Smart polymers have enormous potential in various applications. In particular, smart polymeric drug delivery systems have been explored as “intelligent” delivery systems able to release, at the appropriate time and site of action, entrapped drugs in response to specific physiological triggers. These polymers exhibit a non-linear response to a small stimulus leading to a macroscopic alteration in their structure/properties. The responses vary widely from swelling/contraction to disintegration. Synthesis of new polymers and crosslinkers with greater biocompatibility and better biodegradability would increase and enhance current applications. The most fascinating features of the smart polymers arise from their versatility and tunable sensitivity. The most significant weakness of all these external stimuli-sensitive polymers is slow response time. The versatility of polymer sources and their combinatorial synthesis make it possible to tune polymer sensitivity to a given stimulus within a narrow range. Development of smart polymer systems may lead to more accurate and programmable drug delivery. In this review, we discuss various mechanisms by which polymer systems are assembled in situ to form implanted devices for sustained release of therapeutic macromolecules, and we highlight various applications in the field of advanced drug delivery.

Aim:The current study was aimed to investigate the feasibility of transdermal delivery of cromolyn sodium using a novel lipid vesicular carrier, ethosomes.Materials And Methods:Ethosomes of cromolyn sodium was prepared, optimized, and characterized for vesicle shape, vesicle size and size distribution, zeta potential, entrapment efficiency, in vitro drug release, in vitro skin permeation, in vitro skin deposition and vesicle stability. Histological examination of porcine ear skin treated with optimized ethosomal formulation was performed to study the change of skin morphologies.Results:The optimized cromolyn sodium ethosomes showed reasonable entrapment efficiency (49.88±1.84%), optimum nanometric size range (133.8 ± 7.5 nm), and high zeta potential (-69.82 ± 1.2 mV). In vitro drug release studies of optimized ethosomal formulation through cellophane membrane showed an enhanced and sustained delivery of drug compared to conventional liposomes, hydroethanolic, (45% v/v) and phosphate buffer saline PBS pH 7.4 drug solutions. The optimized ethosomal formulation showed significantly-enhanced transdermal flux (18.49 ± 0.08 mg/cm2/h) across porcine ear skin as compared to liposome (1.80 ± 0.12 mg/cm2/h), hydroethanolic drug solution (4.45 ± 0.71 mg/cm2/h), and PBS pH 7.4 drug solution (1.18 ± 0.35 mg/cm2/h). Moreover, ethosomal formulation showed better skin drug deposition (10.28 ± 0.67%) and shortest lag time (0.11 ± 0.09 h) for cromolyn sodium.Conclusion:Our significant results suggest that ethosomes can be a promising tool for transdermal delivery of cromolyn sodium.

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