Effect of essential oils on oral halitosis treatment: a review.

Halitosis is a very common condition which may affect up to 30% of the population. In about 90% of the cases, halitosis originates in the mouth due to inadequate plaque control, periodontal disease, dry mouth, faulty restorations, and in particular due to excessive bacterial growth. Oral malodor is mainly caused by a microbial degradation of amino acids into volatile, bad-smelling gases (volatile sulfur compounds - VSCs). Management of oral malodor is directed primarily at managing and reducing the VSC-producing bacteria count as well as masking the odor. Essential oils have been used for this purpose in traditional medicine for centuries. In the present review, data on the antimicrobial activity of essential oils against relevant oral VSC-producing bacteria are compiled and compared. Additionally, other positive aspects of essential oils with regard to oral odor are considered.

Hydrophilic Ionic Liquids as Ingredients of Gel-Based Dermal Formulations.

Ionic liquids (ILs) have several properties that offer many advantages in dermal drug delivery systems. Depending on the chemical structure, ILs can be used for protection against microorganisms, to enhance skin penetration, and as a solvent. In the present work, SEPINEO™ P 600 formulations and hydroxyethylcellulose gels containing the hydrophilic ILs hexylpyridinium chloride, choline dihydrogen phosphate, and 1-ethyl-3-methylimidazolium ethyl sulfate were prepared, and the influence of the ILs on the formulation properties was evaluated. ILs were successfully incorporated into the emulsion structure, resulting in stable formulations. The antimicrobial activity of the ILs was estimated. The minimal inhibitory concentration values for hexylpyridinium chloride are about 2.5 mg/mL. The other two ILs have no antimicrobial activity. Skin penetration enhancement of caffeine, a hydrophilic model substance, was observed in the presence of hexylpyridinium chloride.

Comparative Ungual Drug Uptake Studies: Equine Hoof Membrane vs. Human Nail Plate.

Human nail diseases, mostly caused by fungal infections, are common and difficult to treat. The development and testing of new drugs and drug delivery systems for the treatment of nail diseases is often limited by the lack of human nail material for permeation studies. Animal material is frequently used, but there are only few comparative data on the human nail plate, and there is neither a standardized test design nor a nail bed analogue to study drug uptake into the nail. In this study, a new permeation device was developed for permeation studies, and the permeation behavior of three model substances on the human nail plate and a model membrane from the horse hoof was investigated. A linear correlation was found between drug uptake by the human nail plate and the uptake by the equine hoof. The developed and established permeation device is suitable for investigations of ungual drug transport and enables the use of different membrane diameters and the use of a gel-based nail bed analog. The hydrogel-based acceptor medium used ensures adequate stabilization and hydration of the nail membrane.

Salicylate-Based Ionic Liquids as Innovative Ingredients in Dermal Formulations.

The identification and characterization of novel compounds with improved functionality and safety is of great importance. Ionic liquids are potential candidates for use in dermal formulation as multifunctional components with a large variability potential. The behavior of Ionic Liquids (ILs) in aqueous solutions has an impact on their functionality in the formulation as well as on their biological activity. Therefore, the solutions of selected ILs containing salicylate anions were investigated in the present work. The alkyl chain length of the cation determined most of the studied parameters. Thus, the surface activity, the antimicrobial activity, and cytotoxicity were directly proportional to the chain length. The salicylate anion did not affect the surface activity significantly, but had an important influence on the biological activity, especially for ILs with short chain lengths. It was found that the antimicrobial activity of benzalkonium-based ILs was mainly dependent on the cation, and the minimal inhibitory concentration (MIC) values were three order of magnitude lower than those of salicylic acid. Nevertheless, the slightly lower MIC values of benzalkonium salicylate, compared to benzalkonium chloride, might indicate a synergistic effect resulting from different modes of action of the two ions. N-hexyl nicotinamide salicylate also showed a higher antimicrobial activity than salicylic acid and, at the same time, a very good skin tolerance at concentrations up to 5% w/w. Based on our investigations N-hexyl nicotinamide salicylate was identified as potential emulsifiers / co-emulsifiers with antimicrobial properties for dermal formulations.

Dermal delivery of therapeutic DNAzymes via chitosan hydrogels.

Biopharmaceutical development is progressing rapidly. It is imperative that novel drug delivery systems are designed to protect the integrity of the biopharmaceutical, and, at the same time, transport and distribute the drug efficaciously to the target site. Administration of highly specific and sensitive molecules, like therapeutic proteins or nucleic acid-based drugs, present distinct challenges. In this study, we investigate the topical drug delivery of 10-23 DNAzymes; short single-stranded oligonucleotides with RNA-cleaving properties. We developed different hydrogel formulations based on chitosan. These natural-based polymers are particularly suitable for biopharmaceuticals due to their high biocompatibility and biodegradability. We tested these hydrogels for penetration enhancement and for protective efficacy against DNAzymes degradation. Additionally, we examined the physicochemical characteristics and the storage stability of several hydrogel preparations. The formulations developed in this study demonstrate adequate antimicrobial activity, even without the addition of preservatives. A DNAse II degradation assay confirmed their ability to prevent enzymatic degradation of the oligonucleotide. The recovery of intact oligonucleotides in full thickness porcine skin samples indicated that hydrogel formulations composed of DNA/chitosan polyplexes provided satisfactory skin penetration.

Degradation and protection of DNAzymes on human skin.

DNAzymes are catalytic nucleic acid based molecules that have become a new class of active pharmaceutical ingredients (API). Until now, five DNAzymes have entered clinical trials. Two of them were tested for topical application, whereby dermally applied DNAzymes had been prone to enzymatic degradation. To protect the DNAzymes the enzymatic activity of human skin has to be examined. Therefore, the enzymatic activity of human skin was qualitatively and quantitatively analyzed. Activity similar to that of DNase II could be identified and the specific activity was determined to be 0.59Units/mg. These results were used to develop an in vitro degradation assay to screen different kinds of protective systems on human skin. The chosen protective systems consisted of biodegradable chitosans or polyethylenimine, which forms polyplexes when combined with DNAzymes. The polyplexes were characterized in terms of particle size, zeta potential, stability and degree of complexation. The screening revealed that the protective efficiency of the polyplexes depended on the polycation and the charge ratio (ξ). At a critical ξ ratio between 1.0 and 4.1 and at a maximal zeta potential, sufficient protection of the DNAzyme was achieved. The results of this study will be helpful for the development of a protective dermal drug delivery systems using polyplexes.

Development of a protective dermal drug delivery system for therapeutic DNAzymes.

RNA-cleaving DNAzymes are a potential novel class of nucleic acid-based active pharmaceutical ingredients (API). However, developing an appropriate drug delivery system (DDS) that achieves high bioavailability is challenging. Especially in a dermal application, DNAzymes have to overcome physiological barriers composed of penetration barriers and degrading enzymes. The focus of the present study was the development of a protective and penetration-enhanced dermal DDS that was tailor made for DNAzymes. DNAzyme Dz13 was used as a potential API for topical therapy against actinic keratosis. In the progress of development and selection, different preservatives, submicron emulsions (SMEs) and the physiological pH range were validated with respect to the API's integrity. A physicochemical stable SME of a pharmaceutical grade along with a high API integrity was achieved. Additionally, two developed protective systems, consisting of a liposomal formulation or chitosan-polyplexes, reduced the degradation of Dz13 in vitro. A combination of SME and polyplexes was finally validated at the skin and cellular level by in vitro model systems. Properties of penetration, degradation and distribution were determined. The result was enhanced skin penetration efficiency and increased cellular uptake with a high protective efficiency for DNAzymes due to the developed protective DDS.

Development of an insect metalloproteinase inhibitor drug carrier system for application in chronic wound infections.

OBJECTIVES: The insect metalloproteinase inhibitor (IMPI) represents the first peptide capable of inhibiting virulence-mediating microbial M4-metalloproteinases and is promising as a therapeutic. The purpose of this study was to develop a suitable drug carrier system for the IMPI drug to enable treatment of chronic wound infections. Specifically, we studied on poloxamer 407 hydrogels, examining the influence of several additives and preservatives on the rheological parameters of the hydrogels, the bioactivity and release of IMPI. METHODS: The rheological characterisation of the hydrogel was performed by oscillatory measurements. The bioactivity of IMPI was evaluated in a Casein fluoresence quenching assay. KEY FINDINGS: In this study, a suitable application form for the dermal treatment of chronic wound infections with IMPI was designed. The influences of poloxamer 407 concentration and various additives on the viscoelastic properties and preservation of a thermosensitive hydrogel were investigated. The incorporation of the precursor drug IMPI-gluthathione-s-transferase (GST) in the hydrogel had no influence on the rheological characteristics and will be released. The bioactivity of IMPI-GST is not influenced by the hydrogel and remains constant over 4 weeks of storage. CONCLUSIONS: This study reports the development of a poloxamer hydrogel as a suitable carrier system for the application of IMPI.

Ionic liquids as ingredients in topical drug delivery systems.

Because of their properties, ionic liquids (ILs) (Ranke et al.) offer many advantages in topical drug delivery systems. For example, ionic liquids can be used to increase the solubility of sparingly soluble drugs and to enhance their topical and transdermal delivery. Furthermore, ILs can be used either to synthesize active pharmaceutical ingredients or as antimicrobial ingredients. In the present work, the conventional oil-in-water (O/W) and water-in-oil (W/O) emulsions containing the hydrophilic IL [HMIM] [Cl] and the hydrophobic IL [BMIM] [PF6] were prepared, and the influence of the ILs on emulsion properties was evaluated. It was found that ILs could be successfully incorporated into the emulsion structure, resulting in stable formulations. The antimicrobial activity of ILs in the formulations was estimated, and their application as preservatives was confirmed by performing preservative efficacy tests. Evaluation of the in vitro cytotoxicity of the emulsions containing hydrophilic or hydrophobic ILs showed the low cytotoxicity of the carriers. Finally, penetration enhancement of a fluorescent dye as a model drug in the presence of ionic liquids was shown.

In line monitoring of the preparation of water-in-oil-in-water (W/O/W) type multiple emulsions via dielectric spectroscopy.

Multiple emulsions offer various applications in a wide range of fields such as pharmaceutical, cosmetics and food technology. Two features are known to yield a great influence on multiple emulsion quality and utility as encapsulation efficiency and prolonged stability. To achieve a prolonged stability, the production of the emulsions has to be observed and controlled, preferably in line. In line measurements provide available parameters in a short time frame without the need for the sample to be removed from the process stream, thereby enabling continuous process control. In this study, information about the physical state of multiple emulsions obtained from dielectric spectroscopy (DS) is evaluated for this purpose. Results from dielectric measurements performed in line during the production cycle are compared to theoretically expected results and to well established off line measurements. Thus, a first step to include the production of multiple emulsions into the process analytical technology (PAT) guidelines of the Food and Drug Administration (FDA) is achieved. DS proved to be beneficial in determining the crucial stopping criterion, which is essential in the production of multiple emulsions. The stopping of the process at a less-than-ideal point can severely lower the encapsulation efficiency and the stability, thereby lowering the quality of the emulsion. DS is also expected to provide further information about the multiple emulsion like encapsulation efficiency.

Development of drug delivery systems for the dermal application of therapeutic DNAzymes.

DNAzymes are potent novel drugs for the treatment of inflammatory diseases such as atopic dermatitis. DNAzymes represent a novel class of pharmaceuticals that fulfil a causal therapy by interruption of the inflammation cascade at its origin. There are two challenges regarding the dermal application of DNAzymes: the large molecular weight and the sensitivity to DNases as part of the natural skin flora. To overcome these limitations suitable carrier systems have to be considered. Nano-sized drug carrier systems (submicron emulsions, microemulsions) are known to improve the skin uptake of drugs due to their ability to interact with the skin's lipids. To protect the drug against degradation, the hydrophilic drug may be incorporated into the inner aqueous phase of carrier systems, such as water-in-oil-in-water multiple emulsions. In the present study various emulsions of pharmaceutical grade were produced. Their physicochemical properties were determined and the influence of preservation systems on stability was tested. Drug release and skin uptake studies using various skin conditions and experimental set-ups were conducted. Furthermore, cellular uptake was determined by flow cytometric analysis. The investigations revealed that the developed multiple emulsion is a suitable and promising drug carrier system for the topical application of DNAzyme.

Protective effect of drug delivery systems against the enzymatic degradation of dermally applied DNAzyme.

DNAzymes are a group of RNA-cleaving DNA oligonucleotides that contain a catalytic domain and represent a novel class of antisense molecules. Although single-stranded DNAzymes may represent the most effective nucleic acid drug to date, the sensitivity to nuclease degradation is challenging. Therefore, it is important to develop a drug delivery system, which protects the molecule against degradation during dermal application. In the present study, the potential protective effect, regarding the dermal application of DNAzyme, of multiple (W/O/W) emulsions, W/O emulsions, submicron emulsion and microemulsions were investigated using a HPLC method. The HPLC method enables the quantitative analysis of DNAzyme as well as the detection of degradation products. The differences between the activity of DNase I and the activity of nucleases located in the porcine skin were compared. It was found that the degradation of an aqueous solution of DNAzyme is depending on the DNase I activity as well as on the incubation time. Furthermore, the activity of neutral and acid nucleases in skin tissue was determined to be 5.2 and 14.8 U per 1 g of porcine skin tissue, respectively. Investigation of the protective character of different delivery systems revealed that formulations containing DNAzyme in the outer water phase (submicron emulsion and microemulsion) did not exhibit any form of protective effect, whereas formulations containing DNAzyme in the inner water phase (multiple emulsion and W/O emulsion) were able to prevent the DNAzyme degradation to a considerable degree. Consequently, these formulations are promising candidates for the dermal drug delivery of oligonucleotides.