Fifty-kDa hyaluronic acid upregulates some epidermal genes without changing TNF-α expression in reconstituted epidermis.

BACKGROUND: Due to its strong water binding potential, hyaluronic acid (HA) is a well-known active ingredient for cosmetic applications. However, based on its varying molecular size, skin penetration of HA may be limited. Recent studies have demonstrated that low-molecular-weight HA (LMW HA) may show a certain proinflammatory activity. We thus aimed to characterize an LMW-sized HA molecule that combines strong anti-aging abilities with efficient skin penetration but lacks potential proinflammatory effects. METHODS: Total RNA and total protein were isolated from reconstituted human epidermis following incubation with HAs of various molecular weights (20, 50, 130, 300, 800 and 1,500 kDa). Tumor necrosis factor-α expression was determined using quantitative PCR. Genomic and proteomic expression of various junctional proteins was determined using Affymetrix and common Western blotting techniques. RESULTS: LMWHA of approximately 50 kDa did not significantly alter tumor necrosis factor-α expression compared to 20-kDa HA, but revealed significantly higher skin penetration rates than larger sized HA associated with increased expression of genes and proteins known to be involved in tight junction formation and keratinocyte cohesion. CONCLUSION: LMW HA of approximately 50 kDa shows better penetration abilities than larger-sized HA. In addition, LMW HA influences the expression of various genes including those contributing to keratinocyte differentiation and formation of intercellular tight junction complexes without showing proinflammatory activity. These observations contribute to current knowledge on the effects of LMW HA on keratinocyte biology and cutaneous physiology.

Therapeutic applications of viscous and injectable poly(ortho esters).

Poly(ortho esters) (POE) are hydrophobic and bioerodible polymers that have been investigated for pharmaceutical use since the early 1970s. Among the four described generations of POE, the third (POE III) and fourth (POE IV) are promising viscous and injectable materials which have been investigated in numerous biomedical applications. POE III has been extensively studied for ophthalmic drug delivery, it presents an excellent biocompatibility and is currently being investigated as a vehicle for sustained drug delivery to treat diseases of the posterior segment of the eye. POE IV is distinguishable by a highly reproducible and controlled synthesis, a higher hydrophobicity, and an excellent biocompatibility. It is currently under development for a variety of applications, such as ocular delivery, periodontal disease treatment and applications in veterinary medicine. This review will also focus on new perspectives for this promising family of polymers, such as guided tissue regeneration, treatment of osteoarthritis, as well as peptide and protein delivery.

Optimization of a novel bioerodible device based on auto-catalyzed poly(ortho esters) for controlled delivery of tetracycline to periodontal pocket.

Local delivery of antimicrobial agents in inflamed periodontal pocket has been shown to be effective in reducing periodontopathic microorganisms. This research focuses on developing and characterizing bioerodible formulations based on auto-catalyzed poly(ortho esters) (POExLAy) for modulated release of tetracycline over 2 weeks. POExLAy are a new versatile family of POE-containing lactoyl lactyl dimers in the polymer backbone. By modifying the proportion of lactic acid in the polymer, viscous or solid materials having different degradation rate can be produced. The formulations can be either injected or placed as a solid device directly into the periodontal pocket. Tetracycline-free base incorporated into these materials was released within 10-14 days depending on polymer structure. Increase in lactic acid content in the polymer tended to increase the drug release rate and to reduce the initial lag time. Tetracycline release from such bioerodible delivery system occurs predominantly by surface erosion of the polymeric matrix, leading to kinetics which can be zero order. This periodontal drug delivery system is designed to be used as an adjunct in the treatment of periodontal diseases. Clinical studies are currently in progress.

Development and applications of injectable poly(ortho esters) for pain control and periodontal treatment.

Poly(ortho esters) with a low glass transition temperature are semi-solid materials so that therapeutic agents can be incorporated at room temperature, without the use of solvents, by a simple mixing procedure. When molecular weights are limited to < 5 kDa, such materials are directly injectable using a needle size no larger than 22 gauge. Somewhat hydrophilic polymers can be produced by using the diketene acetal 3,9-diethylidene-2,4,8,10-tetraoxaspiro[5.5]undecane and triethylene glycol (TEG), while hydrophobic materials can be produced by using the diketene acetal and 1,10-decanediol. Molecular weight can be reproducibly controlled by using an excess of the diol, or by use of an alcohol that acts as a chain-stopper. Erosion rates can be controlled by varying the amount of latent acid incorporated into the polymer backbone. Toxicology studies using the TEG polymer have been completed and have shown that the polymer is non-toxic. Toxicology studies using the decanediol polymer are underway. Development studies using the TEG polymer aimed at providing a sustained delivery of an analgesic agent to control post-surgical pain are under development and human clinical trials using the decanediol polymer for the treatment of periodontitis are also underway.

In vitro drug release from self-catalyzed poly(ortho ester): case study of 5-fluorouracil.

Self-catalyzed poly(ortho esters) are a new variation of linear poly(ortho esters) prepared by the addition of diols to the diketene acetal 3,9-diethylidene-2,4,8,10-tetraoxaspiro[5,5]undecane where dimer segments of lactic acid or glycolic acid are built into the polymer backbone. By varying the concentration of these segments, polymer erosion rate can be controlled. The present investigation describes the in vitro drug release characteristics from these new polymers. Because poly(ortho esters) have potential applications for the delivery of antifibroblastic agents for example after glaucoma-filtering surgery, the in vitro release studies were evaluated using 5-fluorouracil as the active compound. It was shown that a mole ratio of 90/10 or 80/20 diol/diol-lactate incorporated into the polymer lead to a release of 5-fluorouracil by an erosion process. Smaller amounts of diol-lactate lead to a concomitant drug release by diffusion and erosion. It was also shown that the release rate depends on the alkyl chain length of the diol in the polymer backbone but it does not depend on the drug loading.

Release of BSA from poly(ortho ester) extruded thin strands.

A solventless procedure was used where powdered polymer and micronized protein were intimately mixed and then extruded into 1 mm strands that were cut to the desired length. The polymers used were poly(ortho esters) specifically designed to allow extrusion in the neighborhood of 70 degrees C. At these temperatures many proteins maintain activity in the dry state. In vitro erosion and BSA release results indicate that after a fairly long lag-time, BSA release and polymer erosion occur concomitantly indicating an erosion-controlled process. The lag-time could be eliminated by the addition to the mixture prior to extrusion between 1 and 5 wt% poly(ethylene glycol) or its methoxy derivatives. The lag-time could also be eliminated by using an AB-block copolymer where A is poly(ortho ester) and B is poly(ethylene glycol).

Local delivery of antimicrobial agents for the treatment of periodontal diseases.

Periodontitis is an inflammatory disease of the supporting tissues of the teeth caused by groups of specific microorganisms. Aggressive forms of periodontitis can be localized or generalized. The concept that localized problem sites may be treated by local drug delivery appears attractive as the antimicrobial agent is delivered within periodontal pockets and the therapy is targeted on specific pathogenic microorganisms. Local delivery of antimicrobial agents using controlled release systems should be considered as adjunctive to mechanical debridement for the treatment of localized forms of periodontal destruction. This article reviews various types of delivery systems evaluated in practical periodontal therapy. Despite the large number of studies showing an enhanced effectiveness of local antibiotherapy, there are insufficient comparative data to support any of the local delivery system.

Formation of peptide impurities in polyester matrices during implant manufacturing.

Most peptides are susceptible, in vivo, to proteolytic degradation, and it is difficult to formulate and to deliver them without loss of biological activity. In addition, it is often desirable to release them continuously and at a controlled rate over a period of weeks or months. For these reasons, a controlled release system is suitable. Poly(lactic acid) (PLA) is a biocompatible and biodegradable material that can be used for many applications, including the design of injectable controlled release systems for pharmaceutical agents. Development of these delivery systems presents challenges in the assessment of stability, specially for peptide drugs. By means of an extrusion method, long-acting poly(lactic acid) implants containing vapreotide, a somatostatin analogue, were prepared. The nature of the main degradation product obtained after implant manufacturing was elucidated. It was found that the main peptide impurity was a lactoyl lactyl-vapreotide conjugate. Because lactide are found in small quantities in most commercially available PLA, the influence of residual lactide in the polymeric matrix, on the formation of peptide impurities during manufacturing, was specially investigated. This work demonstrates that the degree of purity of the carrier is of great importance with regard to the formation of peptide impurities.

Poly(ortho esters) - their development and some recent applications.

Poly(ortho esters) have been under development since the early 1970s and four families of such polymers have been described. Of most interest are poly(ortho ester) III and poly(ortho ester) IV. Poly(ortho ester) III is a semisolid material that has been shown to be highly biocompatible and is currently being investigated as an adjunct to glaucoma filtering surgery and other ocular applications. However, the polymerization is difficult to control and is not readily scaled up. Poly(ortho ester) IV can be easily prepared in a highly reproducible manner, is very stable provided moisture is rigorously excluded and has also been shown to be highly biocompatible. It is currently under development for a variety of applications, such as ocular delivery, protein release, post-operative pain treatment and post-operative cancer treatment.

Bioerodible injectable poly(ortho ester) for tetracycline controlled delivery to periodontal pockets: preliminary trial in humans.

The semisolid consistency of poly(ortho esters) (POEs) containing tetracycline free base allows direct injection in the periodontal pocket and shows sustained and almost constant in vitro release in phosphate buffer, pH 7.4 at 37 degrees C, for up to 14 days. Total polymer degradation concomitant with drug release was obtained. Formulations containing 10% or 20% (wt/wt) tetracycline were evaluated in a panel of 12 patients suffering from severe and recurrent periodontitis. In the first trial including 6 patients, single-rooted teeth and molar teeth with furcations were treated immediately after scaling and root planing. Patients tolerated both formulations well, experienced no pain during application, and showed no signs of irritation or discomfort during the observation period. However, retention of the formulation was minimal in this first study. An improved clinical protocol followed in the second study (stopping bleeding after scaling and root planning) prolonged the retention of the formulations in the inflamed periodontal pockets. For up to 11 days, tetracycline concentrations in the gingival crevicular fluid were higher than the minimum inhibitory concentration of tetracycline against most periodontal pathogens.

Synthesis and characterization of self-catalyzed poly(ortho-esters) based on decanediol and decanediol-lactate.

The synthesis of poly(ortho-esters) (POEs) containing lactic acid dimers in the polymer backbone for possible use in controlled drug release applications is described. These autocatalyzed POEs are prepared by the acid catalyzed condensation of 3,9-diethylidene-2,4,8,10-tetraoxaspiro(5,5)undecane with diols to produce linear polymers. The diols used were a mixture of decanediol-lactate and decanediol in various molar ratio to produce polymers with different lactic acid contents. Polymer structures were confirmed by 13C NMR, 1H NMR, and FT-IR and physico-chemical properties, such as molecular weights, glass transition temperatures and viscoelastic behavior, were also determined.