With increasing usage of polyethylene terephthalate (PET) wastes polluting the oceans and environment, the recycling of PET wastes has become a crucial issue to be overcome. In this article, a review ...of the different technologies that have been developed to recycle PET wastes and common routes for recycled PET (rPET) is presented. The impacts of varied recycling technologies on the properties of rPET are also discussed herein. The review also focuses on the recovered products by each of the technology and their uses that have been reincorporated into new applications for example, from plastic bottle wastes to 3D scaffolds for biomedical application. Different recycling technologies such as reactive extrusion, chemical recycling and dissolution/precipitation exhibit specific properties due to the influence of the different concepts from one technology to another. A new trend called electrospinning of rPET to produce nanofibers has also garnered attention to be used for different applications. This article will first introduce the recycling technologies concept, and then the properties of the recovered product will be discussed and finally, we will focus on the applications of rPET produced from each of the technologies in various fields such as construction, textile, filtration, and biomedical applications.
Polyethylene terephthalate (PET) is completely recyclable and among the most recycled plastic globally. Recycling of PET can be done through various ways including mechanical recycling such as reactive extrusion and also by chemical means which transforms the PET into its monomers or various valuable chemicals. Other recycling technologies include dissolution/precipitation as well as blending and compatibilization. Once PET has been recycled, it is known as recycled PET (rPET) and can be used in various applications such as construction and textile. Another route that is gaining massive attention for rPET is the fabrication of rPET fibrous membranes by electrospinning. These elctrospun rPET fibers provide more possibilities for engineered application of rPET such as air and water filtration purposes.
The key attributes of core-shell fibers are their ability to preserve bioactivity of incorporated-sensitive biomolecules (such as drug, protein, and growth factor) and subsequently control ...biomolecule release to the targeted microenvironments to achieve therapeutic effects. Such qualities are highly favorable for tissue engineering and drug delivery, and these features are not able to be offered by monolithic fibers. In this review, we begin with an overview on design requirement of core-shell fibers, followed by the summary of recent preparation methods of core-shell fibers, with focus on electrospinning-based techniques and other newly discovered fabrication approaches. We then highlight the importance and roles of core-shell fibers in tissue engineering and drug delivery, accompanied by thorough discussion on controllable release strategies of the incorporated bioactive molecules from the fibers. Ultimately, we touch on core-shell fibers-related challenges and offer perspectives on their future direction towards clinical applications.
In recent years, polymeric adsorbent is gaining more interest over classical adsorbents such as clays and activated carbon due to its tunable physicochemical properties, structural diversity, ...reusability and selectivity. Therefore, the aim of this article is to summarize the available information on the adsorption studies of dyes using PVA and PVA-based polymer composite adsorbents. These materials were reviewed with emphasis on the experimental parameters (initial dye concentration, pH, adsorbent dosage etc.) and outcomes of the various adsorption studies were discussed. Furthermore, the isotherm models, kinetic and thermodynamic of the adsorption studies involved were also summarized. This review outlines the rationale for using the PVA-based composite adsorbents which have demonstrated good removal efficiency for several dyes. Future perspectives of the research work are also being suggested.
Graphic Abstract
Electrospun polycaprolactone (PCL) nanofibers have emerged as a promising material in diverse biomedical applications due to their various favorable features. However, their application in the field ...of biosensors such as point-of-care lateral flow assays (LFA) has not been investigated. The present study demonstrates the use of electrospun PCL nanofibers as a reaction membrane for LFA. Electrospun PCL nanofibers were treated with NaOH solution for different concentrations and durations to achieve a desirable flow rate and optimum detection sensitivity in nucleic acid-based LFA. It was observed that the concentration of NaOH does not affect the physical properties of nanofibers, including average fiber diameter, average pore size and porosity. However, interestingly, a significant reduction of the water contact angle was observed due to the generation of hydroxyl and carboxyl groups on the nanofibers, which increased their hydrophilicity. The optimally treated nanofibers were able to detect synthetic Zika viral DNA (as a model analyte) sensitively with a detection limit of 0.5 nM. Collectively, the benefits such as low-cost of fabrication, ease of modification, porous nanofibrous structures and tunability of flow rate make PCL nanofibers a versatile alternative to nitrocellulose membrane in LFA applications. This material offers tremendous potential for a broad range of point-of-care applications.
The employment of individual poly(lactic acid) (PLA) or cellulose acetate (CA) electrospun fibers as bone tissue replacement was restricted by the weak mechanical properties of CA and the poor ...cell-affinity of PLA. In this study, core-shell fibers with PLA as the core component and CA as the shell layer were fabricated via coaxial electrospinning with significant improvements in the tensile strength and biocompatibility in comparison to individual PLA and CA fibers and blend PLA/CA fibers. The employment of a core-to-shell flow rate ratio of 0.25:0.5 mL/hr:mL/hr resulted in the formation of defect-free and uniformly distributed PLA-CA core-shell fibers (cs-PLA1-CA2) with the highest ultimate tensile strength (19.53 ± 1.68 MPa) and Young’s modulus (0.62 ± 0.09 GPa) among all core-shell fibers produced in this study. These tensile values match the tensile properties of native cancellous bone and represent around a 130% and 160% improvement in strength and stiffness compared to monolithic CA fibers, respectively. Higher weight fraction and improved crystallinity of PLA-core were revealed to contribute to this mechanical enhancement of cs-PLA1-CA2. An in vitro biocompatibility study was conducted using human fetal osteoblasts (hFOB). The results indicate improved cell distribution, better cell-scaffold attachment, and higher cell proliferation and alkaline phosphatase (ALP) activity of cs-PLA1-CA2 compared to monolithic PLA and blend PLA/CA fibers, while matching the growth performance of hFOB seeded on tissue culture polystyrene (TCP). The PLA-CA core-shell fibers produced in this study hold great promise for use as bone tissue scaffolds.
The growth of global food demand combined with the increased appeal to access different foods from every corner of the globe is forcing the food industry to look for alternative technologies to ...increase the shelf life. Essential oils (EOs) as naturally occurring functional ingredients have shown great prospects in active food packaging. EOs can inhibit the growth of superficial food pathogens, modify nutritious values without affecting the sensory qualities of food, and prolong the shelf life when used in food packaging as an active ingredient. Since 2016, various reports have demonstrated that combinations of electrospun fibers and encapsulated EOs could offer promising results when used as food packaging. Such electrospun platforms have encapsulated either pure EOs or their complexation with other antibacterial agents to prolong the shelf life of food products through sustained release of active ingredients. This paper presents a comprehensive review of the essential oil-loaded electrospun fibers that have been applied as active food packaging material.
Tissues are commonly defined as groups of cells that have similar structure and uniformly perform a specialized function. A lesser-known fact is that the placement of these cells within these tissues ...plays an important role in executing its functions, especially for neuronal cells. Hence, the design of a functional neural scaffold has to mirror these cell organizations, which are brought about by the configuration of natural extracellular matrix (ECM) structural proteins. In this review, we will briefly discuss the various characteristics considered when making neural scaffolds. We will then focus on the cellular orientation and axonal alignment of neural cells within their ECM and elaborate on the mechanisms involved in this process. A better understanding of these mechanisms could shed more light onto the rationale of fabricating the scaffolds for this specific functionality. Finally, we will discuss the scaffolds used in neural tissue engineering (NTE) and the methods used to fabricate these well-defined constructs.
In the quest on improving composite formulations for environmental sustainability, maleic acid (MA) cross‐linked poly(vinyl alcohol) (PVA)‐α‐chitin composites reinforced by oil palm empty fruit bunch ...fibers (OPEFB)‐derived nanocellulose crystals (NCC) had been successfully prepared. Based on the Fourier transform infrared (FTIR) spectroscopic analysis, it was proven that molecular interactions of the cross‐linker to the polymeric networks was through conjugated ester linkage. Differential scanning calorimetry (DSC) showed that the influence of MA was minimal toward crystallization in the PVA/chitin/NCC composite. Maximum tensile strength, elongation at break and Young's modulus of the respective PVA/chitin/NCC composites were achieved at different content of MA, dependent on the PVA/chitin mass ratio. Among all compositions, a maximum Young's modulus was achieved at 30 wt% MA loading in PVA/chitin‐30/NCC, amounting to 2,413.81 ± 167.36 MPa. Moreover, the mechanical properties and selected physicochemical properties (swelling, gel content, and contact angle) of the PVA/chitin/NCC composites could be tailored by varying the chitin content (10–30 wt%) and MA content (10–50 wt% based on total mass of composite). In brief, this chemically cross‐linked PVA‐based biocomposites formulated with sustainable resources exhibited tunable physicochemical and mechanical properties.
Possible esterification reactions between OH group of PVA or chitin and COOH group of MA upon treatment of PVA/chitin/NCC with MA: formation of bis‐esters, resulting to cross‐linking or formation of mono‐ester which results in grafting.
Reusable and eco-friendly poly(vinyl alcohol)/chitin/nanocellulose based biopolymer composite films were synthesized and characterized. Maleic acid (MA) was used as a crosslinker of the biopolymer ...composite film. The effect of constituent materials of the biopolymer composite film and the pH on removal of methylene blue (MB) dye from aqueous testing solution were studied by batch adsorption studies. The successful deposition of MB dye onto the adsorbent (biopolymer composite film) was confirmed using Fourier transform infrared spectroscopy (FTIR) analysis. Adsorption isotherm studies were fitted to the Freundlich model with the maximum adsorption capacity amounted to 467.5 mg/g. The adsorption kinetics were in conformance to the pseudo-second order model (
R
2
= 0.9924–0.9987). The point zero charge (pH
pzc
) of the adsorbents were investigated by pH drift method where the MA cross-linked adsorbents showed pH
pzc
values in the range of 8.05–8.55. Moreover, the best adsorption performance was observed in sample PVA/CT10/NCC/MA30, with calculated maximum adsorption capacity amounted to 467.5 mg/g. Thermodynamic studies showed that the adsorption were spontaneous, exothermic and less-ordered reactions. High adsorption reusability was determined for PVA/CT10/NCC/MA30 composite, with adsorption percentage of 83.67 ± 1.08% at the fifth cycle. All these positive results implied the potential application of PVA/Chitin/NCC composites for the MB dye’s adsorption from aqueous testing solution.
Background Upstroke time is the transit time from the nadir to peak of the waveform of pulse volume recording. The purpose of this study was to determine whether upstroke time at the ankle is a ...useful vascular marker for detecting patients with advanced atherosclerosis in combination with ankle-brachial index (ABI). Methods and Results We measured upstroke time and ABI in 2313 subjects (mean age, 61.2±15.3 years). The prevalence of coronary artery disease (CAD) was significantly higher in patients with prolonged upstroke time (≥180 ms) than in subjects with normal upstroke time (<180 ms) (29.6% versus 11.8%;
<0.001), with a significant association between prolonged upstroke time and an increased risk of CAD (odds ratio OR, 1.61; 95% CI, 1.07-2.44;
=0.02). In 1954 subjects with normal ABI (1.00 ≤ ABI ≤ 1.40), the prevalence of CAD was significantly higher in patients with prolonged upstroke time than in subjects with normal upstroke time (29.5% versus 10.6%;
<0.001), with a significant association between prolonged upstroke time and CAD (OR, 2.33; 95% CI, 1.41-3.87;
=0.001), whereas there was no significant association between upstroke time and CAD in subjects with low ABI (<1.00) (OR, 1.24; 95% CI, 0.72-2.16;
=0.44). Conclusions Upstroke time may be a useful vascular marker for detecting patients with CAD, especially in subjects with normal ABI who are usually considered not to have advanced atherosclerosis by ABI measurement alone. More attention should be paid to upstroke time for detecting patients with advanced atherosclerosis. Registration URL: https://www.umin.ac.jp; Unique identifier: UMIN000039512.
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