Browse publications by year: 2021

Dynamic Mechanical Properties and Thermal Properties of Longitudinal Basalt/Woven Glass Fiber Reinforced Unsaturated Polyester Hybrid Composites

Haris NIN, Ilyas RA, Hassan MZ, Sapuan SM, Afdzaluddin A, Jamaludin KR, et al.

Polymers (Basel), 2021 Sep 29;13(19).
PMID: 34641159 DOI: 10.3390/polym13193343

This study investigates the mechanical, thermal, and chemical properties of basalt/woven glass fiber reinforced polymer (BGRP) hybrid polyester composites. The Fourier transform infrared spectroscopy (FTIR) was used to explore the chemical aspect, whereas the dynamic mechanical analysis (DMA) and thermomechanical analysis (TMA) were performed to determine the mechanical and thermal properties. The dynamic mechanical properties were evaluated in terms of the storage modulus, loss modulus, and damping factor. The FTIR results showed that incorporating single and hybrid fibers in the matrix did not change the chemical properties. The DMA findings revealed that the B7.5/G22.5 composite with 7.5 wt% of basalt fiber (B) and 22.5 wt% of glass fiber (G) exhibited the highest elastic and viscous properties, as it exhibited the higher storage modulus (8.04 × 109 MPa) and loss modulus (1.32 × 109 MPa) compared to the other samples. All the reinforced composites had better damping behavior than the neat matrix, but no further enhancement was obtained upon hybridization. The analysis also revealed that the B22.5/G7.5 composite with 22.5 wt% of basalt fiber and 7.5 wt% of glass fiber had the highest Tg at 70.80 °C, and increased by 15 °C compared to the neat matrix. TMA data suggested that the reinforced composites had relatively low dimensional stabilities than the neat matrix, particularly between 50 to 80 °C. Overall, the hybridization of basalt and glass fibers in unsaturated polyester formed composites with higher mechanical and thermal properties than single reinforced composites.
Chitosan-Coated 5-Fluorouracil Incorporated Emulsions as Transdermal Drug Delivery Matrices

Khan TA, Azad AK, Fuloria S, Nawaz A, Subramaniyan V, Akhlaq M, et al.

Polymers (Basel), 2021 Sep 29;13(19).
PMID: 34641162 DOI: 10.3390/polym13193345

The purpose of the present study was to develop emulsions encapsulated by chitosan on the outer surface of a nano droplet containing 5-fluorouracil (5-FU) as a model drug. The emulsions were characterized in terms of size, pH and viscosity and were evaluated for their physicochemical properties such as drug release and skin permeation in vitro. The emulsions containing tween 80 (T80), sodium lauryl sulfate, span 20, and a combination of polyethylene glycol (PEG) and T20 exhibited a release of 88%, 86%, 90% and 92%, respectively. Chitosan-modified emulsions considerably controlled the release of 5-FU compared to a 5-FU solution (p < 0.05). All the formulations enabled transportation of 5-FU through a rat's skin. The combination (T80, PEG) formulation showed a good penetration profile. Different surfactants showed variable degrees of skin drug retention. The ATR-FTIR spectrograms revealed that the emulsions mainly affected the fluidization of lipids and proteins of the stratum corneum (SC) that lead to enhanced drug permeation and retention across the skin. The present study concludes that the emulsions containing a combination of surfactants (Tween) and a co-surfactant (PEG) exhibited the best penetration profile, prevented the premature release of drugs from the nano droplet, enhanced the permeation and the retention of the drug across the skin and had great potential for transdermal drug delivery. Therefore, chitosan-coated 5-FU emulsions represent an excellent possibility to deliver a model drug as a transdermal delivery system.
Chitosan-Based Accelerated Portland Cement Promotes Dentinogenic/Osteogenic Differentiation and Mineralization Activity of SHED

Subhi H, Husein A, Mohamad D, Nik Abdul Ghani NR, Nurul AA

Polymers (Basel), 2021 Sep 30;13(19).
PMID: 34641172 DOI: 10.3390/polym13193358

Calcium silicate-based cements (CSCs) are widely used in various endodontic treatments to promote wound healing and hard tissue formation. Chitosan-based accelerated Portland cement (APC-CT) is a promising and affordable material for endodontic use. This study investigated the effect of APC-CT on apoptosis, cell attachment, dentinogenic/osteogenic differentiation and mineralization activity of stem cells from human exfoliated deciduous teeth (SHED). APC-CT was prepared with various concentrations of chitosan (CT) solution (0%, 0.625%, 1.25% and 2.5% (w/v)). Cell attachment was determined by direct contact analysis using field emission scanning electron microscopy (FESEM); while the material extracts were used for the analyses of apoptosis by flow cytometry, dentinogenic/osteogenic marker expression by real-time PCR and mineralization activity by Alizarin Red and Von Kossa staining. The cells effectively attached to the surfaces of APC and APC-CT, acquiring flattened elongated and rounded-shape morphology. Treatment of SHED with APC and APC-CT extracts showed no apoptotic effect. APC-CT induced upregulation of DSPP, MEPE, DMP-1, OPN, OCN, OPG and RANKL expression levels in SHED after 14 days, whereas RUNX2, ALP and COL1A1 expression levels were downregulated. Mineralization assays showed a progressive increase in the formation of calcium deposits in cells with material containing higher CT concentration and with incubation time. In conclusion, APC-CT is nontoxic and promotes dentinogenic/osteogenic differentiation and mineralization activity of SHED, indicating its regenerative potential as a promising substitute for the commercially available CSCs to induce dentin/bone regeneration.
Role of Mg(NO3)2 as Defective Agent in Ameliorating the Electrical Conductivity, Structural and Electrochemical Properties of Agarose-Based Polymer Electrolytes

Ali NI, Abidin SZZ, Majid SR, Jaafar NK

Polymers (Basel), 2021 Sep 30;13(19).
PMID: 34641173 DOI: 10.3390/polym13193357

Polymer electrolytes based on agarose dissolved in DMSO solvent complexed with different weight percentages of Mg(NO3)2 ranging from 0 to 35 wt% were prepared using a solution casting method. Electrochemical impedance spectroscopy (EIS) was applied to study the electrical properties of this polymer electrolyte, such as ionic conductivity at room and different temperatures, dielectric and modulus properties. The highest conducting film has been obtained at 1.48 × 10-5 S·cm-1 by doping 30 wt% of Mg(NO3)2 into the polymer matrix at room temperature. This high ionic conductivity value is achieved due to the increase in the amorphous nature of the polymer electrolyte, as proven by X-ray diffractometry (XRD), where broadening of the amorphous peak can be observed. The intermolecular interactions between agarose and Mg(NO3)2 are studied by Fourier transform infrared (FTIR) spectroscopy by observing the presence of -OH, -CH, N-H, CH3, C-O-C, C-OH, C-C and 3,6-anhydrogalactose bridges in the FTIR spectra. The electrochemical properties for the highest conducting agarose-Mg(NO3)2 polymer electrolyte are stable up to 3.57 V, which is determined by using linear sweep voltammetry (LSV) and supported by cyclic voltammetry (CV) that proves the presence of Mg2+ conduction.
Fulltext Use of Industrial Wastes as Sustainable Nutrient Sources for Bacterial Cellulose (BC) Production: Mechanism, Advances, and Future Perspectives

Kadier A, Ilyas RA, Huzaifah MRM, Harihastuti N, Sapuan SM, Harussani MM, et al.

Polymers (Basel), 2021 Sep 30;13(19).
PMID: 34641185 DOI: 10.3390/polym13193365

A novel nanomaterial, bacterial cellulose (BC), has become noteworthy recently due to its better physicochemical properties and biodegradability, which are desirable for various applications. Since cost is a significant limitation in the production of cellulose, current efforts are focused on the use of industrial waste as a cost-effective substrate for the synthesis of BC or microbial cellulose. The utilization of industrial wastes and byproduct streams as fermentation media could improve the cost-competitiveness of BC production. This paper examines the feasibility of using typical wastes generated by industry sectors as sources of nutrients (carbon and nitrogen) for the commercial-scale production of BC. Numerous preliminary findings in the literature data have revealed the potential to yield a high concentration of BC from various industrial wastes. These findings indicated the need to optimize culture conditions, aiming for improved large-scale production of BC from waste streams.
Efficient Synthesis and Characterization of Polyaniline@Aluminium-Succinate Metal-Organic Frameworks Nanocomposite and Its Application for Zn(II) Ion Sensing

Alsafrani AE, Adeosun WA, Marwani HM, Khan I, Jawaid M, Asiri AM, et al.

Polymers (Basel), 2021 Sep 30;13(19).
PMID: 34641198 DOI: 10.3390/polym13193383

A new class of conductive metal-organic framework (MOF), polyaniline- aluminum succinate (PANI@Al-SA) nanocomposite was prepared by oxidative polymerization of aniline monomer using potassium persulfate as an oxidant. Several analytical techniques such as FTIR, FE-SEM, EDX, XRD, XPS and TGA-DTA were utilized to characterize the obtained MOFs nanocomposite. DC electrical conductivity of polymer-MOFs was determined by four probe method. A bare glassy carbon electrode (GCE) was modified by nafion/PANI@Al-SA, and examined for Zn (II) ion detection. Modified electrode showed improved efficiency by 91.9%. The modified electrode (PANI@Al-SA/nafion/GCE) exhibited good catalytic property and highly selectivity towards Zn(II) ion. A linear dynamic range of 2.8-228.6 µM was obtained with detection limit of LOD 0.59 µM and excellent sensitivity of 7.14 µA µM-1 cm-2. The designed procedure for Zn (II) ion detection in real sample exhibited good stability in terms of repeatability, reproducibility and not affected by likely interferents. Therefore, the developed procedure is promising for quantification of Zn(II) ion in real samples.
Advocating Electrically Conductive Scaffolds with Low Immunogenicity for Biomedical Applications: A Review

Ahmad Ruzaidi DA, Mahat MM, Shafiee SA, Mohamed Sofian Z, Mohmad Sabere AS, Ramli R, et al.

Polymers (Basel), 2021 Oct 02;13(19).
PMID: 34641210 DOI: 10.3390/polym13193395

Scaffolds support and promote the formation of new functional tissues through cellular interactions with living cells. Various types of scaffolds have found their way into biomedical science, particularly in tissue engineering. Scaffolds with a superior tissue regenerative capacity must be biocompatible and biodegradable, and must possess excellent functionality and bioactivity. The different polymers that are used in fabricating scaffolds can influence these parameters. Polysaccharide-based polymers, such as collagen and chitosan, exhibit exceptional biocompatibility and biodegradability, while the degradability of synthetic polymers can be improved using chemical modifications. However, these modifications require multiple steps of chemical reactions to be carried out, which could potentially compromise the end product's biosafety. At present, conducting polymers, such as poly(3,4-ethylenedioxythiophene) poly(4-styrenesulfonate) (PEDOT: PSS), polyaniline, and polypyrrole, are often incorporated into matrix scaffolds to produce electrically conductive scaffold composites. However, this will reduce the biodegradability rate of scaffolds and, therefore, agitate their biocompatibility. This article discusses the current trends in fabricating electrically conductive scaffolds, and provides some insight regarding how their immunogenicity performance can be interlinked with their physical and biodegradability properties.
Hybrid and Synthetic FRP Composites under Different Strain Rates: A Review

Farokhi Nejad A, Bin Salim MY, Rahimian Koloor SS, Petrik S, Yahya MY, Abu Hassan S, et al.

Polymers (Basel), 2021 Oct 02;13(19).
PMID: 34641214 DOI: 10.3390/polym13193400

As a high-demand material, polymer matrix composites are being used in many advanced industrial applications. Due to ecological issues in the past decade, some attention has been paid to the use of natural fibers. However, using only natural fibers is not desirable for advanced applications. Therefore, hybridization of natural and synthetic fibers appears to be a good solution for the next generation of polymeric composite structures. Composite structures are normally made for various harsh operational conditions, and studies on loading rate and strain-dependency are essential in the design stage of the structures. This review aimed to highlight the different materials' content of hybrid composites in the literature, while addressing the different methods of material characterization for various ranges of strain rates. In addition, this work covers the testing methods, possible failure, and damage mechanisms of hybrid and synthetic FRP composites. Some studies about different numerical models and analytical methods that are applicable for composite structures under different strain rates are described.
Waste NR Latex Based-Precursors as Carbon Source for CNTs Eco-Fabrications

Hazan MA, Chan KF, Jofri KA, Mamat MS, Endot NA, Liza S, et al.

Polymers (Basel), 2021 Oct 04;13(19).
PMID: 34641224 DOI: 10.3390/polym13193409

In this work, the potential of utilizing a waste latex-based precursor (i.e., natural rubber glove (NRG)) as a carbon source for carbon nanotube (CNT) fabrication via chemical vapor deposition has been demonstrated. Gas chromatography-mass spectroscopy (GC-MS) analysis reveals that the separation of the lightweight hydrocarbon chain from the heavier long chain differs in hydrocarbon contents in the NRG fraction (NRG-L). Both solid NRG (NRG-S) and NRG-L samples contain >63% carbon, <0.6% sulfur and <0.08% nitrogen content, respectively, as per carbon-nitrogen-sulfur (CNS) analysis. Growth of CNTs on the samples was confirmed by Raman spectra, SEM and TEM images, whereby it was shown that NRG-S is better than NRG-L in terms of synthesized CNTs yield percentage with similar quality. The optimum vaporization and reaction temperatures were 350 and 800 °C, respectively, considering the balance of good yield percentage (26.7%) and quality of CNTs (ID/IG = 0.84 ± 0.08, diameter ≈ 122 nm) produced. Thus, utilization of waste NRG as a candidate for carbon feedstock to produce value-added CNTs products could be a significant approach for eco-technology.
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.
Physical, Mechanical, and Morphological Properties of Hybrid Cyrtostachys renda/Kenaf Fiber Reinforced with Multi-Walled Carbon Nanotubes (MWCNT)-Phenolic Composites

Loganathan TM, Hameed Sultan MT, Jawaid M, Ahsan Q, Naveen J, Shah AUM, et al.

Polymers (Basel), 2021 Oct 08;13(19).
PMID: 34641263 DOI: 10.3390/polym13193448

Adequate awareness of sustainable materials and eco-legislation have inspired researchers to identify alternative sustainable and green composites for synthetic fiber-reinforced polymer composites in the automotive and aircraft industries. This research focused on investigating the physical, mechanical, and morphological properties of different hybrid Cyrtostachys renda (CR)/kenaf fiber (K) (10C:0K, 7C:3K, 5C:5K, 3C:7K, 0C:10K) reinforced with 0.5 wt% MWCNT-phenolic composites. We incorporated 0.5 wt% of MWCNT into phenolic resin (powder) using a ball milling process for 25 h to achieve homogeneous distribution. The results revealed that CR fiber composites showed higher voids content (12.23%) than pure kenaf fiber composites (6.57%). CR fiber phenolic composite was more stable to the swelling tendency, resulting in the lowest percentage of swelling rate (4.11%) compared to kenaf composite (5.29%). The addition of kenaf fiber into CR composites had improved the tensile, flexural, and impact properties. The highest tensile and flexural properties were found for weight fraction of CR and kenaf fiber at 5C:5K (47.96 MPa) and 3C:7K (90.89 MPa) composites, respectively. In contrast, the highest impact properties were obtained for 0C:10K composites (9.56 kJ/m2). Based on the FE-SEM image, the CR fiber lumen was larger in comparison to kenaf fiber. The lumen of CR fiber was attributed to higher void and water absorption, lower mechanical properties compared to kenaf fiber. 5C:5K composite was selected as an optimal hybrid composite, based on the TOPSIS method. This hybrid composite can be used as an interior component (non-load-bearing structures) in the aviation and automotive sectors.
Fulltext Psychrotolerant Mesorhizobium sp. Isolated from Temperate and Cold Desert Regions Solubilizes Potassium and Produces Multiple Plant Growth Promoting Metabolites

Baba ZA, Hamid B, Sheikh TA, Alotaibi SH, El Enshasy HA, Ansari MJ, et al.

Molecules, 2021 Sep 23;26(19).
PMID: 34641302 DOI: 10.3390/molecules26195758

Soil potassium (K) supplement depends intensively on the application of chemical fertilizers, which have substantial harmful environmental effects. However, some bacteria can act as inoculants by converting unavailable and insoluble K forms into plant-accessible forms. Such bacteria are an eco-friendly approach for enhancing plant K absorption and consequently reducing utilization of chemical fertilization. Therefore, the present research was undertaken to isolate, screen, and characterize the K solubilizing bacteria (KSB) from the rhizosphere soils of northern India. Overall, 110 strains were isolated, but only 13 isolates showed significant K solubilizing ability by forming a halo zone on solid media. They were further screened for K solubilizing activity at 0 °C, 1 °C, 3 °C, 5 °C, 7 °C, 15 °C, and 20 °C for 5, 10, and 20 days. All the bacterial isolates showed mineral K solubilization activity at these different temperatures. However, the content of K solubilization increased with the upsurge in temperature and period of incubation. The isolate KSB (Grz) showed the highest K solubilization index of 462.28% after 48 h of incubation at 20 °C. The maximum of 23.38 µg K/mL broth was solubilized by the isolate KSB (Grz) at 20 °C after 20 days of incubation. Based on morphological, biochemical, and molecular characterization (through the 16S rDNA approach), the isolate KSB (Grz) was identified as Mesorhizobium sp. The majority of the strains produced HCN and ammonia. The maximum indole acetic acid (IAA) (31.54 µM/mL) and cellulase (390 µM/mL) were produced by the isolate KSB (Grz). In contrast, the highest protease (525.12 µM/mL) and chitinase (5.20 µM/mL) activities were shown by standard strain Bacillus mucilaginosus and KSB (Gmr) isolate, respectively.

MeSH terms: DNA, Bacterial/genetics; DNA, Ribosomal/genetics; Phylogeny; Plant Growth Regulators/metabolism*; Potassium/chemistry*; RNA, Ribosomal, 16S/genetics; Soil Microbiology; Solubility; Temperature; Sequence Analysis, DNA/methods*; Mesorhizobium/classification; Mesorhizobium/growth & development*; Mesorhizobium/isolation & purification; Mesorhizobium/metabolism; Secondary Metabolism
Fulltext NMF-Based Approach for Missing Values Imputation of Mass Spectrometry Metabolomics Data

Xu J, Wang Y, Xu X, Cheng KK, Raftery D, Dong J

Molecules, 2021 Sep 24;26(19).
PMID: 34641330 DOI: 10.3390/molecules26195787

In mass spectrometry (MS)-based metabolomics, missing values (NAs) may be due to different causes, including sample heterogeneity, ion suppression, spectral overlap, inappropriate data processing, and instrumental errors. Although a number of methodologies have been applied to handle NAs, NA imputation remains a challenging problem. Here, we propose a non-negative matrix factorization (NMF)-based method for NA imputation in MS-based metabolomics data, which makes use of both global and local information of the data. The proposed method was compared with three commonly used methods: k-nearest neighbors (kNN), random forest (RF), and outlier-robust (ORI) missing values imputation. These methods were evaluated from the perspectives of accuracy of imputation, retrieval of data structures, and rank of imputation superiority. The experimental results showed that the NMF-based method is well-adapted to various cases of data missingness and the presence of outliers in MS-based metabolic profiles. It outperformed kNN and ORI and showed results comparable with the RF method. Furthermore, the NMF method is more robust and less susceptible to outliers as compared with the RF method. The proposed NMF-based scheme may serve as an alternative NA imputation method which may facilitate biological interpretations of metabolomics data.

MeSH terms: Algorithms; Mass Spectrometry; Cluster Analysis; Computational Biology/methods*; Metabolomics/methods*
Fulltext Hexaconazole-Micelle Nanodelivery System Prepared Using Different Surfactants for Ganoderma Antifungal Application

Mustafa IF, Hussein MZ, Idris AS, Hilmi NHZ, Fakurazi S

Molecules, 2021 Sep 26;26(19).
PMID: 34641379 DOI: 10.3390/molecules26195837

Reports on fungicide-based agronanochemicals in combating disastrous basal stem rot disease in the oil palm industry are scant. Herein, we describe the potential of fungicide nanodelivery agents based on hexaconazole-micelle systems produced using three different surfactants; sodium dodecylbenze sulfonate (SDBS), sodium dodecyl sulfate (SDS) and Tween 80 (T80). The resulting nanodelivery systems were characterized and the results supported the encapsulation of the fungicide into the micelles of the surfactants. We have investigated in detail the size-dependent effects of the as-synthesized micelles towards the inhibition growth of Ganoderma Boninense fungi. All the nanodelivery systems indicate that their size decreased as the surfactant concentration was increased, and it directly affects the fungal inhibition. It was also found that Tween 80, a non-ionic surfactant gave the lowest effective concentration, the EC50 value of 2, on the pathogenic fungus Ganoderma boninense compared to the other anionic surfactants; SDBS and SDS. This study opens up a new generation of agronanofungicide of better efficacy for Ganoderma disease treatment.

MeSH terms: Antifungal Agents/pharmacology*; Antifungal Agents/chemistry; Micelles*; Surface-Active Agents/chemistry*; Triazoles/pharmacology*; Triazoles/chemistry; Drug Delivery Systems*; Ganoderma/drug effects*; Nanoparticles/administration & dosage*; Nanoparticles/chemistry
Viscoelastic Properties and Thermal Stability of Nanohydroxyapatite Reinforced Poly-Lactic Acid for Load Bearing Applications

Michael FM, Khalid M, Raju G, Ratnam CT, Walvekar R, Mubarak NM

Molecules, 2021 Sep 27;26(19).
PMID: 34641395 DOI: 10.3390/molecules26195852

We studied the reinforcing effects of treated and untreated nanohydroxyapatite (NHA) on poly-lactic acid (PLA). The NHA surface was treated with three different types of chemicals; 3-aminopropyl triethoxysilane (APTES), sodium n-dodecyl sulfate (SDS) and polyethylenimine (PEI). The nanocomposite samples were prepared using melt mixing techniques by blending 5 wt% untreated NHA and 5 wt% surface-treated NHA (mNHA). Based on the FESEM images, the interfacial adhesion between the mNHA filler and PLA matrix was improved upon surface treatment in the order of mNHA (APTES) > mNHA (SDS) > mNHA (PEI). As a result, the PLA-5wt%mNHA (APTES) nanocomposite showed increased viscoelastic properties such as storage modulus, damping parameter, and creep permanent deformation compared to pure PLA. Similarly, PLA-5wt%mNHA (APTES) thermal properties improved, attaining higher Tc and Tm than pure PLA, reflecting the enhanced nucleating effect of the mNHA (APTES) filler.
Efficient Catalytic Reduction of 4-Nitrophenol Using Copper(II) Complexes with N,O-Chelating Schiff Base Ligands

Garba HW, Abdullahi MS, Jamil MSS, Endot NA

Molecules, 2021 Sep 28;26(19).
PMID: 34641418 DOI: 10.3390/molecules26195876

The reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride was used as a model to test the catalytic activity of copper(II) complexes containing N,O-chelating Schiff base ligands. In this study, a series of copper(II) complexes containing respective Schiff base ligands, N'-salicylidene-2-aminophenol (1), N'-salicylidene-2-aminothiazole (2), and N,N'-bis(salicylidene)-o-phenylenediamine (3), were synthesized and characterized by elemental analysis, Fourier transform infrared (FT-IR), UV-Visible (UV-Vis) and electron paramagnetic resonance (EPR) spectroscopies. The results from the 4-nitrophenol reduction showed that 3 has the highest catalytic activities with 97.5% conversion, followed by 2 and 1 with 95.2% and 90.8% conversions, respectively. The optimization of the catalyst amount revealed that 1.0 mol% of the catalyst was the most optimized amount with the highest conversion compared to the other doses, 0.5 mol% and 1.5 mol%. Recyclability and reproducibility tests confirmed that all three complexes were active, efficient, and possess excellent reproducibility with consistent catalytic performances and could be used again without a major decrease in the catalytic activity.
Fulltext Development of Antibacterial, Degradable and pH-Responsive Chitosan/Guar Gum/Polyvinyl Alcohol Blended Hydrogels for Wound Dressing

Khan MUA, Iqbal I, Ansari MNM, Razak SIA, Raza MA, Sajjad A, et al.

Molecules, 2021 Sep 30;26(19).
PMID: 34641480 DOI: 10.3390/molecules26195937

The present research is based on the fabrication preparation of CS/PVA/GG blended hydrogel with nontoxic tetra orthosilicate (TEOS) for sustained paracetamol release. Different TEOS percentages were used because of their nontoxic behavior to study newly designed hydrogels' crosslinking and physicochemical properties. These hydrogels were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and wetting to determine the functional, surface morphology, hydrophilic, or hydrophobic properties. The swelling analysis in different media, degradation in PBS, and drug release kinetics were conducted to observe their response against corresponding media. The FTIR analysis confirmed the components added and crosslinking between them, and surface morphology confirmed different surface and wetting behavior due to different crosslinking. In various solvents, including water, buffer, and electrolyte solutions, the swelling behaviour of hydrogel was investigated and observed that TEOS amount caused less hydrogel swelling. In acidic pH, hydrogels swell the most, while they swell the least at pH 7 or higher. These hydrogels are pH-sensitive and appropriate for controlled drug release. These hydrogels demonstrated that, as the ionic concentration was increased, swelling decreased due to decreased osmotic pressure in various electrolyte solutions. The antimicrobial analysis revealed that these hydrogels are highly antibacterial against Gram-positive (Staphylococcus aureus and Bacillus cereus) and Gram negative (Pseudomonas aeruginosa and Escherichia coli) bacterial strains. The drug release mechanism was 98% in phosphate buffer saline (PBS) media at pH 7.4 in 140 min. To analyze drug release behaviour, the drug release kinetics was assessed against different mathematical models (such as zero and first order, Higuchi, Baker-Lonsdale, Hixson, and Peppas). It was found that hydrogel (CPG2) follows the Peppas model with the highest value of regression (R2 = 0.98509). Hence, from the results, these hydrogels could be a potential biomaterial for wound dressing in biomedical applications.

MeSH terms: Anti-Bacterial Agents/administration & dosage*; Anti-Bacterial Agents/chemistry; Bacteria/drug effects*; Bandages; Galactans/chemistry*; Mannans/chemistry*; Polyvinyl Alcohol/chemistry*; Wound Healing/drug effects*; Hydrogels/administration & dosage*; Hydrogels/chemistry; Chitosan/chemistry*; Plant Gums/chemistry*; Drug Liberation
Longitudinal extensive transverse myelitis following ChAdOx1 nCOV-19 vaccine: a case report

Tan WY, Yusof Khan AHK, Mohd Yaakob MN, Abdul Rashid AM, Loh WC, Baharin J, et al.

BMC Neurol, 2021 Oct 12;21(1):395.
PMID: 34641797 DOI: 10.1186/s12883-021-02427-x

BACKGROUND: Transverse myelitis (TM) is a relatively uncommon condition, and vaccine-associated myelitis is even rarer. Concern regarding neurological complications following vaccination escalated following the report of TM during the safety and efficacy trials of the COVID-19 vaccine.
CASE PRESENTATION: We report the first case of Longitudinal Extensive Transverse Myelitis (LETM) in Malaysia following administration of the chimpanzee adenovirus-vectored (ChAdOx1 nCoV-19) vaccine. A 25-year-old female presented with bilateral lower limb weakness and inability to walk with a sensory level up to T8 with absent visual symptoms. Urgent gadolinium-enhanced magnetic resonance imaging (MRI) of the spine showed long segment TM over the thoracic region. Cerebrospinal fluid autoantibodies for anti-aquaporin-4 and anti-myelin-oligodendrocyte were negative. A diagnosis of LETM following vaccination was made, and the patient was started on a high dose of intravenous methylprednisolone. The patient eventually made a recovery following treatment.
CONCLUSION: LETM is a rare but serious adverse reaction following vaccination. Previously reported cases showed an onset of symptoms between 10 to 14 days post-vaccination, suggesting a delayed immunogenic reaction. However, the incidence of myelitis in COVID-19 is much more common, far greater than the risk associated with vaccination.

MeSH terms: Adult; Female; Humans; Vaccines*; Myelin-Oligodendrocyte Glycoprotein
Fulltext Cross-cultural adaptation and validation of Malay version of Rapid Estimate of Adult Literacy in Dentistry (MREALD-30) among Orang Asli population in Malaysia

Rath A, Wong M, Pannuti CM, Hesarghatta Ramamurthy P, Fernandes B, Shelton A, et al.

BMC Oral Health, 2021 10 12;21(1):519.
PMID: 34641831 DOI: 10.1186/s12903-021-01866-9

BACKGROUND: The aim of this study was to adapt, translate and validate the Rapid Estimate of Adult Literacy in Dentistry (MREALD-30) instrument for the Orang Asli population in Malaysia.
METHODS: After translation and cross-cultural adaptation, interviews were conducted with 326 participants of the Temuan tribe from village Kampung Tering in Johol, Negeri Sembilan, Malaysia. The instrument's validity was assessed using the scores of MREALD-30, which were compared based on occupation, monthly household income, educational attainment, general literacy, use of dental services, and three dental outcomes. A questionnaire containing socio-behavioral information and validated Malay Oral Health Impact Profile (M-OHIP-14) was also administered. The reliability of the MREALD-30 was assessed by re-administering it to 30 subjects after two weeks. Its correlations evaluated convergent and discriminative validity of MREALD-30 with the level of education and dental visiting habits, monthly household income, respectively. Predictive validity was assessed with M-OHIP-14, while construct validity was evaluated by exploratory factor analysis using the Rasch model.
RESULTS: The internal consistency of the MREALD-30 measured by Cronbach's alpha was 0.89. The test-retest reliability was excellent (ICC 0.95, k = 0.85). MREALD-30 exhibited good construct validity. Rasch analysis showed two factors, and infit mean-square statistics for MREALD-30 were all within the desired range of 0.50-2.0. The discriminant validity and predictive validity were statistically significant (p
Determinants of smokeless tobacco use and prevalence among Sudanese adolescents

Othman M, Farid NDN, Aghamohammadi N, Danaee M

Arch Public Health, 2021 Oct 12;79(1):176.
PMID: 34641965 DOI: 10.1186/s13690-021-00699-w

BACKGROUND: Smokeless tobacco is a part of social and cultural life in Sudan. The affordability and availability of this kind of tobacco make it a fundamental issue in adolescents. The aim of this study is to investigate the extent of the use of smokeless tobacco in adolescents and its determinants.
METHODS: A school-based cross-sectional study was conducted in Khartoum state in Sudan. The study targeted male and female adolescents in secondary schools. A total of 3387 students from public and private schools participated in the study. Multistage random sampling was used to select the participants. The Arabic version questionnaire from the Global Youth Tobacco Survey (GYTS) was utilised to collect the data from the participants.
RESULTS: Among the participants, 57.3% were females and 42.7% were males. Students from private and public schools were 48.4 and 51.6%, respectively. The overall prevalence of those who had ever used smokeless tobacco was 7.6%, in which the prevalence among male students was 11.0% while among females was 5.0%. The determinant factors were male gender (OR 1.53 CI 95% 1.03-2.28), family structure (OR 1.52 CI 95% 1.03-2.23), exposure to second-hand smoke at home (OR 1.60 CI 95% 1.11-2.31), friends smoking cigarettes (OR 1.78 CI 95% 1.22-2.60), lack of restriction of selling tobacco to minors (OR 1.73 CI 95% 1.25-2.39), promotion of smokeless tobacco (OR 2.12 CI 95% 1.20-3.72) and low self-efficacy (OR 7.47 CI 95% 4.45-12.52).
CONCLUSION: A comprehensive prevention programme that enforces the prohibition of the promotion of smokeless tobacco and the selling of smokeless tobacco to minors is crucial. Moreover, the prevention programme should enhance adolescents' self-efficacy.

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