Evaluation of photochemically cross-linked collagen/gold nanoparticle composites as potential skin tissue scaffolds.

Collagen type I is the main structural unit in skin tissue and is therefore used preferentially in skin tissue scaffolds. However, collagen-based 3D scaffolds have weak aqueous stability and degradation profiles in their uncross-linked states and chemical cross-linking reagents arise toxicity concerns, which generally restrict the spectrum of their biomedical applicability. Here, the research goal is to photochemically cross-link collagen type I with rose bengal (RB) when subjected to green laser light and to investigate the effect of silk sericin-capped gold nanoparticles (S-AuNP) when incorporated into scaffolds on the cross-linking process and thus on the scaffold properties. All the collagen scaffolds, that is plain collagen (C), collagen/S-AuNP (C-Au), cross-linked collagen (C-RBL), and cross-linked collagen/S-AuNP (C-AuRBL) were characterized for their potential as skin tissue scaffolds. C-AuRBL group had the best thermal stability, resistance to enzymatic degradation, and more uniform pore size distribution. None of the groups had cytotoxicity (cell viability > 70%) regarding the microscopic observations and MTT cell viability assays for L929 fibroblasts. L929 fibroblasts and primary adult human epidermal keratinocytes (HEKa) were also separately seeded on C-AuRBL scaffolds and according to microscopy results, they could support the stimulation of adhesion, morphological changes, and spreading of both cells, thereby encouraging the usage of this fabrication strategy for prospective skin tissue scaffolds.

The anticancer activity of doxorubicin-loaded levan-functionalized gold nanoparticles synthesized by laser ablation.

Here, gold nanoparticles (AuNPs) were synthesized upon exposure to nano-pulsed Nd-YAG laser irradiation in de-ionized water (PLAL) and functionalized with levan polysaccharide for assessing the anticancer efficacy of doxorubicin (DOX)-conjugated levan-capped AuNPs complexes to MCF-7 breast cancer cells. According to the physicochemical test results, the increments in levan amount enhanced the colloidal stability and the drug encapsulation efficiency (DEE) significantly. For the 10L-AuNP group having the highest levan amount (10 mg/mL levan), DEE was calculated as 92.21 ± 0.56%. The lean levan, uncapped AuNPs, and 10L-AuNP were found non-cytotoxic (>80% cell viability) in the studied concentrations with 48 h MTT assays. At higher DOX loadings (25, 50, and 100 µg/mL) of 10L-AuNP, the cell viability reduced significantly compared to free DOX. Overall, these nanoparticle complexes could be proposed as potent drug delivery vehicles for cancer drugs such as DOX, as well as other drugs in the prospective studies.

Colloidal stability and biological activity evaluation of microbial exopolysaccharide levan-capped gold nanoparticles.

The main objectives of this study were to explore the suitability of the exopolysaccharide levan, biosynthesized by Bacillus subtilis, to aid in the formation of gold nanoparticles (AuNPs) and to investigate the colloidal stability and in vitro biological activity of this biopolymer-AuNPs complex. AuNPs (mainly spherical, 8-10 nm-sized, and monodispersed) were successfully synthesized in levan concentrations up to 0.5% w/v (L-AuNP0.5) while exposed to ultraviolet C (UVC) irradiation. The increase of levan quantity decreased the size of AuNPs according to Transmission Electron Microscopy (TEM) images and enhanced the colloidal stability significantly. The presence of L-AuNP0.5 at the highest treatment dose (1000 µg/mL) exhibited substantial cytotoxicity towards L-929 mouse fibroblasts for all incubation periods. Dose-dependent toxicity was observed for the first day while, after this threshold value, medium (100 µg/mL) and the lowest (10 µg/mL) treatment doses were non-cytotoxic during 7 days of incubation, implying dose and time-independent cell viabilities (> 95%) compared to the negative control (complete cell culture medium). There occurred a special surface interaction with cells and L-AuNP0.5, especially when the cells were subjected to deliberate starvation periods to increase L-AuNP0.5 internalization via passive and active endocytosis. Scanning Electron Microscopy (SEM) images showed high accumulation of L-AuNP0.5 around or inside the cell membrane after 7 days. Overall, this attribute (high uptake of L-AuNP0.5) could make them promising candidates for prospective cancer therapeutics or drug delivery systems by enabling the cell internalization of anticancer drugs.

One-pot facile synthesis of silk sericin-capped gold nanoparticles by UVC radiation: Investigation of stability, biocompatibility, and antibacterial activity.

Herein, an easy one-pot synthesis method for gold nanoparticles (AuNPs), involving only gold salt and sericin extracted from silkworm cocoon in the presence of ultraviolet C (UVC) radiation, was developed. Nanoparticle formation was confirmed by characteristic surface plasmon resonance peaks at 520-540 nm wavelengths, and the influence of silk sericin on enhancing the colloidal stability of AuNPs was confirmed. Transmission electron microscopy examination showed the average size (<10 nm) and size distribution decreased significantly with higher sericin concentration. No antibacterial activity was observed on Gram-positive Bacillus subtilis or Gram-negative Escherichia coli for sole AuNPs (0.065-0.26 mg/ml), but the conjugation of AuNPs with streptomycin antibiotic decreased significantly the required minimum inhibitory concentration doses, as also confirmed with agar plating, Scanning Electron Microscopy and Atomic Force Microscopy analyses. Furthermore, sericin-capped AuNPs showed high cell viabilities (>100%) and no sign of any detectable apoptosis or necrosis in 1-day incubation. Also, high real-time cell proliferation results of AuNPs competitive with positive control groups implied excellent in vitro biocompatibility. These results evidenced that sericin enhanced the colloidal stability of AuNPs and the biological activities of sericin-capped AuNPs reported here could render them suitable nanoscale vehicles for biomedical applications.

Collagen/gold nanoparticle nanocomposites: A potential skin wound healing biomaterial.

In this study, nanocomposite collagen scaffolds incorporating gold nanoparticles (AuNPs) were prepared for wound healing applications. Initially, dose (<20 ppm) and size (>20 nm) of AuNPs that were not cytotoxic on HaCat keratinocytes and 3T3 fibroblasts were determined. Both collagen sponges and AuNP-incorporated nanocomposites (CS-Au) were cross-linked with glutaraldehyde (CS-X and CS-AuX). Incorporation of AuNPs into cross-linked scaffolds enhanced their stability against enzymatic degradation and increased the tensile strength. Hydrolytic degradation of CS-Au group was also less than CS after seven days. Upon confirming in vitro biocompatibility of the scaffolds with cytotoxicity assays, cell attachment and proliferation tests and the in vivo efficacy for healing of full-thickness skin wounds were investigated by applying CS-X, CS-AuX or a commercial product (Matriderm®) onto defect sites and covering with Ioban® drapes. Defects were covered only with drapes for untreated control group. The wound areas were examined with histopathological and biomechanical tests after 14 days of operation. CS-AuX group was superior to untreated control and Matriderm®; it suppressed the inflammation while significantly promoting granulation tissue formation. Inflammatory reaction against CS-AuX was milder than CS-X. Neovascularization was also higher in CS-AuX than other groups, though the result was not significant. Wound closure in CS-X (76%), CS-AuX (69%), and Matriderm® (65%) were better than untreated control (45%). CS-AuX group had the highest tensile strength (significantly higher than Matriderm®) and modulus (significantly higher than Matriderm® and CS-X), indicating a faster course of dermal healing. Further studies are also needed to investigate whether higher loading of AuNPs affects these results positively in a statistically meaningful manner. Overall, their contribution to the enhancement of degradation profiles and mechanical properties, their excellent in vitro biocompatibility, and tendency to accelerate wound healing are encouraging the use of AuNPs in collagen sponges as potent skin substitutes in the future.

Evaluation of sericin/collagen membranes as prospective wound dressing biomaterial.

Sericin, a silk protein, has high potential for use in biomedical applications. In this study, wound dressing membranes of Sericin (S) and Collagen (C) were prepared by glutaraldehyde cross-linking at S/C; 2:1, 1:1, 1:2, and 0:1 weight ratios. They were stable in water for 4 weeks. However, increasing the proportion of sericin had decreasing effect on the membrane stability. Water swelling property of membranes was enhanced with sericin. The highest water swelling was obtained in 1:1 group (9.06 g/g), but increasing collagen or sericin content in the membranes had a diminishing effect. Highest water vapor transmission rate was obtained with 1:2 group (1013.80 g/m(2)/day). Oxygen permeability results showed that 1:2 (7.67 mg/L) and 2:1 (7.85 mg/L) S/C groups were better than the other groups. While sericin decreased the tensile strength and elongation of membranes, it increased modulus. Sericin also increased brittleness of membranes, but their UTS range (24.93-44.92 MPa) was still suitable for a wound dressing. Membranes were not penetrable to microorganisms. Cytotoxicity studies showed that fibroblasts and keratinocytes attached and gained their characteristic morphologies. They also proliferated on membranes significantly. After 1 week of subcutaneous implantation, a fibrous capsule formed around all membranes with an acute inflammation. Sericin containing membranes showed signs of degradation (at 2nd week), while collagen only membranes remained largely intact. Eventually, sericin containing membranes degraded in 3 weeks with moderate inflammatory response. Overall results suggest that sericin/collagen membranes would be favorable as wound dressing material when sericin ratio is less than or equal to the collagen component.