Chitosan is a biodegradable biopolymer and biocompatible and undergoes enzymatic degradation to non-toxic components. The main sources of chitosan are the exoskeletons of crustaceans (crab, shrimp, or lobster shells), insects, and the cell walls of fungi. Since chitosan is nontoxic, approved by Food and Drug Administration for use in medicine. Chitin is an amino polysaccharide and is abundant next to cellulose. Chitosan is extracted from chitin by enzymatic or chemical deacetylation processes. Even though chitosan can be got from abundant marine wastes, it is costly because of the tedious process involved in the extraction of this biopolymer. The properties of chitin are translucent, pliable, resilient, and tough, and occur as a tanned proteinaceous matrix. Chitin is soluble in acids like formic acid and acetic acid and has an acetyl amine group that results in stronger hydrogen bonds between the polymer chains. The deacetylation process involves hydrolysis of the acetamide groups with concentrated NaOH or KOH. The source and conditions kept throughout synthesis will determine the level of deacetylation that occurs. Tripolyphosphate, a multivalent and is capable of forming gels through ionic interactions, typically used to create chitosan nanoparticles by an ionic gelation process. This review describes various techniques for chitosan extraction and the creation of chitosan nanoparticles. Even though the ionic gelation method is most commonly used to synthesize chitosan nanoparticles, various methods are available based on the applications of chitosan nanoparticles. Ultra-small nanoparticles of chitosan can be synthesized by changing the concentration of chitosan and the volume of solvents used in these processes. The process parameters affecting the particle size, crystallinity, morphology, and properties of chitosan nanoparticles are discussed in this review.
