The percentage collagen loss was high in skin when compared with tail. This may be due to the site of application where in the nano zinc oxide may be passed through skin due to their small size and may induce oxidative stress. Hence, we suggest that regulators and industry need to address the toxicity of nanomaterials with a realistic exposure assessment rather following conventional dose measurements following existing protocols.

In this study, we have investigated the efficacy of crosslinked polyvinyl alcohol (PVA) hydrogel as a wound dressing material, using rat as the animal model. The hydrogel was synthesized by chemical crosslinking of PVA with potassium persulphate and the crosslinking reaction parameters were optimized. The developed hydrogel was found to possess excellent mechanical properties, high water absorption capacity, gel content, and optimum water vapor transmission rate, indicating its ability to act as an effective wound dressing material. The inherent nontoxic characteristics of PVA remained unaltered after crosslinking. The in vitro diffusion studies of bovine serum albumin (BSA) as model protein, indicated a relatively slow release of protein resulting from its microencapsulation in the polymeric matrix. For in vivo studies, full‐thickness excision wounds (2 × 2 cm2) were made on the dorsal surface of rats. The hydrogel was applied on the wound and changed at regular intervals. For comparison of wound healing ability, a radiation crosslinked PVA‐based hydrogel, “HiZel” was used as a reference control. The wounds treated with PVA hydrogel healed faster as indicated by an increased rate of wound contraction (16.5 days versus 22.0 in control group). Treatment with “Hizel” led to increase in hydroxyproline in the wound tissue, whereas treatment with PVA hydrogel led to increase in both hydroxyproline as well as hexosamine. This probably provides added strength to the tissue, thereby indicating that PVA hydrogel had higher efficacy than “Hizel”. The results suggest that chemically crosslinked PVA hydrogel could be used as an effective wound dressing material. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

No abstract

As an alternative to the standard Draize eye irritation test, the potential irritancy of compounds was evaluated by observing adverse changes that occur in chorioallantoic membrane CAM) of the hen egg (HECAM) after exposure to a test chemical placed directly on the CAM. The occurrence of hemorrhage, coagulation, and lysis in response to a test compound is the basis for employing this technique to evaluate its potential for in vivo damage to mucous membrane, in particular the eye. Irritancy is scored according to the severity and speed at which damage occurs. In the present study, five different classes of pesticides were screened for irritation potential. There was good correlation between the HECAM assay and the in vivo Draize eye irritation test. The proposed HECAM assay, which reduces the requirement for laboratory animals, could be a painless alternative to the Draize test.

The skin irritation test is designed for the prediction of acute skin irritation of nanoparticles by measurement of its cytotoxic effect, as reflected in the MTT assay, on the Reconstructed Human Epidermis (RHE) model. RHE tissues are commercially available.