Table 3 Application of keratin based biomaterials in drug delivery systems

Tragacanth gum and keratin

Chicken feather

Nanogel

Nanogels with cinnamon as herbal extract and enclosed by cotton fabrics depicted antibacterial activity against both gram +ve and gram -ve bacteria. Nanogels were reported to be biocompatible. Release of cinnamon extract is reported to be concentration dependent and follows first order kinetics.

[73]

Chitosan and keratin

Chicken feather

Hydrogels

Hydrogels with keratin chitosan ratio of 3/2 displayed most efficient controlled release of two drugs viz. Rhodamine B (RB) and Bovine Serum Albumin (BSA). At 27 °C and 7.4 pH, a maximum cumulative release of 81.7% and 31.2% for RB and BSA respectively was recorded. Approximately, the attainment of equilibrium was achieved after 8 hours for RB and 44 hours for BSA.

[143]

Poly butylene succinate (PBS) and keratin

Wool, hair and nails

Nanofibers

Electrospun nanofiber mats formed with PBS and keratin by using hexafluoro isopropanol as blending solvent showed increased release rate of Rhodamine B with increase in concentration of keratin. The blend solutions of Keratin/PBS displayed non-Newtonian behaviour, with 70/30 and 30/70 ones possessing thinner mean diameter in nanofibers owing to better orientation of polymer chains under shear stress. Electrospun mats with higher PBS content had improved thermal and mechanical properties.

[44]

Lipids and keratin microparticles

Porcupine quills

Microparticles

Produced microparticles showed 29.83% antioxidant activity. Lipid coating of keratin microparticles increased antibacterial activity for about 55% against E. coli and Staphylococcus aureus. Lipid-loaded erythromycin further improved the antibacterial properties once carried on surface of keratin microparticles.

[68]

Keratin and polybutylene succinate (PBS)

Wool 

Nanofibrous mats

Ker-PBS 50-50 electrospun nanofibrous mats loaded with 23 wt.% of diclofenac released 165.2±38.3 and 307.8±24.4 μg/cm2 after 6 and 8h respectively.

[45]

KAPs (keratin-associated proteins) and KIFs (keratin intermediate filaments)

Human hair

Keratin nanoparticles

The current study revealed that KAPs/KIFs ratios directly act upon properties and structures of keratin nanoparticles. the authors observed that higher concentration of KAPs offers higher repulsive force between particles and minimizing their aggregation potential. Reversely, increase amount of KIFs offers weak repulsive force and smaller particle size and able to maximize theophylline release.

[63]

Keratin/chitosan/glucosamine sulfate (KRT/CS/GLS)

Multi-walled carbon nanotubes (MWCNTs)

Produced composites have amorphous nature with high thermal decomposition temperature of 420 °C. MTT assay revealed maximum concentration of MWCNT-GLS/CS/KRT nanocomposites showed 83% cell viability in RAW 264.7 cells.

[117]

Alginate, chitosan, and tripolyphosphate (TPP)

Chicken feathers

Microparticles

Encapsulation efficiency of 69.24% was recorded for amoxicillin in keratin and TPP microparticles with a gradual release of up to 96% in 6 hours’ time. In comparison to pure amoxicillin the drug loaded microparticles depicted increased antibacterial activity against both E. coli and S. aureus because of controlled and prolonged drug release.

[147]

β-cyclodextrin (β-CD), keratin (K), Insulin (IN) and dialdehyde glucan (DG)

Human hair

Nanoparticles

Keratin based (β-CD-K-IN-DG) NPs had high drug loading capacity (32.81%), high encapsulation efficiency of 98.52% and has the ability to protect insulin from enzymatic and acid degradation. NPs assisted in prolonging the residence time and controlled release of insulin leading to a maximum oral bioavailability of 12.27% and high hypoglycaemic effect in type 1 diabetic rats.

[134]

Xanthan/gelatin (XG) and keratin/xanthan/gelatin (KXG)

Hydrogels

Hydrogels produced by crosslinking of xanthan, gelatin with glycerol in different ratios and loaded with vitamin C. Addition of keratin with xanthan, gelatin, glycerol (1:1:2) gave water vapour transmission at the rate 4523 ± 133 g m−2 d−1, improved L929 fibroblast viability and maximized protein release. Vitamin C increased collagen synthesis in L929 fibroblasts and was released for 100 hours showing inhibition of bacterial growth.

[24]