Search

Silver nanoparticles (AgNPs) were synthesized by NaBH reduction and loaded in the dry-fabricated biofilm (DFBF) or the interlayer space of montmorillonite (MMT), generating AgNPs/DFBF or AgNPs/MMT composites, respectively. Use of NaBH at lower concentrations resulted in smaller the derived AgNPs, which exhibited superior antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Transmission electron microscopy images revealed conformation of AgNPs in DFBF and MMT with sizes of 20-160 and 2 nm, respectively. The results suggested that AgNPs were immobilized more firmly in MMT than in DFBF, which prevented the flocculation of AgNPs. The adsorption of AgNPs/MMT composites on DFBF resulted in the formation of AgNPs/MMT/DFBF composites, which further inhibited AgNPs migration. Furthermore, the silver release ratios of the AgNPs/DFBF, AgNPs/MMT, and AgNPs/MMT/DFBF composites were 6.7, 1.05, and 0.414% within 48 h, respectively. The minimum inhibitory concentration of silver in the medium for the AgNPs/MMT/DFBF composite against S. aureus was as low as 0.30 μg/mL; thus, AgNPs/MMT/DFBF composite films are suitable candidates for applications in sustained-release antimicrobial dressings. [ABSTRACT FROM AUTHOR]

We investigated the combined antimicrobial effect of nisin and chitosan hydrolysates (CHs) by regulating the antimicrobial reaction order of substances due to differential releasing rate from hydroxypropylmethylcellulose-modified bacterial cellulose (HBC). The minimum inhibitory concentration of nisin against Staphylococcus aureus and that of CHs against Escherichia coli were 6 IU and 200 μg/mL, respectively. Hurdle and additive effects in antimicrobial tests were observed when nisin was used 6 h before CH treatment against S. aureus; similar effects were observed when CH was used before nisin treatment against E. coli. Simultaneously combined treatment of nisin and CHs exhibited the low antimicrobial effect. HBC was then selected as the carrier for the controlled release of nisin and CHs. A 90% inhibition in the growth of S. aureus and E. coli was achieved when 30 IU-nisin-containing HBC and 62.5 μg/mL-CH-containing HBC were used simultaneously. The controlled release of nisin and CHs by using HBC minimized the interaction between nisin and CHs as well as increased the number of microbial targets. [ABSTRACT FROM AUTHOR]

To test various formulas and techniques for manufacturing dry-fabricated bio-film (DFBF) that exhibits physical properties advantageous to the use of the DFBF in wound dressings, a DFBF was fabricated by adding chitosan (Chi) and alginate (Alg) to homogenized bacterial cellulose (BC) obtained from vinegar pellicles in vinegar brewing byproducts in this study. The results revealed that the degree of oxidation in DFBF manufactured using hydrogen peroxide oxidized BC (HOBC), with 0.092% carboxyl group content, was lower than that in DFBF manufactured using periodic acid oxidized BC (POBC), but DFBF made using HOBC exhibited higher elongation, rehydration, swelling ratios, and water vapor transmission than that fabricated using POBC. A DFBF composite gel with 98.5% water content possessed appropriate fluidity for molding. After 10 min of rinsing cross-linked HOBC, 72 ppm of calcium remained in the final DFBF, which not only prevented cell toxicity but also demonstrated desirable mechanical and rehydration properties. Overall, the modified DFBF possessed a high rehydration ratio of 51.69% and could absorb and gradually release naringin by up to 80% within 24 h. This modified DFBF has the potential for exudate absorption and the controlled release of medicinal substances at the initial stage of healing when used in wound dressings. [ABSTRACT FROM AUTHOR]

The hydrolyzed gelatin peptides, obtained from the hydrolysis of Tilapia nilotica skin gelatin with alcalase and pronase E, were fractionated using an ultrafiltration system into hydrolyzed gelatin peptides-a (10 kDa membrane), hydrolyzed gelatin peptides-b1, and hydrolyzed gelatin peptides-b2 (5 kDa membrane) fractions. The highest oxygen radical absorbance capacity was observed in hydrolyzed gelatin peptides-b2, which contained more nonpolar amino acids than the other hydrolyzed gelatin peptides. Hydrolyzed gelatin peptides-b2 at a concentration of 12.5 mg/ml exhibited the highest proliferation ability and increased the expression of Type I procollagen mRNA, which indicated an enhanced collagen synthesis. Hydrolyzed gelatin peptides protected Detroit 551 cells from 2,2′-azobis(2-amidinopropane) dihydrochloride-induced oxidative damage and increased cell viability. Hydroxylpropylmethyl cellulose-modified bacterial cellulose and dried fabricated biofilm were less eligible for Detroit 551 cell proliferation than bacterial cellulose. The release of hydrolyzed gelatin peptides in bacterial cellulose film was slower than that in hydroxylpropylmethyl cellulose-modified bacterial cellulose and dried fabricated biofilm; thus, bacterial cellulose film and hydroxylpropylmethyl cellulose-modified bacterial cellulose and dried fabricated biofilm are suitable candidates for applications in delayed release type and rapid release type biofilms, respectively. [ABSTRACT FROM PUBLISHER]

Bacterial cellulose (BC) is a nanoscale and useful biomaterial with a fine fiber network and high water holding capacity. However, dried BC exhibits poor rehydration ability. The present study investigated the rehydration ability of composites of hydrolyzed gelatin peptides (HGP) and hydroxypropylmethyl cellulose-modified BC (HBC). The HGP with molecular weights <9 kDa were obtained by hydrolyzing gelatin with a combination of 1 % alcalase and 1.5 % pronase E at 50 °C for 2 h. The HGP/HBC nanocomposites exhibited higher rehydration ratios than composites prepared with gelatin. According to SEM images, gelatin and HGP successfully penetrated the cellulose network in composite films prepared using both immersion and adsorption (DA) methods. The high hydrophilic property of HGP resulted in a rehydration ratio of approximately 180 % at a HGP/HBC ratio of 4.5:1 (W/W) in DA composites. The 1 min rehydrated HGP/HBC composites possessed similar mechanical properties to the original wet type composites. Overall, results indicated that the HGP/HBC composites prepared using the DA method demonstrated the highest rehydration ability among the composite films evaluated. [ABSTRACT FROM AUTHOR]

Many studies focus on bacterial cellulose (BC) functioning as multi-function bio-resource polymers, due to its fine fiber network, biocompatibility, high water holding capacity, and high mechanical strength. However, BC exhibits poor rehydration after drying due to its high crystallinity. This study added carboxymethylcellulose (CMC) to a BC producing culture medium, which interfered with the formation of BC structure in situ. This process created a modified BC called CBC, whose mechanical strength was found weaker than BC. Scanning electron microscope (SEM) images showed that the cellulose network in CBC became denser. X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) analysis demonstrated that the addition of CMC reduced crystallinity. CBC also exhibited the highest rehydration ratio because of the lowest crystallinity at the 1.0% CMC addition level. [ABSTRACT FROM AUTHOR]

Abstract: Nano-scale bacterial cellulose (BC) provides a fine structural network; therefore, this study investigated alkaline treated BC/gelatin composites (ATBC/G) crosslinked with transglutaminase (ATBC/G/T), genipin (ATBC/G/G), or EDC (ATBC/G/E), to improve the mechanical strength and hydrophilic property of BC composites. The ATBC/G composites displayed increased gelatin content, moduli, and hardness with increased gelatin concentrations in the immersion solution. EDC most effectively improved the mechanical properties of ATBC/G composites. Gelatin entering ATBC network, fills the empty spaces and connects to the 3D structure of ATBC. The ATBC/G/E composites maintain a network structure under 10% gelatin concentrations because gelatin tightly attaches to the ATBC surface. The ATBC/G composite exhibited analogical crystal morphology of ATBC, however, increased gelatin concentrations in addition to the EDC treatment decreased crystallinity in the composites. The FTIR spectrograph of the ATBC/G composites revealed the OH groups of the composites tended to increase. Therefore, gelatin crosslinking disrupted the crystallization formed from the hydrogen bonds between cellulose molecules. Crosslinking can also enhance the rehydration ratio. [Copyright &y& Elsevier]

Abstract: Bacterial cellulose (BC) has been studied as biomedical material due to its nanoscale fiber network, biocompatibility, and high water holding capacity. However, BC exhibits a poor rehydration after drying due to its high crystallinity. In this study, hydroxypropylmethyl cellulose (HPMC) was added into a BC fermentation culture medium to interfere with the formation of BC structure in situ and create a modified BC, named HBC. Notably, mechanical strength in HBC declined. SEM images showed that, while the cellulose bundle width of HBC was enlarged, the cellulose network void in HBC shrank. X-ray diffraction and FTIR analysis revealed that the addition of HPMC reduced the crystallinity index (CrI). HBC also exhibited the highest rehydration ratio as well as the lowest crystallinity at 0.75% HPMC addition level (named 0.75%HBC). The 0.75%HBC also exhibited a higher composition ratio of EMG/BC composite and showed the improvement in water and small molecule absorption. [ABSTRACT FROM AUTHOR]

Abstract: In an attempt to obtain bacterial cellulose (BC) with improved rehydration ability, Tween 80, urea, fluorescent brightener, hydroxypropylmethyl cellulose (HPMC) and carboxymethyl cellulose (CMC) were introduced into BC fermentation medium. Measurements of the mechanical strength of the resulting BCs (TBC, UBC, FBC, HBC and CBC) showed a decline except for UBC. SEM images showed that, although the cellulose bundle widths of FBC, HBC and CBC increase, the cellulose network void in FBC grew, while those in HBC and CBC shrank. X-ray diffraction and FT-IR analysis demonstrated that the addition of HPMC and CMC reduced the degree of crystallinity in their corresponding MBCs from 70.54% to 52.23% and 45.38%, respectively. HBC and CBC also exhibited the highest rehydration ability among all MBCs as well as the lowest crystallinity. The in situ modification with HPMC and CMC during fermentation can effectively improve rehydration ability of BC by altering its network structure. [Copyright &y& Elsevier]

Abstract: Bacterial cellulose (BC) possesses excellent water holding capacity. However, increased crystallization causes a decrease in the rehydration ability of dried BC. Due to its excellent hydrophilic properties, we used gelatin and its enzymatically modified form (EMG) to prepare BC nano-composites in an attempt to enhance the rehydration abilities properties of BC. The polar peptide fraction was increased by extended hydrolysis of fish gelatin in Alcalase. Peptides smaller than 10 kDa were obtained by hydrolysis at 50 °C for 20 min. Protein contents of composites prepared by immersing BC in 5% gelatin (Gelatin/BC) or EMG (EMG/BC) solution were 81% and 92%, respectively, both of which then formed high gelatin/BC composites (HGBC). The protein content of EMG/BC was higher than that of Gelatin/BC, as compared with low gelatin/BC composites (LGBC) that were formed by immersion in a corresponding 0.5% solution. Among both HGBC and LGBC composites, EMG/BC exhibited the best rehydration abilities. Freeze-dried EMG/BC also exhibited the fastest rehydration rate and the best ability to restore wet-type composites. Composite microstructures revealed that BC was enveloped by gelatin when non-polar EMG (NPEMG) and polar EMG (PEMG) entered the BC network and adsorbed onto cellulose ribbons. The microstructure of EMG/BC contained both PEMG/BC and NPEMG/BC structures. Gelatin hydrolysates, penetrating BC networks and forming stable composites, improved the rehydration ability of dried BC. The polar functional groups of gelatin and its hydrolysates represent the key factors contributing to the hydrophilic nature of composites. [Copyright &y& Elsevier]