Biocompatible system for transdermal delivery of                                                      medicines or cosmetics

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Biocompatible and tunable delivery systems based on modified polysaccharides weredeveloped. The systems are capable to encapsulate various active agents (bothhydrophobic and hydrophilic) and deliver them into variable environments, includingenvironments in which the active agents are sparely soluble. Moreover, the systemsallow transfer of active agents via lipid biological barriers. Therefore, they werestudied for transdermal delivery.The ex-vivo studies (on human skin) of the developed delivery systems wereperformed. The systems demonstrated successful transdermal delivery of diclofenac(highly hydrophilic medicine) and insulin (large-size macromolecule) withoutcompromising the skin tissue viability. The transferred active agents were quantifiedusing Franz cell apparatus and their release kinetics was monitored. By rational modifications of natural polysaccharides, we can tune and control thepermeation capacities and release kinetics.

Results description

First, in vitro studies of the abilities of CMC-6 and CMC-12 to introduce insulininto a lipid environment were performed. For this purpose, insulin labeled with the FITC florescent probe in sunflower oil was used. The encapsulation ability of theprepared systems was measured by spectroflorimetry and confocal laser scanningmicroscopy (Figure 1). It can be seen that among all of the examined treatments, the CMC-12 nanocarrier demonstrated best performance. At the next stage, the insulincarrying biopolymers were mounted on the Franz cell apparatus and the kinetics oftheir permeation across human skin was measured (infinite dose settings). As shownin Figure 2A, the unmodified CMC had no noticeable impact and did not enhanceinsulin permeation. While CMC-6 slightly enhanced insulin permeation, a massiveincrease was obtained using CMC-12 carrier, correlating with the results observed inin vitro studies. The superior performance of CMC-12 can be attributed to a longdodecyl substituent that increases the membrane penetration ability of that carrier. Inaddition, it can be speculated that dodecyl substituted CMC-12 biopolymer facilitatesthe formation of less tightly self-assembled structures, making it a better choice forthe encapsulation of large macromolecules such as insulin.In addition, the residual insulin in donor chamber was examined and a mirrorimage was seen (Figure 2b), given further supporting to the transdermal results. Tofurther investigate the impact of the leading compound (CMC-12), a mass balanceanalysis was performed. The results shown in the lower panel of Figure 5 demonstratethe enhanced capacity of the biopolymers, less than 30% did not permeate through thestratum corneum. As fast kinetics was found together with high efficacy, thepossibility that the barrier capacity of the skin was hampered by the biopolymers wasaddressed. For this purpose, two additional skin integrity tests were used, TransEpidermal Water Loss (TEWL) and methylene blue permeation. The results shown inTable 1 depict the TEWL and methylene blue before the application of thecompounds or after 5 or 24 hr. As can be seen, the initial readings were within theexpected range. Importantly, water loss was not affected by the compound, whichimplies that the barrier function was unaltered by the different treatments. SDStreatment was used as a positive control that indeed increased water loss by almost 3-fold, confirming that this experimental setting enables to distinguish skin damage.Similarly, no detectable levels of methylene blue were found further demonstratingthe integrity of the skin samples after exposure to the biopolymer-based deliverysystem.To assess the potential of the biopolymer for efficient delivery of a precise dose, asecond transdermal evaluation was tested, but with 5-fold lower insulin level (defineddose). As can be seen in Figure 3A, at 1 hr. the system had already reached steadystate, transferring thought the dermal barrier above 85% of the amount. Thus, thebiopolymers action can be controlled and foreseen after 1 hr of application.Next, an ex vivo human skin organ culture was used to exclude the possibility ofskin damage during the transdermal delivery process. The biopolymers were topicallyapplied to the epidermal side of the skin. As expected, sodium dodecyl sulphate(SDS) markedly compromised skin viability, as seen in the MTT results (Figure 3B).However, none of the biopolymers had any negative effects on the skin, incomparison to the naïve untreated control (Figure 3C). Similar results were obtainedfrom the histological evaluations: SDS markedly disrupted the epidermal layer;whereas no morphological alterations by the media (SO) or biopolymers wererecorded. The secreted level of the irritation cytokine IL-1α was used as anindependent marker to assess the impact of the biopolymers on the skin. The results(Figure 3D) clearly showed no enhancement by the compounds. Thus, thebiopolymers were verified to be both effective and safe. The results of TEWL andmethylene blue tests combining with the skin irritation test shown in Figure 3, verifythat the observed enhanced insulin penetration is highly unlikely the result of skindamageDelivery systems based on polysaccharide benefit from biocompatibility, safetyand cost-effectiveness, since nature sourced polysaccharides are widely available. Themost important, the properties of such systems can be carefully tuned, sincepolysaccharides have well defined chemical structure of monomer units allowingpredictable rationally modified.

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