Keratin-based materials represent an important and renewable source of biopolymers, since keratin is the main component of wool, feathers and horns. Moreover, keratin extracted from wool has many useful properties such as biocompatibility and biodegradability and it supports the growth and adhesion of fibroblasts and osteoblasts. Thus, keratin is expected to be applicable for biomedical uses, such as for the production of scaffolds. In order to increase its intrinsic properties, keratin extracted from wool is transformed into nanofibres through electrospinning. Electrospinning process is a low-cost and simple method to produce nanofibrous materials that have particular properties (such as high surface to volume ratio and high porosity) that make them promising candidates for several applications, such as filter membranes, cell-growth, wound dressing and drug delivery. In particular, the most suitable solvent to produce keratin nanofibres is formic acid. Unfortunately, this solvent can be inconsistent with some additives used for specific biomedical applications. The aim of this work is to produce keratin nanofibres as scaffolds for the growth of osteoblasts by doping nanofibres with nanoparticles of hydroxyapatite (HA). HA is one of the main mineral constituents of bones and it can enhance bone reconstruction and osteoblasts' growth. HA particles are not stable in acidic media, therefore water must be used as solvent. However, electrospinning keratin from water solution is not an easy task. Improved processability can be attained by blending keratin with appropriate polymers, such as polyethylene oxide (PEO). PEO is an amphiphilic, water-soluble, and non-degradable polymer with good biocompatibility and low toxicity. This polymer is often used as an ideal model for the electrospinning process because it can be electrospun without defects from aqueous solutions in a wide range of conditions. In this work, we carried out electrospinning tests with different keratin/HA water solutions and keratin/PEO/HA blends suitable for the production of composite nanofibrous scaffolds. Keratin was obtained from wool by means of a sulphitolysis extraction method. PEO powder with an average molecular weight Mv = 4 x 105 g mol-1 was dissolved in distilled water at ambient temperature for about 12 h. The keratin/PEO blend solutions were prepared at room temperature in about 12 h obtaining a total polymer concentration of 7 % w/w with a keratin/PEO weight ratio of 70:30 and adding HA nano-powder at the concentration of 10% w/w on the keratin content. After preliminary tests, the best operating conditions of the electrospinning process resulted: flow rate 0.01 ml min-1, voltage +25kV and collector distance 20 cm. Environment conditions were in the range 25-30°C of temperature and 40-50% of relative humidity. Electrospun keratin/PEO/HA nanofibres were subjected to heating treatment in an oven at 180°C for 2 hours in order to make keratin insoluble in water and remove PEO from nanofibres. The samples were put in deionized water for 24 h in order to eliminate PEO and obtain nanofibres that are made only of keratin and HA.
Electrospinning of keratin/hydroxyapatite composite nanofibre scaffolds
F Truffa Giachet;C Vineis;A Varesano;C Tonetti;DO Sanchez Ramirez;RA Carletto;G Mazzuchetti;P Stagnaro
2015
Abstract
Keratin-based materials represent an important and renewable source of biopolymers, since keratin is the main component of wool, feathers and horns. Moreover, keratin extracted from wool has many useful properties such as biocompatibility and biodegradability and it supports the growth and adhesion of fibroblasts and osteoblasts. Thus, keratin is expected to be applicable for biomedical uses, such as for the production of scaffolds. In order to increase its intrinsic properties, keratin extracted from wool is transformed into nanofibres through electrospinning. Electrospinning process is a low-cost and simple method to produce nanofibrous materials that have particular properties (such as high surface to volume ratio and high porosity) that make them promising candidates for several applications, such as filter membranes, cell-growth, wound dressing and drug delivery. In particular, the most suitable solvent to produce keratin nanofibres is formic acid. Unfortunately, this solvent can be inconsistent with some additives used for specific biomedical applications. The aim of this work is to produce keratin nanofibres as scaffolds for the growth of osteoblasts by doping nanofibres with nanoparticles of hydroxyapatite (HA). HA is one of the main mineral constituents of bones and it can enhance bone reconstruction and osteoblasts' growth. HA particles are not stable in acidic media, therefore water must be used as solvent. However, electrospinning keratin from water solution is not an easy task. Improved processability can be attained by blending keratin with appropriate polymers, such as polyethylene oxide (PEO). PEO is an amphiphilic, water-soluble, and non-degradable polymer with good biocompatibility and low toxicity. This polymer is often used as an ideal model for the electrospinning process because it can be electrospun without defects from aqueous solutions in a wide range of conditions. In this work, we carried out electrospinning tests with different keratin/HA water solutions and keratin/PEO/HA blends suitable for the production of composite nanofibrous scaffolds. Keratin was obtained from wool by means of a sulphitolysis extraction method. PEO powder with an average molecular weight Mv = 4 x 105 g mol-1 was dissolved in distilled water at ambient temperature for about 12 h. The keratin/PEO blend solutions were prepared at room temperature in about 12 h obtaining a total polymer concentration of 7 % w/w with a keratin/PEO weight ratio of 70:30 and adding HA nano-powder at the concentration of 10% w/w on the keratin content. After preliminary tests, the best operating conditions of the electrospinning process resulted: flow rate 0.01 ml min-1, voltage +25kV and collector distance 20 cm. Environment conditions were in the range 25-30°C of temperature and 40-50% of relative humidity. Electrospun keratin/PEO/HA nanofibres were subjected to heating treatment in an oven at 180°C for 2 hours in order to make keratin insoluble in water and remove PEO from nanofibres. The samples were put in deionized water for 24 h in order to eliminate PEO and obtain nanofibres that are made only of keratin and HA.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
