Hindawi Publishing Corporation International Journal of Biomaterials Volume 2013, Article ID 146320, 9 pages http://dx.doi.org/10.1155/2013/146320 Research Article Development of Chitosan Nanoparticles as a Stable Drug Delivery System for Protein/siRNA Haliza Katas, Maria Abdul Ghafoor Raja, and Kai Leong Lam Centre for Drug Delivery Research, Faculty of Pharmacy, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia Correspondence should be addressed to Haliza Katas; haliz12@hotmail.com Received 2 May 2013; Revised 29 August 2013; Accepted 29 August 2013 Academic Editor: Traian V. Chirila Copyright © 2013 Haliza Katas et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Chitosan nanoparticles (CS NPs) exhibit good physicochemical properties as drug delivery systems. he aim of this study is to determine the modulation of preparative parameters on the physical characteristics and colloidal stability of CS NPs. CS NPs were fabricated by ionic interaction with dextran sulphate (DS) prior to determination of their storage stability. he smallest CS NPs of 353 ± 23 nm with a surface charge of +56.2 ± 1.5 mV were produced when CS and DS were mixed at pH 4 and with a DS : CS mass ratio of 0.5 : 1. An entrapment eiciency of 98% was achieved when BSA/siRNA was loaded into the nanoparticles. he results also showed that particle size and surface charge of CS NPs were slightly changed up to 2 weeks when stored at 4 ∘ C. Greater particle size and surface charge were obtained with increasing the concentration of DS. In conclusion, NPs were suiciently stable when kept at 4 ∘ C and able to carry and protect protein. 1. Introduction Endogenous peptides, protein, and oligonucleotides are among the main drugs which attract much attention because of their great potentials in treating chronic diseases [1]. However, the extreme in vivo environment of human body has always limited the therapeutic applications of these sub- stances [2, 3]. Polymeric nanoparticles have attracted much attention as delivery systems due to their ability in overcom- ing the physiological barriers and protecting and targeting the loaded substances to speciic cells [4, 5]. Naturally occurring polymers such as chitosan (CS) have been studied to form nanoparticles [6, 7]. CS is a biodegradable polysaccharide, and it is derived from deacetylation of chitin [8]. Apart from its biocompatibility, the low toxicity, hemostatic, and bacteriostatic properties also contribute to its various appli- cations in pharmaceutical ield [9–11]. Several anions have been investigated to crosslink CS like sodium sulphate [12] and dextran sulphate (DS) [13]. DS is able to modify protein and siRNA entrapment eiciency (EE) without the use of hardening agents and control the rate of drug release due to its high charge density [14]. Besides DS is a cheap material [15], it produces mechanically more stable nanoparticles com- pared to the pentasodium tripolyphosphate (TPP) [16, 17]. Several studies had reported the unique features of chitosan nanoparticles (CS NPs) using DS. However, the modulation of preparative parameters on their physical characteristics is still not fully investigated, for example, the inluence of DS steric hindrance on the electrostatic attrac- tion between CS and BSA [18]. Furthermore, the determinant of a successful drug delivery system is dependent on its physical characteristics and stability. herefore, the objectives of present study were to modulate preparative parameters to obtain nanosized particles of CS NPs and to determine their colloidal stability at diferent storage temperatures and in various suspending mediums. 2. Materials and Methods 2.1. Materials. Low molecular weight chitosan (70 kDa with the degree of deacetylation 75%–85%), acetic acid glacial, phosphate bufered saline (PBS), bovine serum albumin (BSA, 46 kDa), and Bradford reagent was purchased from Sigma-Aldrich Inc., USA. Double-stranded siRNA