Silica-based microencapsulation used in topical dermatologic applications

Microencapsulation has received extensive attention because of its various applications. Since its inception in the 1940s, this technology has been used across several areas, including the chemical, food, and pharmaceutical industries. Over-the-counter skin products often contain ingredients that readily and unevenly degrade upon contact with the skin. Enclosing these substances within a silica shell can enhance their stability and better regulate their delivery onto and into the skin. Silica microencapsulation uses silica as the matrix material into which ingredients can be embedded to form microcapsules. The FDA recognizes amorphous silica as a safe inorganic excipient and recently approved two new topical therapies for the treatment of rosacea and acne. The first approved formulation uses a novel silica-based controlled vehicle delivery technology to improve the stability of two active ingredients that are normally not able to be used in the same formulation due to potential instability and drug degradation. The formulation contains 3.0% benzoyl peroxide (BPO) and 0.1% tretinoin topical cream to treat acne vulgaris in adults and pediatric patients. The second formulation contains silica microencapsulated 5.0% BPO topical cream to treat inflammatory rosacea lesions in adults. Both formulations use the same amorphous silica sol-gel microencapsulation technology to improve formulation stability and skin compatibility parameters.

[Aspects of sustainability of topical therapy]

BACKGROUND

Topical compounds are an important treatment option in dermatology. Many ingredients and packaging do not yet sufficiently fulfill sustainable criteria.

OBJECTIVES

This article aims to provide a compact overview of sustainability criteria of topical compounds and packaging.

MATERIALS AND METHODS

Based on a selective literature search and personal experience, common ingredients and packaging of topical preparations are summarized.

RESULTS

Topical preparations often contain mineral oils, acrylates, silicones and polyethylene glycols (PEG), which show poor biodegradability and may accumulate in the environment. As an alternative to these non-renewable substances, plant-based fats, oils, and waxes can be used. Biopolymers such as plant-based gum, agar-agar, pectin, and biologically produced hyaluronic acid are an alternative to plastic polymers. The environmental footprint of glass as packaging material is overestimated. Currently, plastics and aluminum may be preferable when recycled correctly.

CONCLUSION

The production of topical formulations without using mineral oils, silicones, acrylates, and PEGs is technically challenging. A sustainable packaging material that fulfills all relevant functionalities is not yet available. Packaging should meet high requirements regarding ecological, economic, and social factors. Better performance with respect to new opportunities in recycling and waste management should be incorporated. Overall, the legislative authorities should provide relevant incentives for more sustainable topical compounds and packaging.

Silicones in dermatological topical drug formulation: Overview and advances

Silicones, more specifically those of the polydimethylsiloxane type, have been widely used in the pharmaceutical industry for decades, particularly in topical applications. In the dermatological field, in addition to provide undeniable textural and sensory benefits, they can play important functions in the physicochemical properties, stability and biopharmaceutical behavior of these formulations. However, despite the notable advances that can be attributed to the family of silicones, the reputation of these compounds is quite bad. Indeed, silicones, even if they derive from sand, are synthetic compounds. Moreover, they are not biodegradable. They flow into our wastewater and oceans, accumulating in the fauna and flora. This obviously raises many concerns in the common imagination. Do silicones represent a danger for our environment? Should the human species worry about long term toxic effects? Are the claimed benefits really that important? After exploring the various applications of silicone excipients in topical dermatological formulations with a special focus on recent advances which open breathtaking prospects for dermatological applications, this paper shed light on the specific challenges involved in preparation of silicone-based drug as well as, the in vivo behavior of these polymers, the toxicological and environmental risks associated with their application.

Thiolated Silicone Oils as New Components of Protective Creams in the Prevention of Skin Diseases

This work investigates the possibility of using thiolated silicone oils as new components in protective creams and their impact on the efficacy of these products. Thiolated silicone oils were synthesized by amide bond formation between primary amino groups of poly17dimethylsiloxane-co-(3-aminopropyl)-methylsiloxane] and carboxylic groups of thiol ligand (3-mercaptopropionic acid) with carbodiimide as a coupling agent. To evaluate and compare the properties of these kinds of thiomers, three different emulsion o/w types were obtained. Emulsion E1 contained methyl silicone oil, E2 poly[dimethylsiloxane-co-(3-aminopropyl)-methylsiloxane], and E3 thiolated silicone oil (silicone-MPA), respectively. Physicochemical properties, including pH, conductivity, droplet size distribution, viscosity, and stability, were assessed. The efficacy of barrier creams in the prevention of occupational skin diseases depends on their mechanical and rheological properties. Thus, the method which imitates the spreadability conditions on the skin and how structure reconstruction takes places was performed. We also investigated textural profile, bioadhesion, protection against water and detergents, and water vapor permeability. Emulsion E3 was characterized by beneficial occlusion, spreadability, and adhesion properties. These features with prolonged residence time on the skin can make designed barrier creams more preferable for consumers.

Diagnosis and treatment of xerosis cutis - a position paper

BACKGROUND AND RATIONALE

Xerosis cutis (also referred to as xeroderma, dry skin, asteatosis) affects more than 10 million individuals in Germany. It is among the most common dermatological diagnoses and a cardinal symptom of many dermatological, internal and neurological diseases. Even though it has been established that basic skin care plays a significant role in the management of patients with xerosis cutis, there are as yet no evidence-based algorithms for diagnosis and treatment.

OBJECTIVE

The present position paper provides physicians across all specialties with a practical, symptom-based approach to the prevention, diagnosis and treatment of xerosis cutis.

METHODS

Within a structured decision-making process, a panel of experienced dermatologists first defined questions relevant to everyday clinical practice, which were then addressed by a systematic review of the literature. Based on the evidence available as well as expert consensus, diagnostic and treatment algorithms were subsequently developed and agreed upon.

RESULTS

Xerosis cutis is generally diagnosed on clinical grounds. Possible trigger factors must be avoided, and comorbidities should be adequately and specifically treated. Suitable skin care products should be chosen with a view to improving skin hydration and restoring its barrier function. They should therefore contain both rehydrating and lipid-replenishing components. The "drier" the skin appears, the greater the lipid content should be (preferably using water-in-oil formulations). The choice of ingredients is based on a patient's individual symptoms, such as scaling (e.g., urea), fissures/rhagades (e.g., urea or dexpanthenol), erythema (e.g., licochalcone A) and pruritus (e.g., polidocanol). Other factors to be considered include the site affected and patient age. Ingredients or rather combinations thereof for which there is good clinical evidence should be preferentially used. The best evidence by far is available for urea, whose efficacy in the treatment of xerosis is further enhanced by combining it with other natural moisturizing components and ceramides. The "xerosimeter" is a tool developed in an effort to facilitate patient management and for training purposes. It not only includes practical tools for diagnosis and follow-up but also a classification of ingredients and a structured treatment algorithm.

CONCLUSION

The structured symptom- and evidence-based approach proposed herein contains a road map for diagnosis and treatment of xerosis cutis. It aims to raise awareness in terms of prevention and early treatment of this condition and may thus improve quality of life and prevent potential sequelae.

Investigation of Silicone-Containing Semisolid in Situ Film-Forming Systems Using QbD Tools

The aim of our research work was to develop dermally applicable, semisolid film-forming systems (FFSs) containing silicones, which form a film on the skin in situ, with suitable mechanical properties for skin application. FFSs were developed and investigated by means of the Quality by Design (QbD) methodology. With this QbD approach, the initial risk assessment defines the critical quality attributes (CQAs), the critical material attributes (CMAs) and the critical process parameters (CPPs) to ensure the required quality. Different semisolid systems were formed with or without silicones. During the initial risk assessment, three CQAs, namely skin adhesion, film flexibility and burst strength, were found to be critical attributes, while film appearance, film integrity and the drying time of the semisolid system, were found to be medium attributes. These parameters were investigated. The initial risk assessment also showed that there are three high CMAs: the type of silicones, film-forming excipients, drying excipients, and that there was one medium CMA: viscosity-enhancing excipients. Based on our results, the silicone content had a great effect on the film-forming systems. Different silicones affected the mechanical properties of the films in varying ways, decreased the drying time and showed promising results regarding the drying mechanism.

Entirely S-Protected Thiolated Silicone: A Novel Hydrophobic Mucoadhesive and Skin Adhesive

The aim of this study was the synthesis and evaluation of an entirely S-protected thiolated silicone as novel hydrophobic mucoadhesive and skin adhesive. 2-[(2-Amino-2-carboxyethyl)disulfanyl]nicotinic acid was covalently attached to a poly(dimethylsiloxane)-graft-polyacrylate via amide bond formation. Adhesive properties were determined via the rotating cylinder method and tensile studies on porcine small intestinal mucosa besides on porcine abdominal skin. Rheological characteristics were evaluated on a cone-plate rheometer. The S-protected thiolated silicone exhibited 128 ± 18 μmol immobilized 2-mercaptonicotinic acid per gram of polymer and showed a 5.9-fold extended time of mucosal adhesion compared with the unmodified silicone on the rotating cylinder. With a 2.3-fold higher maximum detachment force and a 1.7-fold higher total work of adhesion tested on porcine small intestinal mucosa, the S-protected thiolated silicone is superior to the unmodified silicone. Furthermore, using porcine abdominal skin, a 2.4-fold higher maximum detachment force and a 4.4-fold higher total work of adhesion obtained for the S-protected thiolated silicone outlines the preferentially adhesion to skin. Triggered by N-acetyl-L-cysteine liberated thiol groups form interchain and intrachain disulfide bonds within the polymer (6.7% m/v) causing a 23.0-fold increase in dynamic viscosity (ƞ). In parallel, the elastic modulus (G') and the viscous modulus (G") increased 39.2-fold and 8.1-fold, respectively.

Skin care in nursing: A critical discussion of nursing practice and research

Skin (self-)care is part of human life from birth until death. Today many different skin care practices, preferences, traditions and routines exist in parallel. In addition, preventive and therapeutic skin care is delivered in nursing and healthcare by formal and informal caregivers. The aim of this contribution is a critical discussion about skin care in the context of professional nursing practice. An explicit skin assessment using accurate diagnostic statements is needed for clinical decision making. Special attention should be paid on high risk skin areas, which may be either too dry or too moist. From a safety perspective the protection and maintenance of skin integrity should have the highest priority. Skin cleansing is the removal of unwanted substances from the skin surface. Despite cleansing efficacy soap, other surfactants and water will inevitably always result in the destruction of the skin barrier. Thousands of products are available to hydrate, moisturize, protect and restore skin properties dependent upon their formulation and the concentration of ingredients. These products intended to left in contact with skin exhibit several actions on and in the skin interfering with skin biology. Unwanted side effects include hyper-hydration and disorganization of lipid bilayers in the stratum corneum, a dysfunctional barrier, increased susceptibility to irritants and allergies, and increases of skin surface pH. Where the skin barrier is impaired appropriate interventions, e.g. apply lipophilic products in sufficient quantity to treat dry skin or protect the skin from exposure to irritants should be provided. A key statement of this contribution is: every skin care activity matters. Every time something is placed on the skin, a functional and structural response is provoked. This response can be either desired or undesired, beneficial or harmful. The choice of all skin care interventions in nursing and healthcare practice must be based on an accurate assessment of the skin and concomitant health conditions and on a clearly defined outcome. A standardized skin care and skin care product language is needed for researchers planning and conducting clinical trials, for reviewers doing systematic reviews and evidence-base summaries, for nurses and other healthcare workers to deliver evidence-based and safe skin care.

Recent developments in silicones for topical and transdermal drug delivery

Silicones have been used in medicines, cosmetics and medical devices for over 60 years. Polydimethylsiloxanes are polymers that are typically used either as an active in oral drug products or as excipients in topical and transdermal drug products. Inherent characteristics like hydrophobicity, adhesion and aesthetics allow silicones to offer function and performance to drug products. Recent technologies like swollen crosslinked silicone elastomer blend networks, sugar siloxanes, amphiphilic resin linear polymers and silicone hybrid pressure sensitive adhesives promise potential performance advantages and improved drug delivery efficacy. This article presents a review of recent silicone material developments focusing on their function as excipients influencing drug delivery in topical and transdermal systems.

The antimicrobial peptides psoriasin (S100A7) and koebnerisin (S100A15) suppress extracellular matrix production and proliferation of human fibroblasts

BACKGROUND/AIMS

Keloids result from aberrations in the normal wound healing cascade and can lead to pruritus, contractures and pain. The underlying mechanisms of excessive scarring are not yet understood, and most therapeutic strategies remain unsatisfactory. Psoriasin (S100A7) and koebnerisin (S100A15) are released by keratinocytes during physiological wound healing. We found S100 production is markedly decreased in keloid scar tissue. The disturbed epidermal S100 expression might contribute to keloid formation; thus, we studied their effect on dermal fibroblasts and extracellular matrix (ECM) production.

METHODS

S100 peptides, ECM regulation and distribution were analysed in normal and keloid tissue by quantitative PCR (qPCR), immunoblotting and immunofluorescent staining. Isolated dermal fibroblasts were incubated with S100 proteins, and the regulation of ECM and transforming growth factor (TGF)-β was determined using qPCR. Fibroblast proliferation and viability were determined by the 5-bromo-2'-deoxyuridine assay and crystal violet assay.

RESULTS

Keloid tissue featured a pronounced expression of ECMs, such as collagen types 1 and 3, whereas the production of psoriasin and koebnerisin was markedly decreased in keloid-derived cells and keloid tissue. Both S100 proteins inhibited the expression of collagens, fibronectin-1, α-smooth-muscle actin and TGF-β by fibroblasts. Further, they also suppressed fibroblast proliferation.

CONCLUSION

Psoriasin and koebnerisin show antifibrotic effects and may lead to novel preventive and therapeutic strategies for fibroproliferative diseases.