Antibacterial adhesive based on oxidized tannic acid-chitosan for rapid hemostasis

Currently, bacterial infections and bleeding interfere with wound healing, and multifunctional hydrogels with appropriate blood homeostasis, skin adhesion, and antibacterial activity are desirable. In this study, chitosan-based hydrogels were synthesized using oxidized tannic acid (OTA) and Fe3+ as cross-linkers (CS-OTA-Fe) by forming covalent, non-covalent, and metal coordination bonds between Fe3+ and OTA. Our results demonstrated that CS-OTA-Fe hydrogels showed antibacterial properties against Gram-positive bacteria (Staphylococcus aureus)and Gram-negative bacteria (Escherichia coli), low hemolysis rate (< 2 %), rapid blood clotting ability, in vitro (< 2 min), and in vivo (90 s) in mouse liver bleeding. Additionally, increasing the chitosan concentration from 3 wt% to 4.5 wt% enhanced cross-linking in the network, leading to a significant improvement in the strength (from 106 ± 8 kPa to 168 ± 12 kPa) and compressive modulus (from 50 ± 9 kPa to 102 ± 14 kPa) of hydrogels. Moreover, CS-OTA-Fe hydrogels revealed significant adhesive strength (87 ± 8 kPa) to the cow's skin tissue and cytocompatibility against L929 fibroblasts. Overall, multifunctional CS-OTA-Fe hydrogels with tunable mechanical properties, excellent tissue adhesive, self-healing ability, good cytocompatibility, and fast hemostasis and antibacterial properties could be promising candidates for biomedical applications.

Triboelectric nanogenerators based on graphene oxide coated nanocomposite fibers for biomedical applications

A high demand for green and eco-friendly triboelectric nanogenerators (TENGs) has multiplied the importance of their degradability for biomedical applications. However, the charge generation of current eco-friendly TENGs is generally limited. In this research, a flexible TENG based on a silk fibroin (SF) fibrous layer and a polycaprolactone (PCL)/graphene oxide (GO) fibrous layer was developed. Moreover, the PCL/GO layer was surface modified using various concentrations of GO (0, 1.5, 3, 6, and 9 wt%). We demonstrated that surface modification using GO nanosheets significantly improved the output of the TENG. Notably, the optimized GO modified layer resulted in a voltage of 100 V, a current of 3.15 mA [Formula: see text], and a power density of 72 mW[Formula: see text]. Moreover, a thin PCL layer applied as an encapsulation layer did not significantly modulate the performance of the TENG. Furthermore, during 28 d of soaking in a phosphate buffer solution, the proposed TENG was able to successfully generate electricity. The TENG was also proposed to be used for the electrical stimulation of PC12 cells. The results confirmed that this self-powered electrical stimulator could promote the attachment and proliferation of PC12 cells. Therefore, we have shown the potential for an eco-friendly and cost-effective TENG based on GO modified PCl/GO and silk fibrous layers to be used as a power source for biomedical applications.

Mesoporous bioactive glasses for the combined application of osteosarcoma treatment and bone regeneration

In this study, mesoporous bioactive glass (MBG) sub-micro particles were prepared through sol-gel synthesis and possessed a uniform and spherical structure with particle size of 302 ± 43 nm, a pore size of 4 nm and a high surface area of 354 m² g^-1. Alendronate (AL) is often used for the treatment of bone associated diseases, in particular osteosarcoma. However, due to the low bioavailability and high toxicity at increased doses, local and sustained release would be an ideal approach to AL delivery. Here, MBGs and aminated MBGs (AMBG) were applied as carriers for AL loading. High encapsulation efficiency of 75% and 85% and loading efficiency of 60% and 63%, for MBG and AMBG, respectively, was achieved. The release profile of AL from AMBG showed a better sustained and controlled release mechanism compared to MBG. In vitro results demonstrated the non-cytotoxic nature of both MBG and AMBG following exposure to MG63 osteoblast like cell line. AL release from MBG and AMBG, even at lower concentration, provoked decreased MG63 proliferation. The osteogenic potential of MBG and AMBG following exposure to dental pulp stem cells was evaluated using alizarin red assay.

Mesoporous and hollow hydroxyapatite nanostructured particles as a drug delivery vehicle for the local release of ibuprofen

The high risk of infection caused by implantation of orthopedic bio-metals is still a daunting challenge for surgeons as it can lead to implant failure. One approach to overcome this issue is the local release of antibacterial drug through coating on the surface of a metallic implant. One ideal carrier for this purpose is hydroxyapatite (HA) particles which are bioactive, biodegradable, biocompatible and have the potential to bond to bone. In the current study, highly crystalline mesoporous HA nanostructure particles were successfully synthesized in a low-temperature solvent process with the aid of an inorganic CaCO₃ template and then fully characterized. The specific surface area and the average size of the cavities of the nanostructured mesoporous HA particles were 85 m²/g and 20 nm, respectively. The feasibility of the prepared HA mesoporous nanostructures for drug delivery, using ibuprofen as a model drug, was also investigated. The as-prepared HA mesoporous nanostructures showed a high drug-loading capacity, as well as sustained drug release in a phosphate buffered saline (PBS) at a pH of 7.4. Overall, results show that HA mesoporous nanostructures gave great potential in bone regeneration and local delivery of either drugs or biomolecules.

Bioavailability of coated and uncoated ZnO nanoparticles to cucumber in soil with or without organic matter

There is a gap of knowledge for the fate, effects and bioavailability of coated and uncoated ZnO nanoparticles (NPs) in soil. Moreover, little is known about the effects of soil properties on effects of NPs on plants. In this study, the availability ZnO NPs in two soils with different organic matter content (one treated with cow manure (CM) and the other as untreated) was compared with their bulk particles. Results showed that coated and uncoated ZnO NPs can be more bioaccessible than their bulk counterpart and despite their more positive effects at low concentration (< 100mgkg^-1), they were more phytotoxic for plants compared to the bulk ZnO particles at high concentration (1000mgkg^-1) in the soil untreated with CM. The concentration of 1000mgkg^-1 of ZnO NPs, decreased shoot dry biomass (52%) in the soil untreated with CM but increased shoot dry biomass (35%) in CM-treated soil compared to their bulk counterpart. In general, plants in the CM-treated soil showed higher Zn concentration in their tissues compared with those in untreated soil. The difference in shoot Zn concentration between CM-treated and untreated soil for NPs treatments was more than bulk particles treatment. This different percentage at 100mgkg^-1 of bulk particles was 20.6% and for coated and uncoated NPs were 37% and 32%, respectively. Generally, the distribution of ZnO among Zn fractions in soil (exchangeable, the metal bound to carbonates, Fe-Mn oxides, organic matter and silicate minerals and the residual fraction) changed based on applied Zn concentration, Zn source and soil organic matter content. The root tip deformation under high concentration of NPs (1000mgkg^-1 treatment⁾ was observed by light microscopy in plants at the soil untreated with CM. It seems that root tip deformation is one of the specific effects of NPs which in turn inhibits plant growth and nutrients uptake by root. The transmission electron microcopy image showed the aggregation of NPs inside the plant cytoplasm and their accumulation adjacent to the cell membrane.

Fate and effect of tire rubber ash nano-particles (RANPs) in cucumber

There are growing interests on effects of nano-materials on living organisms including higher plants. No report is available on positive and negative effects of rubber ash nano-particles (RANPs) on edible plants. Recently, we reported the possibility of using waste tire rubber and rubber ash as zinc (Zn) fertilizer for plants. In this nutrient solution culture study, for the first time, root uptake and the effects of RANPs on growth and Zn, cadmium (Cd), and lead (Pb) concentration in cucumber was investigated. Various Zn levels (0, 1, 5, 25, 125mgL(-1)) were applied in the form of RANPs or ZnSO4. The root RANPs uptake was visualized by light (LA), scanning electron (SEM), and transmission electron microcopies (TEM). At all Zn levels, cucumber plants supplied with RANPs produced higher shoot and root biomass compared with those supplied with ZnSO4. In addition, the RANPs resulted in higher accumulation of Zn in cucumber tissues in comparison with ZnSO4; although phytotoxicity of Zn from ZnSO4 was greater than that from RANPs. Clear evidence of the RANPs penetration into the root cells was obtained by using SEM and TEM. Filaments of RANPs were also observed at the end of roots by LM and TEM. Further research is needed to clarify the fate of the RANPs in plant cells and their possible risks for food chain.

Cognitive impairments and neuronal injury in different brain regions of a genetic rat model of absence epilepsy

Growing numbers of evidence indicate that cognitive impairments are part of clinical profile of childhood absence epilepsy. Little is known on neuropathological changes accompanied by cognitive deficits in absence epilepsy. The aim of the present study was to investigate age-dependent neuropathological changes accompanied by learning and memory impairments in Wistar Albino Glaxo from Rijswijk (WAG/Rij) rat model of absence epilepsy. Experimental groups were divided into four groups of six rats of both WAG/Rij and Wistar strains with 2 and 6 months of age. The learning and memory performances were assessed using passive avoidance paradigm and neuropathological alterations were investigated by the evaluation of the number of dark neurons and apoptotic cells as well as the expression of caspase-3 in the neocortex, the hippocampus, and different regions of the thalamus. Results revealed a decline in learning and spatial memory of 6-month-old WAG/Rij rats compared to age-matched Wistar rats as well as 2-month-old WAG/Rij and Wistar rats. The mean number of dark neurons was significantly higher in the hippocampal CA1 and CA3 areas as well as in the laterodorsal, centromedial, and reticular thalamic nuclei and the somatosensory cortex of 6-month-old WAG/Rij rats. In addition, a higher number of apoptotic cells as well as a higher expression of caspase-3 was observed in the hippocampal CA1 and CA3 regions, the laterodorsal thalamic nucleus, and the somatosensory cortex of 6-month-old WAG/Rij rats compared to other animal groups. These results indicate significant enhancement of neuronal damage and cell death accompanied by memory deficits after seizure attacks in a rat model of absence epilepsy. Seizure-induced neuronal injury and death may underlie cognitive impairments in absence epilepsy.