Composite Hydrogel of Poly(vinyl alcohol) Loaded by Citrus hystrix Leaf Extract, Chitosan, and Sodium Alginate with In Vitro Antibacterial and Release Test.

Citrus hystrix leaves have been used traditionally as a spice, a traditional medicine for respiratory and digestive disorders, and a remedy for bacterial infections. This study reports on the synthesis of composite hydrogels using the freeze-thaw method with poly(vinyl alcohol) (PVA) as the building block loaded by C. hystrix leaf extract (CHLE). Additionally, chitosan (CS) and sodium alginate (SA) were also loaded, respectively, to increase the antibacterial activity and to control the extract release of the composite hydrogels. The combinations of the compositions were PVA, PVA/CHLE, PVA/CHLE/CS, PVA/CHLE/SA, and PVA/CHLE/SA/CS. The internal morphology of the hydrogels shows some changes after the PVA/CHLE hydrogel was loaded by CS, SA, and SA/CS. The analysis of the Fourier transform infrared (FTIR) spectra confirmed the presence of PVA, CHLE, CS, and SA in the composite hydrogels. From the X-ray diffraction (XRD) characterization, it was shown that the composite hydrogels maintained their semicrystalline properties with decreasing crystallinity degree after being loaded by CS, SA, and SA/CS, as also supported by differential scanning calorimetry (DSC) characterization. The compressive strength of the PVA/CHLE hydrogel decreases after the loading of CS, SA, and SA/CS, so that it becomes more elastic. Despite being loaded in the composite hydrogels, the CHLE retained its antibacterial activity, as evidenced in the in vitro antibacterial test. The loading of CS succeeded in increasing the antibacterial activity of the composite hydrogels, while the loading of SA resulted in the decrease of the antibacterial activity. The release of extract from the composite hydrogels was successfully slowed down after the loading of CS, SA, and SA/CS, resulting in a controlled release following the pseudo-Fickian diffusion. The cytotoxic activity test proved that all hydrogel samples can be used safely on normal cells up to concentrations above 1000 µg/mL.

Konjac glucomannan-based hydrogels with health-promoting effects for potential edible electronics applications: A mini-review.

Konjac glucomannan (KGM), a dietary fiber hydrocolloid polysaccharide isolated from Amorphophallus konjac tubers, has potential applications in various fields. However, the use of KGM-based hydrogels has mainly focused on the food, biomedical, and water treatment industries. KGM possesses several health benefits and could be a promising candidate for use in edible electronics. This paper presents the first review of KGM-based hydrogels as edible electronics and their potential health benefits. The paper initially focuses on the health-promoting effects of KGM-based hydrogels, such as prebiotic effects, antiobesity, antioxidant, and antibacterial properties. Then, it discusses the feasible design strategies for KGM-based hydrogels as edible electronics, considering their flexibility, mechanical properties, response to stimuli, degradability aspects, their role as electronic device components, and the retention period of the devices. Finally, this review outlines future directions for developing KGM-based hydrogels for use in edible electronics.

Quartz Crystal Microbalance Coated with Polyacrylonitrile/Nickel Nanofibers for High-Performance Methanol Gas Detection.

This study describes a sensor based on quartz crystal microbalance (QCM) coated by polyacrylonitrile (PAN) nanofibers containing nickel nanoparticles for methanol gas detection. The PAN/nickel nanofibers composites were made via electrospinning and electrospray methods. The QCM sensors coated with the PAN/nickel nanofiber composite were evaluated for their sensitivities, selectivities, and stabilities. The morphologies and elemental compositions of the sensors were examined using a scanning electron microscope-energy dispersive X-ray. A Fourier Transform Infrared spectrometer was used to investigate the elemental bonds within the nanofiber composites. The QCM sensors coated with PAN/nickel nanofibers offered a high specific surface area to enhance the QCM sensing performance. They exhibited excellent sensing characteristics, including a high sensitivity of 389.8 ± 3.8 Hz/SCCM, response and recovery times of 288 and 251 s, respectively, high selectivity for methanol compared to other gases, a limit of detection (LOD) of about 1.347 SCCM, and good long-term stability. The mechanism of methanol gas adsorption by the PAN/nickel nanofibers can be attributed to intermolecular interactions, such as the Lewis acid-base reaction by PAN nanofibers and hydrogen bonding by nickel nanoparticles. The results suggest that QCM-coated PAN/nickel nanofiber composites show great potential for the design of highly sensitive and selective methanol gas sensors.

Physicochemical Characteristics and Antibacterial Activities of Freeze-Thawed Polyvinyl Alcohol/Andrographolide Hydrogels.

Andrographolide (AG) is one of the compounds in Andrographis paniculata, which has a high antibacterial activity. This paper reports the freeze-thaw method's use to synthesize polyvinyl alcohol (PVA) hydrogels loaded with AG and its characterization. From the morphological examination, the porosity of the PVA/AG hydrogel was found to increase with the increasing AG concentration. The swelling degree test revealed that the hydrogels' maximum swelling degrees were generally greater than 100%. The composite hydrogel with the highest fraction of andrographolide (PAG-4) showed greater weight loss than the hydrogel without AG (PAG-0). The molecular interaction between PVA and AG resulted in the narrowing of the band attributed to the O-H and C=O stretching bonds and the emergence of an amorphous domain in the composite hydrogels. The loading of AG disrupted the formation of hydroxyl groups in PVA and interrupted the cross-linking between PVA chains, which lead to the decrease of the compression strength and the crystallinity increased with increasing AG. The antibacterial activity of the composite hydrogel increased with increasing AG. The PAG-4 hydrogel had the highest antibacterial activity of 37.9 ± 4.6b %. Therefore, the PVA/AG hydrogel has the potential to be used as an antibacterial device.

A freeze-thaw PVA hydrogel loaded with guava leaf extract: physical and antibacterial properties.

A polyvinyl alcohol (PVA) hydrogel loaded with guava leaf extract (GLE) has potential applications as a wound dressing with good antibacterial activity. This study succeeded in fabricating a PVA hydrogel containing GLE using the freeze-thaw (FT) method. By varying the GLE concentration, we can adjust the physical properties of the hydrogel. The addition of GLE results in a decrease in cross-linking during gelation and an increase in the pore size of the hydrogels. The increase of the pore size made the swelling increase and the mechanical strength decrease. The weight loss of the hydrogel also increases because the phosphate buffer saline (PBS) dissolves the GLE. Increasing the GLE concentration caused the Fourier-transform infrared (FTIR) absorbance peaks to widen due to hydrogen bonds formed during the FT process. The crystalline phase was transformed into an amorphous phase in the PVA/GLE hydrogel based on the X-ray diffraction (XRD) spectra. The differential scanning calorimetry (DSC) characterization showed a significant decrease in the hydrogel weight over temperatures of 30-150 °C due to the evaporation of water from the hydrogel matrix. The zone of inhibition of the PVA/GLE hydrogel increased with antibacterial activity against Staphylococcus aureus of 17.93% per gram and 15.79% per gram against Pseudomonas aeruginosa.

Polyvinylpyrrolidone/cellulose acetate electrospun composite nanofibres loaded by glycerine and garlic extract with in vitro antibacterial activity and release behaviour test.

The antibacterial activity of garlic (Allium sativum) is believed to be due to its organosulfur compounds, which can supposedly be used further in biomedical applications. This paper reported the use of electrospinning to encapsulate a garlic extract and glycerine in nanofibrous mats. Polyvinylpyrrolidone (PVP) and cellulose acetate (CA) were the building blocks of the composite fibres that served as the hydrophilic matrix to encapsulate the garlic extract with glycerine added mainly to improve the mechanical characteristics of the composite fibres. The combinations of the fibres were PVP/CA, PVP/CA/garlic, PVP/CA/glycerine, and PVP/CA/glycerine/garlic. The characterizations included the morphology, chemical interaction, swelling degree, weight loss, acidity level, wettability, in vitro antibacterial test, and release behaviour test. The composite nanofibrous mats were uniform, bead-free with a size ranging from 350 nm to 900 nm. The Fourier-transform infrared spectra proved the presence of the garlic extract and glycerine in the fibres. The swelling degree test showed that the fibrous mats generally did have maximum swelling degrees above 100% except for the PVP/CA fibrous mat, whose maximum value was not achieved within 48 hours. The fibrous mat with glycerine showed generally larger weight loss compared to the fibrous mats without glycerine. The result of the contact angle measurement proved that the composite fibres are all hydrophilic with the PVP/CA/glycerine/garlic fibres being the least hydrophilic. The pH level of the fibre mats was from 3.7 to 4.0 due to the use of acetic acid. The Young's modulus and ultimate tensile strength of the mats were significantly reduced due to the presence of glycerine. The encapsulation of the garlic extract in the fibres did not eliminate the antibacterial activity of the garlic extract, as proven in the in vitro antibacterial test. The release of the garlic extract from the composite PVP/CA/glycerine/garlic fibres was found to be the largest due to the large diameter of the fibres, while the blend of PVP with CA successfully reduced the rate of release due to the insolubility of CA. We successfully encapsulated the garlic extract and glycerine in the PVP/CA nanofibrous mats with antibacterial activity.

Mangosteen pericarp extract embedded in electrospun PVP nanofiber mats: physicochemical properties and release mechanism of α-mangostin.

BACKGROUND: α-Mangostin is a major active compound of mangosteen (Garcinia mangostana L.) pericarp extract (MPE) that has potent antioxidant activity. Unfortunately, its poor aqueous solubility limits its therapeutic application. Purpose: This paper reports a promising approach to improve the clinical use of this substance through electrospinning technique. METHODS: Polyvinylpyrrolidone (PVP) was explored as a hydrophilic matrix to carry α-mangostin in MPE. Physicochemical properties of MPE:PVP nanofibers with various extract-to-polymer ratios were studied, including morphology, size, crystallinity, chemical interaction, and thermal behavior. Antioxidant activity and the release of α-mangostin, as the chemical marker of MPE, from the resulting fibers were investigated. RESULTS: It was obtained that the MPE:PVP nanofiber mats were flat, bead-free, and in a size range of 387-586 nm. Peak shifts in Fourier-transform infrared spectra of PVP in the presence of MPE suggested hydrogen bond formation between MPE and PVP. The differential scanning calorimetric study revealed a noticeable endothermic event at 119°C in MPE:PVP nanofibers, indicating vaporization of moisture residue. This confirmed hygroscopic property of PVP. The absence of crystalline peaks of MPE at 2θ of 5.99°, 11.62°, and 13.01° in the X-ray diffraction patterns of electrospun MPE:PVP nanofibers showed amorphization of MPE by PVP after being electrospun. The radical scavenging activity of MPE:PVP nanofibers exhibited lower IC50 value (55-67 µg/mL) in comparison with pure MPE (69 µg/mL). The PVP:MPE nanofibers tremendously increased the antioxidant activity of α-mangostin as well as its release rate. Applying high voltage in electrospinning process did not destroy the chemical structure of α-mangostin as indicated by retained in vitro antioxidant activity. The release rate of α-mangostin significantly increased from 35% to over 90% in 60 minutes. The release of α-mangostin from MPE:PVP nanofibers was dependent on α-mangostin concentration and particle size, as confirmed by the first-order kinetic model as well as the Hixson-Crowell kinetic model. CONCLUSION: We successfully synthesized MPE:PVP nanofiber mats with enhanced antioxidant activity and release rate, which can potentially improve the therapeutic effects offered by MPE.