Cellulose hydrogel development from unbleached oil palm biomass pulps for dermal drug delivery

Hydrogels are an attractive platform for drug delivery to the skin. Current cellulose hydrogel developments commonly focus on readily available bleached woody cellulose. Considering the detrimental environmental impacts of bleaching reagents, unbleached non-woody biomass was proposed as an alternative. Herein, this study aims to develop hydrogel from native cellulose extracted from oil palm empty fruit bunches for dermal drug delivery with an emphasis on evaluating the effect of alkali solvent compositions on hydrogel formation. Unbleached dissolving pulps were solubilized in alkali solvents containing sodium hydroxide (NaOH) (6-8%w/v) and urea (4-6%w/v) before crosslinking. Hydrogels were loaded with ibuprofen for skin permeation studies. Light brownish hydrogels formed are aesthetically acceptable and biodegradable with low cytotoxicity. NaOH content has a dominant role over urea where thinner and deformable crosslinked network walls in a porous hydrogel structure are associated with high NaOH content. Synergistic effects (cellulose solubility: 94 %; swelling ratio: ~2800 %) were observed at 7%w/v NaOH and 4%w/v urea with low toxicity. Most hydrogels showed >80 % of ibuprofen permeated into the skin and this increased with the swelling ratio of hydrogels. Unbleached cellulose pulps have excellent potential for hydrogel fabrication with outstanding physicomechanical properties for dermal drug delivery.