Complex hydrogel systems composed of polymers, liposomes, and cyclodextrins: implications of composition on rheological properties and aging

Signatures of Overaging in an Aqueous Dispersion of Carbopol

In this work, we study the effect of the deformation field on the physical aging behavior of an aqueous Carbopol dispersion. It is composed of soft swollen particles of gel that get deformed and acquire a polygonal shape, with flat interfaces rendering the dispersion a soft solid-like consistency as filled volume fraction approaches unity. It has been proposed that owing to release of stored elastic energy in the deformed particles, Carbopol dispersion undergoes microstructural evolution that is reminiscent of physical aging in soft glassy materials. We observe that application of moderate magnitude of oscillatory strain to Carbopol dispersion slows down its relaxation dynamics, thereby showing characteristics of overaging. On the other hand, the sufficiently high magnitude of strain makes the relaxation dynamics faster, causing rejuvenation. We also solve the soft glassy rheology model, which, when subjected to the same flow field, corroborates with experimental observations on the Carbopol dispersion. This behavior, therefore, suggests that in a system of jammed soft particles of Carbopol, the particles occupying shallow energy wells upon application of moderate strain field adjust themselves in such a manner that they predominantly occupy the deeper energy wells leading to observe the overaging dynamics.

Effects of Liposomes Contained in Thermosensitive Hydrogels as Biomaterials Useful in Neural Tissue Engineering

Advances in the generation of suitable thermosensitive hydrogels for the delivery of cells in neural tissue engineering demonstrate a delicate relationship between physical properties and capabilities to promote cell proliferation and differentiation. To improve the properties of these materials, it is possible to add liposomes for the controlled release of bioactive elements, which in turn can affect the physical and biological properties of the hydrogels. In the present investigation, different hydrogels based on Pluronic F127 have been formulated with the incorporation of chitosan and two types of liposomes of two different sizes. The rheological and thermal properties and their relation with the neurite proliferation and growth of the PC12 cell line were evaluated. Our results show that the incorporation of liposomes modifies the properties of the hydrogels dependent on the concentration of chitosan and the lipid type in the liposomes, which directly affect the capabilities of the hydrogels to promote the viability and differentiation of PC12 cells.

Recent advances on anti-HIV vaginal delivery systems development

A review of the recent outcomes regarding technologies to prevent vaginal transmission of HIV, mainly by using antiretroviral (ARV) drugs formulated as microbicides. An introduction about the HIV transmission mechanisms by the vaginal route is included, together with the recent challenges faced for development of successful microbicide products. The outcomes of clinical evaluations are mentioned, and the different formulation strategies studied to-date, with the requirements, advantages, disadvantages and limitations of each dosage-form type, are presented. Finally, the recent attempts to apply various types of nanotechnologies in order to develop advanced microbicide-products and overcome existing limitations, are discussed.

New ethanol and propylene glycol free gel formulations containing a minoxidil-methyl-β-cyclodextrin complex as promising tools for alopecia treatment

New topical totally aqueous formulations that improve the low water solubility of minoxidil and realize an adequate permeability of drug in the skin are proposed. These formulations are lacking in propylene glycol and alcohol that are the principal irritant ingredients present in minoxidil commercial solutions. In order to enhance poor water solubility of minoxidil randomly methyl-β-cyclodextrin was used, and four hydrogels such as, calcium alginate, sodium alginate, carbopol 934 and hydroxyethylcellulose were utilized to ensure a prolonged time of contact with the scalp. The inclusion complex minoxidil/methyl-β-cyclodextrin with a molar ratio 1:1 was obtained by freeze drying and evaluated by NMR, FT-IR and DSC analysis. An apparent stability constant of formed inclusion complex was calculated by phase solubility diagram and its value was 400 M(-1). The solid inclusion complex was used to prepare gel formulations with similar dose to minoxidil commercial solution. The gels were evaluated for various technological parameters including rheological behavior, in vitro drug release and ex vivo permeation through pig skin. The best performance was observed for the calcium alginate formulation.

LIPOSOMAL GELS FOR VAGINAL DELIVERY OF THE MICROBICIDE MC-1220: PREPARATION AND IN VIVO VAGINAL TOXICITY AND PHARMACOKINETICS

MC-1220 is a highly potent and selective non-nucleoside reverse transcriptase inhibitor (NNRTI) of HIV. The objective is to develop formulations for the vaginal delivery of MC-1220 and characterize them in vitro and in vivo (drug uptake, pharmacokinetics, toxicokinetics and vaginal irritation/inflammation). Due to the low aqueous solubility of MC-1220, emulsion-type and liposomal formulations of MC-1220 were developed. After rheological property adjustment (by gelling agents), the toxicity of two types of vaginal formulations of MC-1220 (emulsion [E] and liposomal [LIP] formulations) at 0.1% (E and LIP) and 0.5% (LIP) drug concentration, towards the vaginal mucosa as well as the absorption of the drug through the vaginal epithelium were investigated, after single and multiple administrations in New Zealand white NZW rabbits, for 10 days. Vaginal irritation was found to be within the acceptable range and always lower compared to the irritation caused by positive control formulation (nonoxynol-9), for all the formulation types (and concentrations evaluated). Pharmacokinetic values measured showed that the 0.1% LIP formulation was faster and better absorbed compared to the similar concentration E formulation, although most differences were not significant due to high variations. In conclusion, both types of formulations can be considered as safe for prolonged vaginal administration of MC-1220 or other drugs.