Marine environment with rich biodiversity offer unlimited choice for novel biopolymers. Sulfated polysaccharides isolated from marine algae and bacteria constitute an important group in the marine-derived biomolecules and biopolymers. They possess unique structural features which can be exploited to their fullest potential in the development of new therapeutic molecules, design of nanocarriers and stimuli-responsive drug delivery systems, development of anti-aging and moisturizing creams and as molecular probes in diagnosis of cancers and cardiovascular diseases. The aim of the present review is to highlight the sources, characteristics and applications of sulfated polysaccharides and exopolysaccharides isolated from marine algae, cyanobacteria, extremophilic and halophilic bacteria. Detailed description of physicochemical properties and versatile applications of ulvan, fucoidan, galactofucan sulfate, laminarin, mauran, cyanobacterial exopolysaccharides and other lesser known exopolysaccharides of marine bacterial origin has been provided. In a nutshell, it can be concluded that sustainable exploitation of the renewable, diverse library of these unique and novel sulfated polysaccharides will unravel newer possibilities in future and will enrich the existing arsenal of biopolymers. Key words: Exopolysaccharide, marine biopolymer, molecular probe, nanocarriers, stimuli-responsive drug delivery systems, sulfated polysaccharide.

Objective: Among the various strategies employed to enhance solubility, dissolution, and bioavailability of poorly soluble drugs in vivo, formulation of solid dispersion (SD) using hydrophilic and/or water-soluble carriers with varying physicochemical characteristics seems to be a developable, economically viable and easy option. The goal of the present study was to explore the possibilities of skimmed milk (SKM)-urea (U)-crospovidone (CP) as a novel ternary mixture of carrier-hydrotrope-superdisintegrant in SD of poorly water-soluble aceclofenac (ACF). Methods: Compatibility of ACF and ternary mixture of SKM-U-CP was confirmed by FTIR spectroscopic analysis. SDs of ACF-SKM, ACF-SKM-U and ternary hydrotropic SD, and ACF-SKM-U-CP were prepared in varying ratios of 1:1–1: 5 for ACF-SKM; 1:5:0.5, 1:5:0.75, and 1:5:1 for ACF-SKM-U and 1:5:0.75:0.25–1:5:0.75:1 for ACF-SKM-U-CP by solvent evaporation technique and were characterized by their solubility enhancement (compared to pure drug) at 25°C and drug dissolution profiles in double-distilled water and phosphate buffer (pH 6.8). Results: Based on solubility enhancement data (82.10% and 44.06%) and maximum cumulative percentage drug release data (88.45% in 9 min and 76.18% in 60 s) in double-distilled water and phosphate buffer, respectively, ACF-SKM-U(1:5:0.75) was found to the best among ACF-SKM and ACF-SKM-U SDs which were used for studying the effect of adding CP as superdisintigrant. ACF: SKM: U: CP (1: 5: 0.75: 0.50) exhibited maximum solubility enhancement of 83.92% and 49.69% and cumulative percentage release of 98.55 % in 9 min and 85.67 % in 60 s in double-distilled water and buffer, respectively. Conclusion: Therefore, the novel ternary mixture of SKM-U-CP has demonstrated marginal superiority over SKM as carrier for from hydrotropic SDs of ACF.

In vitro dissolution study should ideally be designed to predict in vivo performance precisely, providing key information on the bioavailability and establishing IVIVC. Development of discriminatory in vivo predictive dissolution model and the establishment of IVIVC is difficult to achieve with BCS Class 2 drugs as they exhibit variable absorption along the GI tract owing to pH-dependent solubility, especially for Classes IIa and IIb. In this context, the biphasic dissolution model is a powerful technique for investigating the interplay between dissolution, precipitation and partitioning of various poorly soluble molecules. The dissolution test medium comprising of immiscible aqueous and organic phases enables maintenance of sink conditions and easy quantification of poorly soluble drug partitioning into the organic phase. In the review, novel efforts have been taken to provide comprehensive information on challenges associated with the establishment of IVIVC for BCS Class II drugs, various approaches being adopted for developing discriminatory in vivo predictive dissolution model, significant outcomes of studies on biphasic dissolution model to predict the in vivo dissolution behaviour of BCS Class II drugs and the problems with the use of biphasic dissolution model including the status of FDA on the same.

Pulmonary dosage forms constitute an important route of drug delivery for systemic absorption of drugs in management of respiratory diseases as well as diseases such as diabetes, migraine, osteoporosis, and cancer. Performance of different pulmonary dosage forms is greatly influenced by aerodynamic particle size distribution of inhalable particles, spray pattern, fraction of dose actually deposited on pulmonary epithelium, dissolution of active pharmaceutical ingredient and ultimately absorption across pulmonary barriers. In vitro dissolution study should be designed to predict in vivo performance precisely, providing key information on bioavailability and establishing in vitro-in vivo correlation. To obtain meaningful data from dissolution study, focus should be on composition of dissolution medium, dissolution conditions and dissolution test apparatus. For pulmonary dosage forms, selection of physiologically relevant dissolution medium, mimicking lung fluid (LF) is a challenging task. Attempts are being made to develop bio-relevant dissolution medium to overcome the limitations associated with use of conventional media lacking lung surfactant proteins, or several salts normally present in pleural fluid. Use of simulated LFs can give a better understanding of the release mechanisms and possible in vivo behavior of pulmonary dosage forms thereby enhancing the predictive capability of the dissolution testing. In the review, efforts have been taken to provide comprehensive information on composition, physicochemical characteristics and functions of physiological LF, challenges associated with the design and development of dissolution study protocol for pulmonary dosage forms, criteria for selection of an appropriate bio-relevant dissolution medium, comparative study on various reported bio-relevant dissolution media and dissolution apparatuses employed for in vitro characterization of performance of pulmonary dosage forms.