MyMedR

Displaying all 6 publications

Abstract:

Sort:

Fulltext Emerging Applications of Versatile Polyaniline-Based Polymers in the Food Industry

Chia MR, Phang SW, Ahmad I

Polymers (Basel), 2022 Nov 28;14(23).
PMID: 36501566 DOI: 10.3390/polym14235168

Intrinsically conducting polymers (ICPs) have been widely studied in various applications, such as sensors, tissue engineering, drug delivery, and semiconductors. Specifically, polyaniline (PANI) stands out in food industry applications due to its advantageous reversible redox properties, electrical conductivity, and simple modification. The rising concerns about food safety and security have encouraged the development of PANI as an antioxidant, antimicrobial agent, food freshness indicator, and electronic nose. At the same time, it plays an important role in food safety control to ensure the quality of food. This study reviews the emerging applications of PANI in the food industry. It has been found that the versatile applications of PANI allow the advancement of modern active and intelligent food packaging and better food quality monitoring systems.
Crazing Effect on the Bio-Based Conducting Polymer Film

Wong PY, Takeno A, Takahashi S, Phang SW, Baharum A

Polymers (Basel), 2021 Oct 06;13(19).
PMID: 34641240 DOI: 10.3390/polym13193425

The biodegradability problem of polymer waste is one of the fatal pollutFions to the environment. Enzymes play an essential role in increasing the biodegradability of polymers. In a previous study, antistatic polymer film based on poly(lactic acid) (PLA) as a matrix and polyaniline (PAni) as a conductive filler, was prepared. To solve the problem of polymer wastes pollution, a crazing technique was applied to the prepared polymer film (PLA/PAni) to enhance the action of enzymes in the biodegradation of polymer. This research studied the biodegradation test based on crazed and non-crazed PLA/PAni films by enzymes. The presence of crazes in PLA/PAni film was evaluated using an optical microscope and scanning electron microscopy (SEM). The optical microscope displayed the crazed in the lamellae form, while the SEM image revealed microcracks in the fibrils form. Meanwhile, the tensile strength of the crazed PLA/PAni film was recorded as 19.25 MPa, which is almost comparable to the original PLA/PAni film with a tensile strength of 20.02 MPa. However, the Young modulus decreased progressively from 1113 MPa for PLA/PAni to 651 MPa for crazed PLA/PAni film, while the tensile strain increased 150% after crazing. The significant decrement in the Young modulus and increment in the tensile strain was due to the craze propagation. The entanglement was reduced and the chain mobility along the polymer chain increased, thus leading to lower resistance to deformation of the polymer chain and becoming more flexible. The presence of crazes in PLA/PAni film showed a substantial change in weight loss with increasing the time of degradation. The weight loss of crazed PLA/PAni film increased to 42%, higher than that of non-crazed PLA/PAni film with only 31%. The nucleation of crazes increases the fragmentation and depolymerization of PLA/PAni film that induced microbial attack and led to higher weight loss. In conclusion, the presence of crazes in PLA/PAni film significantly improved enzymes' action, speeding up the polymer film's biodegradability.
Differential effects of sPLA2-GV and GX on cellular proliferation and lipid accumulation in HT29 colon cancer cells

Yap WH, Phang SW, Ahmed N, Lim YM

Mol Cell Biochem, 2018 Oct;447(1-2):93-101.
PMID: 29374817 DOI: 10.1007/s11010-018-3295-y

Secretory phospholipase A2 (sPLA2) group of enzymes have been shown to hydrolyze phospholipids, among which sPLA2 Group V (GV) and Group X (GX) exhibit high selectivity towards phosphatidylcholine-rich cellular plasma membranes. The enzymes have recently emerged as key regulators in lipid droplets formation and it is hypothesized that sPLA2-GV and GX enhanced cell proliferation and lipid droplet accumulation in colon cancer cells (HT29). In this study, cell viability and lipid droplet accumulation were assessed by Resazurin assay and Oil-Red-O staining. Interestingly, both sPLA2-GV and GX enzymes reduced intracellular lipid droplet accumulation and did not significantly affect cell proliferation in HT29 cells. Incubation with varespladib, a pan-inhibitor of sPLA2-Group IIA/V/X, further suppressed lipid droplets accumulation in sPLA2-GV but have no effects in sPLA2-GX-treated cells. Further studies using catalytically inactive sPLA2 enzymes showed that the enzymes intrinsic catalytic activity is required for the net reduction of lipid accumulation. Meanwhile, inhibition of intracellular phospholipases (iPLA2-γ and cPLA2-α) unexpectedly enhanced lipid droplet accumulation in both sPLA2-GV and GX-treated cells. The findings suggested an interconnected relationship between extracellular and intracellular phospholipases in lipid cycling. Previous studies indicated that sPLA2 enzymes are linked to cancer development due to their ability to induce release of arachidonic acid and eicosanoids as well as the stimulation of lipid droplet formation. This study showed that the two enzymes work in a distinct manner and they neither confer proliferative advantage nor enhanced the net lipid droplet accumulation in HT29 cells.
Maslinic acid suppresses macrophage foam cells formation: Regulation of monocyte recruitment and macrophage lipids homeostasis

Phang SW, Ooi BK, Ahemad N, Yap WH

Vascul Pharmacol, 2020 03 19;128-129:106675.
PMID: 32200116 DOI: 10.1016/j.vph.2020.106675

The transformation of macrophages to foam cells is a critical component in atherosclerotic lesion formation. Maslinic acid (MA), a novel natural pentacyclic triterpene, has cardioprotective and anti-inflammatory properties. It is hypothesized that MA can suppress monocyte recruitment to endothelial cells and inhibit macrophage foam cells formation. Previous study shows that MA inhibits inflammatory effects induced by sPLA2-IIA, including foam cells formation. This study elucidates the regulatory effect of MA in monocyte recruitment, macrophage lipid accumulation and cholesterol efflux. Our findings demonstrate that MA inhibits THP-1 monocyte adhesion to HUVEC cells in a TNFα-dependent and independent manner, but it induces trans-endothelial migration marginally at low concentration. MA down-regulates both gene and protein expression on VCAM-1 and MCP-1 in HUVECs. We further showed that MA suppresses macrophage foam cells formation, as indicated from the Oil-Red-O staining and flow cytometric analysis of intracellular lipids accumulation. The effects observed may be attributed to the antioxidant properties of MA where it was shown to suppress CuSO4-induced lipid peroxidation. MA inhibits scavenger receptors SR-A and CD36 expression while enhancing cholesterol efflux. MA enhances cholesterol efflux transporters ABCA1 and ABCG1 genes expression marginally without inducing its protein expression. In this study, MA was shown to target important steps that contribute to foam cell formation, including its ability in reducing monocytes adhesion to endothelial cells and LDL peroxidation, down-regulating scavenger receptors expression as well as enhancing cholesterol efflux, which might be of great importance in the context of atherosclerosis prevention and treatment.
Exploring the potential of intermetallic alloys as implantable biomaterials: A comprehensive review

Nasiri-Tabrizi B, Basirun WJ, Walvekar R, Yeong CH, Phang SW

Biomater Adv, 2024 Apr 16;161:213854.
PMID: 38703541 DOI: 10.1016/j.bioadv.2024.213854

This review delves into the utilization of intermetallic alloys (IMAs) as advanced biomaterials for medical implants, scrutinizing their conceptual framework, fabrication challenges, and diverse manufacturing techniques such as casting, powder metallurgy, and additive manufacturing. Manufacturing techniques such as casting, powder metallurgy, additive manufacturing, and injection molding are discussed, with specific emphasis on achieving optimal grain sizes, surface roughness, and mechanical properties. Post-treatment methods aimed at refining surface quality, dimensional precision, and mechanical properties of IMAs are explored, including the use of heat treatments to enhance biocompatibility and corrosion resistance. The review presents an in-depth examination of IMAs-based implantable biomaterials, covering lab-scale developments and commercial-scale implants. Specific IMAs such as Nickel Titanium, Titanium Aluminides, Iron Aluminides, Magnesium-based IMAs, Zirconium-based IMAs, and High-entropy alloys (HEAs) are highlighted, with detailed discussions on their mechanical properties, including strength, elastic modulus, and corrosion resistance. Future directions are outlined, with an emphasis on the anticipated growth in the orthopedic devices market and the role of IMAs in meeting this demand. The potential of porous IMAs in orthopedics is explored, with emphasis on achieving optimal pore sizes and distributions for enhanced osseointegration. The review concludes by highlighting the ongoing need for research and development efforts in IMAs technologies, including advancements in design and fabrication techniques.
In vitro evaluation of the involvement of Nrf2 in maslinic acid-mediated anti-inflammatory effects in atheroma pathogenesis

Ooi BK, Phang SW, Yong PVC, Chellappan DK, Dua K, Khaw KY, et al.

Life Sci, 2021 Aug 01;278:119658.
PMID: 34048809 DOI: 10.1016/j.lfs.2021.119658

AIMS: Maslinic acid (MA) is a naturally occurring pentacyclic triterpene known to exert cardioprotective effects. This study aims to investigate the involvement of nuclear factor erythroid 2-related factor 2 (Nrf2) for MA-mediated anti-inflammatory effects in atheroma pathogenesis in vitro, including evaluation of tumor necrosis factor-alpha (TNF-α)-induced monocyte recruitment, oxidized low-density lipoprotein (oxLDL)-induced scavenger receptors expression, and nuclear factor-kappa B (NF-ĸB) activity in human umbilical vein endothelial cells (HUVECS) and human acute monocytic leukemia cell line (THP-1) macrophages.
MATERIALS AND METHODS: An in vitro monocyte recruitment model utilizing THP-1 and HUVECs was developed to evaluate TNF-α-induced monocyte adhesion and trans-endothelial migration. To study the role of Nrf2 for MA-mediated anti-inflammatory effects, Nrf2 inhibitor ML385 was used as the pharmacological inhibitor. The expression of Nrf2, monocyte chemoattractant protein-1 (MCP-1), vascular cell adhesion molecule 1 (VCAM-1), cluster of differentiation 36 (CD36), and scavenger receptor type A (SR-A) in HUVECs and THP-1 macrophages were investigated using RT-qPCR and Western blotting. The NF-κB activity was determined using NF-κB (p65) Transcription Factor Assay Kit.
KEY FINDINGS: The results showed opposing effects of MA on Nrf2 expression in HUVECs and THP-1 macrophages. MA suppressed TNF-α-induced Nrf2 expression in HUVECs, but enhanced its expression in THP-1 macrophages. Combined effects of MA and ML385 suppressed MCP-1, VCAM-1, and SR-A expressions. Intriguingly, at the protein level, ML385 selectively inhibited SR-A but enhanced CD36 expression. Meanwhile, ML385 further enhanced MA-mediated inhibition of NF-κB activity in HUVECs. This effect, however, was not observed in THP-1 macrophages.
SIGNIFICANCE: MA attenuated foam cell formation by suppressing VCAM-1, MCP-1, and SR-A expression, as well as NF-κB activity, possibly through Nrf2 inhibition. The involvement of Nrf2 for MA-mediated anti-inflammatory effects however differs between HUVECs and macrophages. Future investigations are warranted for a detailed evaluation of the contributing roles of Nrf2 in foam cells formation.