The polysaccharides (PS) have been widely used as biomaterials in drug delivery, due to their excellent biocompatibility, ease of functionalization, and intrinsic biological activities. Among the various PS-based biomaterials, the self-assembled PS nanogels (NG) featuring facile preparation are attracting evergrowing interests in various biomedical applications. Specifically, NG derived from the self-assembly of natural PS well maintain both the physicochemical and biological properties of PS while avoiding the chemical modification or alteration of PS structure, representing a potent drug delivery system for various therapeutic agents. In this review, the natural PS, such as chitosan, alginate, and hyaluronan, for self-assembled NG construction and their advantages in the applications of drug delivery have been summarized. The residues, such as amine, carboxyl, and hydroxyl groups, on these PS provide multiple sites for both ionic cross-linking and metal coordination, which greatly contribute to the formation of self-assembled NG as well as the drug loading, thus enabling a wide biomedical application of PS NG, especially for drug delivery. Future developments and considerations in the clinical translation of these self-assembled PS NG have also been discussed.

Incorporation of chitosan (CS) into Bacterial nanocellulose (BNC) matrix is of great interests in biomedical field due to the advantageous properties of each material. However, the conventional strategies result in poor composite effect with low efficiency. In this study, the three-dimensional fibrillar network of BNC was utilized as a template for the first time to homogeneously disperse CS to form nanoparticles (CSNPs) in BNC matrix via ionic gelation method, to develop chitosan nanoparticles-embedded bacterial nanocellulose (CSNPs-BNC) composites. This composite method is simple and efficient, without introducing dispersants and crosslinking agents, while retaining the mechanical properties and native 3D network structure of BNC. The CSNPs-BNC composites had excellent antibacterial activity to support potential clinical application. The CSNPs-BNC composites could promote the adhesion and proliferation of Schwann cells, and demonstrate good biocompatibility both in vitro and in vivo. The results indicated that CSNPs-BNC can provide a promising candidate for biomedical applications.

Polymeric nanoparticles have emerged as a promising approach for drug delivery systems. We prepared chitosan (CS)/sodium alginate (SAL) polyelectrolyte complex nanoparticles (CS/SAL NPs) via a simple and mild ionic gelation method by adding a CS solution to a SAL solution, and investigated the effects of molecular weight of the added CS, and the SAL:CS mass ratio on the formation of the polyelectrolyte complex nanoparticles. The well-defined CS/SAL NPs with near-monodisperse particle size of about 160 nm exhibited a pH stable structure, and pH responsive properties with a negatively or positively charged surface. The so-called \"electrostatic sponge\" structure of the polyelectrolyte complex nanoparticles enhanced their drug-loading capacity towards the differently charged model drug molecules, and favored controlled release. We also found that the drug-loading capacity was influenced by the nature of the drugs and the drug-loading media, while drug release was affected by the solubility of the drugs in the drug-releasing media. The biocompatibility and biodegradability of the polyelectrolytes in the polyelectrolyte complex nanoparticles were maintained by ionic interactions. These results indicate that CS/SAL NPs can represent a useful technique for pH-responsive drug delivery systems.