts from Allium sativum (garlic) plants, characterizing the synthesized ZnO NPs using various analytical techniques, and assessing their antibacterial and antioxidant properties.

MATERIALS AND METHODS

The synthesis process involved utilizing extracts from garlic plants to create ZnO NPs. The NPs were subjected to comprehensive characterization through UV-visible (UV-vis) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Antibacterial properties were assessed against different microbial strains. In vitro antioxidant properties were evaluated through 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assays. Bioactive compounds in the synthesized NPs were also identified.

RESULTS

Analysis of the UV-vis spectrum confirmed the synthesis of ZnO NPs with an approximate size of 280 nm, as indicated by the absorption peak in the surface plasmon resonance band. FTIR spectroscopy revealed the presence of functional groups such as hydroxyl and carboxyl groups. SEM analysis determined the dimensions of the NPs to be around 11 nm. XRD patterns exhibited distinct Bragg reflections, confirming specific crystallographic planes. In vitro antioxidant assays demonstrated a reduction in absorbance at 517 nm and 734 nm, indicating antioxidant activity. Antibacterial testing revealed inhibition zones against Escherichia coli, Staphylococcus aureus, Streptococcus mutans,and Enterococcus faecalis.

CONCLUSION

The study successfully synthesized ZnO NPs using an eco-friendly method with garlic plant extracts. Characterization techniques confirmed the structural and chemical properties of the NPs. The synthesized NPs exhibited antioxidant and antibacterial activities, showcasing their potential for various applications. The identification of bioactive compounds further contributes to the understanding of the biological properties of the synthesized NPs.

Conformational characteristics of poly(3-hydroxyvalerate) (P3HV) and structure-property relationships of P3HV and poly(3-hydroxybutyrate)

Conformational analysis of biosynthetic and biodegradable poly(3-hydroxyvalerate) (P3HV), an analog of poly(3-hydroxybutyrate) (P3HB), was performed. The only structural difference between the two polymers consists in the side chain, which is either methyl (P3HB) or ethyl (P3HV). Molecular orbital calculations and NMR experiments were conducted on a monomeric model compound to determine the bond conformations of the main and side chains of P3HV. The refined rotational isomeric state (RIS) scheme was applied to derive configurational properties of P3HV. The characteristic ratio of P3HV (2.1-3.0) is smaller than that of P3HB (5.4-5.6), indicating greater conformational flexibility of the P3HV chain. The increased flexibility due to the internal rotation of the ethyl side group of P3HV results in a lower equilibrium melting point (130 °C) compared with P3HB (203 °C). The RIS calculations on P3HV also suggested its potential for rubber-like properties. Periodic density functional theory calculations were used to optimize the crystal structures of P3HB and P3HV and obtain their elastic moduli. Three-dimensional Young's modulus distributions of both crystals are closer to isotropic than anisotropic. In conclusion, the material design and usage of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) are discussed.

Characteristics of Microparticles Based on Resorbable Polyhydroxyalkanoates Loaded with Antibacterial and Cytostatic Drugs

The development of controlled drug delivery systems, in the form of microparticles, is an important area of experimental pharmacology. The success of the design and the quality of the obtained microparticles are determined by the method of manufacture and the properties of the material used as a carrier. The goal is to obtain and characterize microparticles depending on their method of preparation, the chemical composition of the polymer and the load of the drugs. To obtain microparticles, four types of degradable PHAs, differing in their chemical compositions, degrees of crystallinity, molecular weights and temperature characteristics, were used (poly-3-hydroxybutyrate and copolymers 3-hydroxybutyric-co-3-hydroxyvaleric acid, 3-hydroxybutyric-co-4-hydroxybutyric acid, and 3-hydroxybutyric-co-3-hydroxyhexanoic acid). The characteristics of microparticles from PHAs were studied. Good-quality particles with an average particle diameter from 0.8 to 65.0 μm, having satisfactory ζ potential values (from -18 to -50 mV), were obtained. The drug loading content, encapsulation efficiency and in vitro release were characterized. Composite microparticles based on PHAs with additives of polyethylene glycol and polylactide-co-glycolide, and loaded with ceftriaxone and 5-fluorouracil, showed antibacterial and antitumor effects in E. coli and HeLa cultures. The results indicate the high potential of PHAs for the design of modern and efficient drug delivery systems.