## 7 Chitosan Based Nanoparticles for Anterior Segment of Eye  
* **Corneal keratitis** Fungal keratitis is the infection that arises in the cornea due to the commonly occurring fugal species of Candida, Aspergillus, and Fusarium. The predisposing factors include prolonged use of contact lenses, ocular trauma, vegetative ocular trauma, low socioeconomic status, and poor sanitation [49]. Corneal fungal infections are rare but severe, as they cause blindness if not treated. Fungal infection of the cornea is known as keratitis, while fungal infection located at the interior of the eye is known as endophthalmitis. Amphotericin B is a leading antibiotic which has proved its efficiency as a broad-spectrum anti-fungal agent. This macrocyclic polyene antibiotic has low bioavailability when administered as a topical formulation. This is due to effective removal mechanisms like constant blinking action and tear turnover. Along with the high molecular weight of Amphotericin B, its hydrophobicity majorly limits its penetration across the corneal epithelium [50]. Chitosan is a hydrophilic biopolymer that, when grafted with poly (lactic acid), imparts hydrophobicity to the molecule, making it an efficient delivery model for a hydrophobic drug like Amphotericin B. The PLA-g-CS copolymer is reported to be formed by the protection-graft-deprotection technique which undergoes self-assembly with Amphotericin B [51]. The nanoparticle acts as an effective drug carrier system for hydrophobic drugs with improvised water solubility and mucoadhesive strength [52]. * **Corneal/Conjunctival cancer** Conjunctival/corneal squamous cell carcinoma is one of the common malignant tumors that affect the ocular surface. Recent investigations have suggested promising results using 1% 5-Fluorouracil a pyrimidine analog topically [53]. The topical dose of 5-Fluorouracil requires repeat treatment cycles and long-term follow-up in the patients. Acute and chronic side effects may occur because of the high concentration of the drug [54]. To get around these issues, the development of chitosan-based nanoparticles that are capable of forming a sustained drug delivery system with no side effects is the need of the hour. Chitosan, a cationic polymer, when reacted with sodium alginate which is an anionic polymer, can lead to the formation of a polyionic hydrogel system that aims to achieve a lower dose requirement of 5-Fluorouracil as well as prolonged release from the nanoparticle [55]. * **Dry eye syndrome or Keratoconjunctivitis sicca** Keratoconjunctivitis sicca, commonly known as dry eye syndrome, is linked to an autoimmune condition that results due to the imbalance of protective immunoregulatory and proinflammatory pathways [56]. Extensive investigations have suggested the use of cyclospor A, a local immunosuppressive agent, for treatments of kerataconjunctivitis sicca. Despite the vast investigations to incorporate the drug in collagen shields, emulsions or liposomes, significant therapeutic efficiencies have not been established. This is due to the limitation of cyclospor's slow partition rate in corneal epithelium. When the hydrophobic peptide of cyclospor A was associated with cationic chitosan polymer, a dramatic increase in the potential to deliver cyclospor A to the outer ocular surface occurred [57]. * **Bacterial conjunctivitis** Antibiotic administration is performed in multiple ocular disease conditions. Bacterial conjunctivitis, informally known as 'pink eye,' causes irritation, watering, itching, and discharge of the eye. For treating eye infections, penicillin, aminoglycos, fluoroquinolones and tetracyclines are the common class of antibiotics administered. Eye drops are always the choice of formulation for the ocular delivery because they are easy to administer and noninvasive. Nanoparticles made up of chitosan and sodium tripolyphosphate-hyaluronic acid were loaded with ceftaglime, which belongs to the class of cephalospor antibiotics that have indicated promising results [58].