The influence of preparation factors on physical characteristics of chitosan nanoparticles

Chitosan has been shown to have great potentials in various pharmaceuticals and biomedical applications, including drug delivery. Derived from chitin abundantly available in the shells of crustaceans such as crabs and shrimps, this naturally occurring polysaccharide is classified based on its molecular weight: low, medium or high. This study aimed to explore the production of chitosan nanoparticles (NP) and the influence of different factors on the physical properties of the NP produced. These factors were the concentrations of acetic acid, chitosan flakes and tripolyphosphate (TPP). The design of experiment (DoE) approach was used to determine the optimum conditions for the production of chitosan NP, with particle size (nm) and polydispersity index (PdI) being set as the responses. The chitosan flakes were solubilised in acetic acid at a specific concentration determined by the DoE before dropwise addition of TPP in an ice bath. The mixture was stirred at room temperature and subsequently centrifuged to remove the unformed materials, and then was spray-dried into powder. The size, surface charge, shape and morphology of the particles produced were characterised and infrared analysis was conducted. The results showed that the particles were spherical, slightly positively charged (ζ-potential: +2.89 at pH 7) and the infrared analysis displayed important peaks of the chitosan NP. The DoE results showed that not all combinations of parameters could produce NP; hence, determination of concentration for each parameter is essential. The equation produced by the DoE will be a useful guide to minimise error in this circumstance. In conclusion, the acetic acid and chitosan flakes concentrations were found to influence the particle size positively, whilst the increment in TPP concentration will adversely affect the particle size. Similar pattern of response was also observed for the PdI of the particles. The methods used in this study has successfully produced spherical particles, with evidence of interactions between TPP and chitosan in the NP as shown in the infrared spectrum.