Valorisation of waste chicken feathers: regeneration of keratin fibre into tubular nanofibres via electrospinning.

Abstract

The poultry industry generates billions of kilograms of chicken feathers as a by-product during chicken meat processing. A large proportion of the produced feathers is disposed of by landfilling, burial or incineration, but this causes environmental concerns due to greenhouse gas emissions and land pollution. Thus beneficiation of feathers into high-value materials is desirable. In the past few decades, there has been an influx of research on fabrication of nanofibres for applications in the health care sector. This is due to nanofibrous materials' unique properties, including high surface area to volume ratio, porosity and flexibility. These properties are vitally important in the clinical health care sector as they allow nanofibres to mimic the native extracellular matrix of most human tissues and organs, including peripheral nerves. This work aimed to valorise waste chicken feathers by extracting keratin and converting it into keratin nanofibres tubes for potential application as nerve regeneration conduits. The first step was the development of a process for extraction of keratin from chicken feathers. The method was optimised by Response Surface Methodology to obtain the best extraction conditions that included sodium bisulphite, sodium dodecyl sulphate, urea, temperature and time as independent factors that affect the yield of keratin. The process was statistically analysed to evaluate the effects of each factor and the factors' interactions on the extraction. Through scientific evidence, this work discovered that temperature is the most significant factor in the extraction process, followed by reaction time, the concentration of sodium bisulphite, and concentration of sodium dodecyl sulphate. The optimisation analysis produced a new model that predicts keratin yield (up to 67.23%) from the keratin extraction process. The second step was studying electrospinnability of the extracted keratin to generate tubular keratin nanofibres for possible use as nerve conduits in nerve regeneration. The results showed that pure keratin could not be electrospun to keratin nanofibres; however, keratin blended with polyvinyl alcohol (PVA) was spun to novel keratin nanofibres tubes. As far as the author's knowledge, this is the first time that this has been demonstrated. Analysis of the nanofibres' thermal stability, chemical properties, and morphological properties showed that the increase in keratin content in keratin/PVA mixtures increases the thermal stability of keratin/PVA nanofibres conduits, and causes a decrease in nanofibres diameters and porosity. The distribution of the nanofibers diameters also narrows as keratin content increase. Nano dimensions of the fibres were confirmed by scanning electron microscopy. These results imply a possible breakthrough in plausible applications of chicken feathers keratin into the nerve regeneration space as nerve repair conduits. This innovation will benefit the clinical health care sector in saving patients' livelihood and promoting a rapid utilisation of waste chicken feathers, resulting in a cleaner and safer environment.