Poly(vinyl alcohol) (PVA) hydrogel nanoparticles have been prepared by using a water-in-oil emulsion technology plus cyclic freezing-thawing process. The PVA hydrogel nanoparticles prepared by this method are suitable for protein/peptide drug delivery since formation of the hydrogel does not require crosslinking agents or other adjuvants and does not involve any residual monomer. Particularly, there is no emulsifier involved in this new method. Bovine serum albumin (BSA), as a model protein drug, is incorporated into the PVA hydrogel nanoparticles. The PVA hydrogel nanoparticles possess a skewed or log-normal size distribution. The average diameter of the PVA hydrogel nanoparticles is 675.5+/-42.7 nm. Protein drug loading efficiency in the PVA hydrogel nanoparticles is 96.2+/-3.8%. The PVA hydrogel nanoparticles swell in an aqueous solution and the swelling degree increases with the increase of temperature. In vitro release studies show that the BSA release from the nanoparticles can be prolonged to 30 h. The BSA release follows a diffusion-controlled mechanism. The number of freezing-thawing cycle and release temperature both influence BSA release rate considerably. Less freezing-thawing cycle or higher release temperature leads to faster drug release. The BSA is stable during preparation of the PVA hydrogel nanoparticles.
