Search Results (14)

The escalating demand for sustainable materials has been fueling the rapid proliferation of the biopolymer market. Biodegradable polymers within natural habitats predominantly undergo degradation mediated by microorganisms. These microorganisms secrete enzymes that cleave long-chain polymers into smaller fragments for metabolic assimilation. This review is centered around dissecting the degradation mechanisms of specific biodegradable polymers, namely PLA, starch-based polymers, and plant fiber-based polymers. Recent investigations have unveiled that PLA exhibits augmented biocompatibility when combined with HA, and its degradation is subject to the influence of enzymatic and abiotic determinants. In the case of starch-based polymers, chemical or physical modifications can modulate their degradation kinetics, as evidenced by Wang et al.’s superhydrophobic starch-based nanocomposite cryogel. For plant fiber-based polymers, the effects of temperature, humidity, and cellulose degradation on their properties, along with the implications of various treatments and additives, are probed, as exemplified by Liu et al.’s study on jute/SiO₂/PP composites. Specifically, with respect to PLA, the polymerization process and the role of catalysts such as SnCl₂ in governing the structure and biodegradability are expounded in detail. The degradation of PLA in SBF and its interaction with β-TCP particles constitute crucial aspects. For starch-based polymers, the enzymatic degradation catalyzed by amylase and glucosidase and the environmental impacts of temperature and humidity, in addition to the structural ramifications of amylose and amylopectin, are further elucidated. In plant fiber-based polymers, the biodegradation of cellulose and the effects of plasma treatment, electron beam irradiation, nanoparticles, and crosslinking agents on water resistance and stability are explicated with experimental substantiation. This manuscript also delineates technological accomplishments. PLA incorporated with HA demonstrates enhanced biocompatibility and finds utility in drug delivery systems. Starch-based polymers can be engineered for tailored degradation. Plant fiber-based polymers acquire water resistance and durability through specific treatments or the addition of nanoparticles, thereby widening their application spectrum. Synthetic and surface modification methodologies can be harnessed to optimize these materials. This paper also consolidates reaction conditions, research techniques, their merits, and demerits and delves into the biodegradation reaction mechanisms of these polymers. A comprehensive understanding of these degradation mechanisms is conducive to their application and progression in the context of sustainable development and environmental conservation. Full article

Since currently used natural, nonrenewable phosphorus resources are estimated to be depleted in the next 30–200 years, phosphorus recovery from any phosphorus-rich residues has attracted great interest. In this study, phosphorus recovery from complex wastewater samples was investigated using continuous adsorption on cryogel column composited calcium silicate hydrate nanoparticles (CSH columns). The results showed that 99.99% of phosphate was recovered from a synthetic water sample (50 mg L⁻¹) using a 5 cm CSH column with a 5 mL min⁻¹ influent flow rate for 6 h while 82.82% and 97.58% of phosphate were recovered from household laundry wastewater (1.84 mg L⁻¹) and reverse osmosis concentrate (26.46 mg L⁻¹), respectively. The adsorption capacity decreased with an increasing flow rate but increased with increasing initial concentration and column height, and the obtained experimental data were better fitted to the Yoon–Nelson model (R² = 0.7723–0.9643) than to the Adams–Bohart model (R² = 0.6320–0.8899). The adsorption performance of phosphate was decreased 3.65 times in the presence of carbonate ions at a similar concentration, whereas no effect was obtained from nitrate and sulfate. The results demonstrate the potential of continuous-flow phosphate adsorption on the CSH column for the recovery of phosphate from complex wastewater samples. Full article

A continuous-flow system based on a green and cost-effective monolithic starch cryogel column was successfully developed for removing methylene blue (MB). The proposed column exhibited high removal efficiency (up to 99.9%) and adsorption capacity (25.4 mg·g⁻¹) for synthetic and real samples with an adsorbent cost of USD 0.02. The influence of various operation parameters, including the flow rate, initial concentration, column height, and temperature, on the MB removal efficiency was examined and reported. The MB removal efficiency remained >99% in the presence of potential interferences, highlighting the good performance of the cryogel column. The Yoon–Nelson dynamic model explained the MB adsorption better than the Bohart–Adams model, as indicated by the higher R² values (R² = 0.9890–0.9999) exhibited by the former and current trends of its parameters. The MB removal efficiency of the cryogel column remained at 62.7% after three reuse cycles. The wastewater containing MB collected from a local batik-production community enterprise in Phuket, Thailand was applied to the proposed continuous-flow system under optimum conditions, and results indicated that 99.7% of the MB present in 2.4 L of wastewater was removed. These results validate the excellent application potential of the cryogel column for the continuous-flow adsorption of MB. This study will facilitate future industrial applications and process designs of the continuous-flow system. Full article

In this study, a starch cryoaerogel formulation was developed as a carrier for poorly water-soluble drugs, like atorvastatin. Cryoaerogels were generated through a sol–gel method combined with a freeze-drying technique, and atorvastatin was incorporated into the obtained mesoporous systems during the solvent exchange stage. The formulated drug-loaded polymer structures were characterized in terms of their physicochemical properties, solid-state behavior, and cytotoxicity. They had a pore size of 27.56 nm and a drug loading size of 38.60%. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) analyses indicated that atorvastatin was successfully incorporated into the cryoaerogel pores. The amorphous nature of the loaded drug was confirmed via X-ray diffraction (XRD). Furthermore, after the atorvastatin incorporation into the cryogel, the volume of nitrogen adsorbed on one gram of cryoaerogel (Vm), as well as the specific surface area (aBET) were reduced. The comparison between the drug release profiles of crystalline atorvastatin and the loaded formulation of atorvastatin showed that by including the drug into the pores of the developed cryoaerogel matrix its solubility was significantly improved—the time for the dissolution of 30% pure atorvastatin (t_30%) was approximately 4 h, whereas the determined t_30% for the formulated cryoaerogels was only 1 h. Moreover, the data from the MTT assay illustrated that the designed cryoaerogel could be used as a safe oral atorvastatin delivery system. According to obtained results, it could be concluded that the starch cryoaerogel formulation is a promising candidate for oral delivery of poorly water-soluble therapeutic agents. Full article

In this work, the effect of iron(III) in the preparation of a conductive porous composite using a biomass waste-based starch template was evaluated. Biopolymers are obtained from natural sources, for instance, starch from potato waste, and its conversion into value-added products is highly significant in a circular economy. The biomass starch-based conductive cryogel was polymerized via chemical oxidation of 3,4-ethylenedioxythiophene (EDOT) using iron(III) p-toluenesulfonate as a strategy to functionalize porous biopolymers. Thermal, spectrophotometric, physical, and chemical properties of the starch template, starch/iron(III), and the conductive polymer composites were evaluated. The impedance data of the conductive polymer deposited onto the starch template confirmed that at a longer soaking time, the electrical performance of the composite was improved, slightly modifying its microstructure. The functionalization of porous cryogels and aerogels using polysaccharides as raw materials is of great interest for applications in electronic, environmental, and biological fields. Full article

Cryogel formation is an effective approach to produce porous scaffolds for tissue engineering. In this study, cryogelation was performed to produce boron-containing scaffolds for bone tissue engineering. A combination of the synthetic polymer, poly(vinyl alcohol) (PVA), and the natural polymers, chitosan and starch, was used to formulate the cryogels. Boron was used with a dual purpose: as an additive to alter gelation properties, and to exploit its bioactive effect since boron has been found to be involved in several metabolic pathways, including the promotion of bone growth. This project designs a fabrication protocol enabling the competition of both physical and chemical cross-linking reactions in the cryogels using different molecular weight PVA and borax content (boron source). Using a high ratio of high-molecular-weight PVA resulted in the cryogels exhibiting greater mechanical properties, a lower degradation rate (0.6–1.7% vs. 18–20%) and a higher borax content release (4.98 vs. 1.85, 1.08 nanomole) in contrast to their counterparts with low-molecular-weight PVA. The bioactive impacts of the released borax on cellular behaviour were investigated using MG63 cells seeded into the cryogel scaffolds. It was revealed that the borax-containing scaffolds and their extracts induced MG63 cell migration and the formation of nodule-like aggregates, whilst cryogel scaffolds without borax did not. Moreover, the degradation products of the scaffolds were analysed through the quantification of boron release by the curcumin assay. The impact on cellular response in a scratch assay confirmed that borax released by the scaffold into media (~0.4 mg/mL) induced bone cell migration, proliferation and aggregation. This study demonstrated that boron-containing three-dimensional PVA/starch–chitosan scaffolds can potentially be used within bone tissue engineering applications. Full article

Toward the development of a practical and green approach for removing phosphate from water, a monolithic cryogel based on starch and calcium silicate hydrate (Cry–CSH) was employed as a phosphate adsorbent in a continuous flow system for the first time. The influence of flow rate, initial phosphate concentration, and adsorbent height on the adsorption efficiency was investigated. As the rate of flow and the initial concentration of phosphate increased, the total quantity of adsorbed phosphate dropped; however, the performance of the column was greatly enhanced by an increase in adsorbent height. The experimental data fit the Adams–Bohart model better than the Thomas and Yoon–Nelson models at the beginning of the adsorption process. To evaluate its applicability, the continuous flow system based on the monolithic Cry–CSH column was applied for the removal of phosphate from the discharge effluent of the Patong Municipality Wastewater Treatment Plant (Phuket, Thailand), achieving an excellent total adsorption of 94.61%. Full article

A green monolithic starch cryogel was prepared and applied for the removal of methylene blue (MB) using a batch system. The influence of various experimental parameters on MB adsorption was investigated. High removal efficiency (81.58 ± 0.59%) and adsorption capacity (34.84 mg g⁻¹) were achieved. The Langmuir model better fitted the experimental data (determination coefficient (R²) = 0.9838) than the Freundlich one (R² = 0.8542), while the kinetics of MB adsorption on the cryogel followed a pseudo-second-order model. The adsorption process was spontaneous and endothermic with an activation energy of 37.8 kJ mol⁻¹ that indicated physical adsorption. The starch cryogel was used for MB removal from a wastewater sample collected from a local Batik production community enterprise in Phuket, Thailand, and a removal efficiency of 75.6% was achieved, indicating that it has a high potential as a green adsorbent for MB removal. Full article

Monolithic cryogels from starch were successfully synthesized and applied as alternative biodegradable filters for the first time. Rice flour was cross-linked with Ca²⁺ from limewater during gelatinization before being frozen and then thawed for three cycles. The resultant material was then soaked in ethanol for 3 h before incubation at 80 °C for 1 h, yielding monolithic material with interconnected pores in sizes of 51 ± 18 to 52 ± 15 µm without any need of freeze-drying. The cryogels possessed macroporous structure with specific surface areas from 1.1 to 4.3 m²g⁻¹, they could adsorb water from 599 ± 27 to 635 ± 59% of their dry weight with low swelling ratios of 6.0 ± 0.3 to 6.4 ± 0.6 g_water/g_cryogel, and could be applied as biofilters to remove suspended particles and reduce the light absorption of water sample from 25 ± 3 to 96 ± 5%. The prepared biofilters can be re-used up to three times, although they cost only USD 0.0004/piece. Complete weight loss resulted from burial in soil for 30 days, indicating environmentally friendly biodegradation and potential for environmental applications. Full article

Benzo(a)pyrene (BaP) has been recognized as a marker for the detection of carcinogenic polycyclic aromatic hydrocarbons. In this work, a novel monolithic solid-phase extraction (SPE) sorbent based on graphene oxide nanoparticles (GO) in starch-based cryogel composite (GO-Cry) was successfully prepared for BaP analysis. Rice flour and tapioca starch (gel precursors) were gelatinized in limewater (cross-linker) under alkaline conditions before addition of GO (filler) that can increase the ability to extract BaP up to 2.6-fold. BaP analysis had a linear range of 10 to 1000 µgL⁻¹ with good linearity (R² = 0.9971) and high sensitivity (4.1 ± 0.1 a.u./(µgL⁻¹)). The limit of detection and limit of quantification were 4.21 ± 0.06 and 14.04 ± 0.19 µgL⁻¹, respectively, with excellent precision (0.17 to 2.45%RSD). The accuracy in terms of recovery from spiked samples was in the range of 84 to 110% with no significant difference to a C₁₈ cartridge. GO-Cry can be reproducibly prepared with 2.8%RSD from 4 lots and can be reused at least 10 times, which not only helps reduce the analysis costs (~0.41USD per analysis), but also reduces the resultant waste to the environment. Full article

Starch recovered from an agrifood waste, pea pods, was enzymatically modified and used to prepare cryogels applied as drug carriers. The enzymatic modification of starch was performed using the laccase/(2,2,6,6-tetramethylpiperidin-1-yl)oxyl TEMPO system, at a variable molar ratio. The characterization of the ensuing starches by solution NMR spectroscopy showed partial conversion of the primary hydroxyl groups versus aldehyde and carboxyl groups and successive creation of hemiacetal and ester bonds. Enzymatically modified starch after simple freezing and lyophilization process provided stable and compact cryogels with a morphology characterized by irregular pores, as determined by atomic force (AFM) and scanning electron microscopy (SEM). The application of cryogels as carriers of active molecules was successfully evaluated by following two different approaches of loading with drugs: a) as loaded sponge, by adsorption of drug from the liquid phase; and b) as dry-loaded cryogel, from a dehydration step added to loaded cryogel from route (a). The efficiency of the two routes was studied and compared by determining the drug release profile by proton NMR studies over time. Preliminary results demonstrated that cryogels from modified starch are good candidates to act as drug delivery systems due to their stability and prolonged residence times of loaded molecules, opening promising applications in biomedical and food packaging scenarios. Full article

The production of porous materials based on starch has been explored with supercritical drying—yielding aerogel—and freeze-drying. The two drying procedures were applied on the same gelling solution of amylomaize starch pasted at 140 °C and for two concentrations (5 and 10 wt.%). After gelation and retrogradation, water from the samples to be supercritically dried was exchanged to ethanol. The resulting starch aerogel presented high specific surface area (197 m²/g). Freeze-drying was assessed by investigating the effect of the gelation, retrogradation, freezing temperature, and sublimation pressure. The resulting starch materials were macroporous, with limited specific surface area and limited mechanical integrity. Cohesive open cell foam with pore size of ~20 µm was produced by quenching the hot starch melt in liquid nitrogen. The highest specific surface area obtained with freeze-drying was 7.7 m²/g for the hot starch melt frozen at −20 °C. Full article

Manuka honey is a well-known natural material from New Zealand, considered to have properties beneficial for burn treatment. Gels created from polyvinyl alcohol (PVA) blended with natural polymers are potential burn-care dressings, combining biocompatibility with high fluid uptake. Controlled release of manuka honey from such materials is a possible strategy for improving burn healing. This work aimed to produce polyvinyl alcohol (PVA), PVA–sodium carboxymethylcellulose (PVA-CMC), PVA–gelatin (PVA-G), and PVA–starch (PVA-S) cryogels infused with honey and to characterize these materials physicochemically, morphologically, and thermally, followed by in vitro analysis of swelling capacity, degradation/weight loss, honey delivery kinetics, and possible activity against Staphylococcus aureus. The addition of honey to PVA led to many PVA crystals with defects, while PVA–starch–honey and PVA–sodium carboxymethylcellulose–honey (PVA-CMC-H) formed amorphous gels. PVA-CMC presented the highest swelling degree of all. PVA-CMC-H and PVA–gelatin–honey presented the highest swelling capacities of the honey-laden samples. Weight loss/degradation was significantly higher for samples containing honey. Layers submitted to more freeze–thawing cycles were less porous in SEM images. With the honey concentration used, samples did not inhibit S. aureus, but pure manuka honey was bactericidal and dilutions superior to 25% honey were bacteriostatic, indicating the need for higher concentrations to be more effective. Full article

Starch is the major component of cereal, pulses, and root crops. Starch consists of two kinds of glucose polymers, amylose and amylopectin. Waxy starch—with 99–100% amylopectin—has distinctive properties, which define its functionality in many food applications. In this research, a novel material was prepared through the cryogelification of waxy starch (WS) using four cycles of freezing and thawing in indirect contact with liquid nitrogen at −150 °C. Polyvinyl alcohol (PVA) was used as a reference. The cryogels were characterized using several validation methodologies: modulated differential scanning calorimetry (MDSC), scanning electron microscopy (SEM), rheology, and Fourier transform infrared (FTIR) spectroscopy with diffuse reflectance (DR). Based on the number of freeze–thaw cycles, significant changes were found (P < 0.05) showing important structural modifications as well as reorganization of the polymeric matrix. Two cryogelification cycles of the WS were enough to obtain the best structural and functional characteristics, similar to those of PVA, which has already been tested as a cryogel. From these results, it is concluded that WS has potential as a cryogel for application in food processing. Full article