Alginates are natural polymers widely used in the food industry because of their biocompatible, biodegradable character, nontoxicity and easy availability. The bioadhesive character of alginates makes them useful in the pharmaceutical industry as well. The application areas of sodium alginate-based drug delivery systems are many and these systems can be formulated as gels, matrices, membranes, nanospheres, microspheres, etc. Worldwide researchers are exploring possible applications of alginates as coating material, preparation of controlled-release drug delivery systems such as microspheres, beads, pellets, gels, fibers, membranes, etc. In the present review, such applications of alginates are discussed.

The aim of the present study was to develop single dose delivery systems based on nanotechnology for prolonged antibiotic release in a controlled manner. Five different drug-carrier ratios of ciprofloxacin hydrochloride-loaded nanoparticles of albumin, gelatin, chitosan (CS), and lipid [solid lipid nanoparticles (SLNs)] were prepared and characterized. Average particle size was found to be in the range of 73 +/- 2 to 98 +/- 44 nm for SLNs, 140 +/- 7 to 175 +/- 24 nm for albumin nanoparticles, 143 +/- 18 to 184 +/- 27 nm for gelatin nanoparticles, and 247 +/- 48 to 322 +/- 52 nm for CS nanoparticles. A drug-to-carrier ratio of 0.5:1 was preferred for CS nanoparticles having zeta potential of >20 mV and drug encapsulation of 35.01% +/- 2.66%. Similarly, 0.6:1 ratio was preferred for albumin nanoparticles with zeta potential >16 mV and drug encapsulation 48.20% +/- 3.01%. Zeta potentials of gelatin nanoparticles loaded with ciprofloxacin suggested that they were unstable and prone to flocculation. SLN with 0.25:1 drug carrier ratio showed 38.71% +/- 2.38% drug entrapment and -28 +/- 1 mV surface charge. All the nanoparticles showed sustained drug release avoiding "burst effect" of the free drugs for up to 120 h for albumin nanoparticles, 96 h for CS and gelatin nanoparticles, and 80 h for SLNs. The drug release profiles followed Higuchi model. Results suggest that CS nanoparticles and SLNs can act as promising carriers for sustained ciprofloxacin release in infective conditions.

Novel mucoadhesive chitosan microspheres were developed to explore the possibilities of non invasive delivery of insulin. The mucoadhesive chitosan microspheres were prepared by emulsifi cation method. Formulations were characterized for various physiochemical attributes, shape, surface morphology, size and size distribution, drug payload, swelling ability and mucoadhesion. Mucoadhesive chitosan microspheres bearing insulin were evaluated for in vitro drug release and in vitro drug permeation through mucosal membrane. In vivo performance was studied on blood plasma level of glucose. Glutaraldehyde cross-linked microspheres showed better reduction of blood glucose level than citric acid cross-linked microspheres. The in vivo performance of mucoadhesive microspheres showed prolonged and controlled release of drug as compared with the conventional dosage form.

In brief, the study suggests that PVA-gelatin polymeric blends are promising as ocular inserts for prolonged release of antibiotic in the eye as compared to eyedrops. Such inserts may also be therapeutically beneficial for treatment of corneal ulcers and external ocular infections.

In situ -gelling systems has the great potential in the wide areas of drug delivery. The application areas of such systems are broad and these systems can be formulated not only as gels but also as in situ gelling nanospheres, microspheres and liposomes. To overcome the drawbacks associated with conventional drug delivery systems and take advantages of both solutions and gels, such as accurate dosing, ease of administration of the former and longer precorneal residence of the latter, a newer concept of in situ gelling drug delivery systems was came in light for the first time in the early 1980s. In situ gelling systems are the polymeric solutions which can be administered in solution form and immediately undergoes sol-gel phase transition in to a viscoelastic gel upon exposure to physiological conditions (e.g. pH, temperature and ionic concentration) or application of external triggers. In situ gelling systems seems to have wide applications in ocular therapy. A lot of research is going on in this area proves the fact that in situ gelling systems can be advantageous in the ocular drug delivery. In the present review we will discuss recent researches involving application of in situ gelling polymers, their applications in the various domains of drug delivery and marketed formulations based on in situ gelling systems.