Characterization of Oligomeric Hydroxyalkanoic Acids from Thermal Decomposition of Palm Kernel Oil–Based Biopolyester

Phytotherapeutic Hierarchical PCL-Based Scaffolds as a Multifunctional Wound Dressing: Combining 3D Printing and Electrospinning

This study focuses on developing hybrid scaffolds incorporating phytotherapeutic agents via a combination of three-dimensional (3D) printing and electrospinning to enhance mechanical properties and provide antibacterial activity, in order to address the limitations of traditional antibiotics. In this regard, 3D-printed polycaprolactone (PCL) struts are first fabricated using fused deposition modeling (FDM). Then, alkaline surface treatment is applied to improve the adhesion of electrospun nanofibers. Finally, peppermint oil (PEP) or clove oil (CLV)-incorporated PCL-gelatin (GEL) electrospun nanofibers are collected on top of the 3D-printed PCL scaffolds by electrospinning. Incorporating PEP or CLV into PCL-GEL electrospun nanofibers enhances the scaffold's layer detachment and adhesion force. In addition, the DPPH free radical scavenging activity assay indicates that incorporating PEP or CLV improves the antioxidant properties of the scaffolds. Further, antibacterial activity results reveal that PEP or CLV incorporated scaffolds exhibit inhibition against Staphylococcus aureus and Escherichia coli bacteria. Moreover, anti-inflammatory assays show that scaffolds reduce the concentration of nitric oxide (NO) released from Raw 264.7 macrophage-like cells. On the other hand, the phytotherapeutic hierarchical scaffolds have no toxic effect on normal human dermal fibroblast (NHDF) cells, and PEP or CLV enhance cell attachment and proliferation. Overall, incorporating natural phytotherapeutic agents into hierarchical scaffolds shows promise for advancing wound healing applications.

Microbial degradation of linseed oil-based elastomer and subsequent accumulation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer

The microbial synthesis of environment-friendly poly(3-hydroxybutyrate--co-3-hydroxyvalerate), PHBV, has been performed by using an alkaliphilic microorganism, Alkaliphilus oremlandii OhILAs strain (GenBank Accession number NR_043674.1), at pH 8 and at a temperature of 30-32 °C through the biodegradation of linseed oil-based elastomer. The yield of the copolymer on dry cell weight basis is 90 %. The elastomers used for the biodegradation have been synthesized by cationic polymerization technique. The yield of the PHBV copolymer also varies with the variation of linseed oil content (30-60 %) in the elastomer. Spectroscopic characterization ((1)H NMR and FTIR) of the accumulated product through biodegradation of linseed oil-based elastomers indicates that the accumulated product is a PHBV copolymer consisting of 13.85 mol% of 3-hydroxyvalerate unit. The differential scanning calorimetry (DSC) results indicate a decrease in the melting (T m) and glass transition temperature (T g) of PHBV copolymer with an increase in the content of linseed oil in the elastomer, which is used for the biodegradation. The gel permeation chromatography (GPC) results indicate that the weight average molecular weight (M w) of PHBV copolymer decreases with an increasing concentration of linseed oil in the elastomer. The surface morphology of the elastomer before and after biodegradation is observed under scanning electron microscope (SEM) and atomic force microscope (AFM); these results indicate about porous morphology of the biodegraded elastomer.

Viscoelastic, Spectroscopic, and Microscopic Characterization of Novel Bio-Based Plasticized Poly(vinyl chloride) Compound

Plasticized poly(vinyl chloride) (PVC) is one of the most widely consumed commodity plastics. Nevertheless, the commonly used plasticizers, particularly phthalates, are found to be detrimental to the environment and human health. This study aimed to investigate the ability of an alternative greener material, medium-chain-length polyhydroxyalkanoates (mcl-PHA), a kind of biopolyester and its thermally degraded oligoesters, to act as a compatible bioplasticizer for PVC. In this study, mcl-PHA were synthesized byPseudomonas putidaPGA1 in shake flask fermentation using saponified palm kernel oil (SPKO) and subsequently moderately thermodegraded to low molecular weight oligoesters (degPHA). SEM, ATR-FTIR,1H-NMR, and DMA were conducted to study the film morphology, microstructure, miscibility, and viscoelastic properties of the PVC-PHA and PVC/degPHA binary blends. Increased height and sharpness of tanδmax⁡peak for all binary blends reveal an increase in chain mobility in the PVC matrix and high miscibility within the system. The PVC-PHA miscibility is possibly due to the presence of specific interactions between chlorines of PVC with the C=O group of PHA as evidenced by spectroscopic analyses. Dynamic viscoelastic measurements also showed that mcl-PHA and their oligoesters could reduce theTgof PVC, imparting elasticity to the PVC compounds and decreasing the stiffness of PVC.

Lipase catalyzed ultrasonic synthesis of poly-4-hydroxybutyrate-co-6-hydroxyhexanoate

Four different lipases were compared for ultrasound-mediated synthesis of the biodegradable copolymer poly-4-hydroxybutyrate-co-6-hydroxyhexanoate. The copolymerization was carried out in chloroform. Of the enzymes tested, Novozym 435 exhibited the highest copolymerization rate, in fact the reaction rate was observed to increase with about 26-fold from 30 to 50°C (7.9×10(-3)Ms(-1)), sonic power intensity of 2.6×10(3)Wm(-2) and dissipated energy of 130.4Jml(-1). Copolymerization rates with the Candida antarctica lipase A, Candida rugosa lipase, and Lecitase Ultra™ were lower at 2.4×10(-4), 1.3×10(-4) and 3.5×10(-4)Ms(-1), respectively. The catalytic efficiency depended on the enzyme. The efficiency ranged from 4.15×10(-3)s(-1)M(-1) for Novozym 435-1.48×10(-3)s(-1)M(-1) for C. rugosa lipase. Depending on the enzyme and sonication intensity, the monomer conversion ranged from 8.2% to 48.5%. The sonication power, time and temperature were found to affect the rate of copolymerization. Increasing sonication power intensity from 1.9×10(3) to 4.5×10(3)Wm(-2) resulted in an increased in acoustic pressure (P(a)) from 3.7×10(8) to 5.7×10(8)Nm(-2) almost 2.4-3.7 times greater than the acoustic pressure (1.5×10(8)Nm(-2)) that is required to cause cavitation in water. A corresponding acoustic particle acceleration (a) of 9.6×10(3)-1.5×10(4)ms(-2) was calculated i.e. approximately 984-1500 times greater than under the action of gravity.