Cold processed oil-in-water emulsions for dermatological purpose: formulation design and structure analysis

Sustainable Alternatives to Petroleum-Derived Excipients in Pharmaceutical Oil-in-Water Creams

Recently, vast efforts towards sustainability have been made in the pharmaceutical industry. In conventional oil-in-water (O/W) cream formulations, various petroleum-based excipients, namely mineral oil and petrolatum, are commonly used. Natural or synthetic excipients, derived from vegetable sources, were explored as alternatives to petroleum-based excipients in prototype topical creams, with 1% (w/w) lidocaine. A conventional cream comprised of petroleum-derived excipients was compared to creams containing sustainable excipients in terms of key quality and performance attributes, physicochemical properties, and formulation performance. The petrolatum-based control formulation had the highest viscosity of 248.0 Pa·s, a melting point of 42.7°C, a low separation index at 25°C of 0.031, and an IVRT flux of 52.9 µg/cm2/h. Formulation SUS-4 was the least viscous formulation at 86.9 Pa·s, had the lowest melting point of 33.6°C, the highest separation index of 0.120, and the highest IVRT flux of 139.4 µg/cm2/h. Alternatively, SUS-5 had a higher viscosity of 131.3 Pa·s, a melting point of 43.6°C, a low separation index of 0.046, and the lowest IVRT flux of 25.2 µg/cm2/h. The cumulative drug permeation after 12 h from SUS-4, SUS-5, and the control were 126.2 µg/cm2, 113.8 µg/cm2, and 108.1 µg/cm2, respectively. The composition of the oil-in-water creams had influence on physicochemical properties and drug release; however, skin permeation was not impacted. Sustainable natural or synthetic excipients in topical cream formulations were found to be suitable alternatives to petroleum-based excipients with comparable key quality attributes and performance attributes and should be considered during formulation development.

Assessing and Predicting Physical Stability of Emulsion-Based Topical Semisolid Products: A Review

The emulsion-based topical semisolid dosage forms present a high degree of complexity due to their microstructures which is apparent from their compositions comprising at least two immiscible liquid phases, often times of high viscosity. These complex microstructures are thermodynamically unstable, and the physical stability of such preparations is governed by formulation parameters such as phase volume ratio, type of emulsifiers and their concentration, HLB value of the emulsifier, as well as by process parameters such as homogenizer speed, time, temperature etc. Therefore, a detailed understanding of the microstructure in the DP and critical factors that influence the stability of emulsions is essential to ensure the quality and shelf-life of emulsion-based topical semisolid products. This review aims to provide an overview of the main strategies used to stabilize pharmaceutical emulsions contained in semisolid products and various characterization techniques and tools that have been utilized so far to evaluate their long-term stability. Accelerated physical stability assessment using dispersion analyzer tools such as an analytical centrifuge to predict the product shelf-life has been discussed. In addition, mathematical modeling for phase separation rate for non-Newtonian systems like semisolid emulsion products has also been discussed to guide formulation scientists to predict a priori stability of these products.

Investigations of Olive Oil Industry By-Products Extracts with Potential Skin Benefits in Topical Formulations

The by-products of olive oil industry are a major ecological issue due to their phenolic content, highly toxic organic load, and low pH. However, they can be recovered and reused, since their components have antioxidant, anti-inflammatory, and photoprotector properties. In this work, oil-in-water creams containing three different olive oil industry by-products extracts were produced without the use of organic solvents. First, the extracts were thoroughly characterized in vitro for cytotoxicity, inhibition of skin enzymes, and antioxidant and photoprotection capacities. Safety studies were then performed, including ocular and skin irritation tests, ecotoxicity evaluation, and in vivo Human Repeat Insult Patch Test. The results obtained in this initial characterization supported the incorporation of the extracts in the cream formulations. After preparation, the creams were characterized for their organoleptic, physicochemical, droplet size and rheological properties, and microbial contamination. The results showed that all formulations were semi-solid creams, with stable pH, compatible with the skin, without microbial contamination, and with the expected droplet size range. The rheological analysis showed shear-thinning behavior with yield stress, with the viscosity decreasing with increasing shear rate. The oscillatory results suggest that the creams have a strong network structure, being easily rubbed into the skin. Finally, compatibility, acceptability and antioxidant efficacy were evaluated in vivo, in human volunteers. No adverse reactions were observed after application of the formulations on skin and the cream with the highest concentrations of phenolic compounds showed the highest antioxidant efficiency. In conclusion, the results suggest that olive oil industry by-products extracts have valuable properties that favor their re-use in the cosmetic industry. The example presented here showed their successful incorporation into creams and their impact in these formulations' appearance, pH, and rheological performance, as well as their in vivo compatibility with skin and antioxidant efficiency.

Replacing Synthetic Ingredients by Sustainable Natural Alternatives: A Case Study Using Topical O/W Emulsions

With the increasing debate on sustainability, there is a strong market trend to formulate more sustainable products for topical application. Several studies emphasize the potential applications of natural, organic, or green chemistry-derived ingredients, but comparative studies between conventional ingredients and sustainable alternatives are lacking. This type of study is considered an excellent baseline and time-saving strategy for future studies. In addition, one of the main challenges of replacing ingredients by sustainable alternatives in topical vehicles is to maintain high-quality products. Thus, the main goal of this research study was to create a well-defined strategy supported by specific experimental data for the development of sustainable topical vehicles with high-quality standards. The study was designed to evaluate the effects of replacing conventional ingredients (e.g., hydrocarbons, silicones, and preservatives) by sustainable ones on the physical, chemical, and microbiological features of topical emulsions. Additionally, in vivo assessment studies were performed to evaluate the safety, biological efficacy, and sensorial aspects of the developed formulations. The results obtained showed that the replacement of ingredients by sustainable alternatives has an effective impact on the physicochemical and structural properties of the emulsions, mainly on their rheological behavior. However, using appropriate strategies for ingredient selection and rheological adjustment, it is possible to overcome some barriers created by the use of natural raw materials, thus developing appealing and high-quality sustainable topical vehicles.

Accelerate development of topical cream drug product using a common platform base formulation

The aim of this work was to identify stable topical platform cream formulations (placebo creams without active drug substance) using the quality attributes of cream consistency, droplet size distribution (<1 μm), and separation or instability index of <0.1 to accelerate the development of topical cream drug product. The formulations were developed with six emulsifier systems that were screened in three different solvent systems across a range of emulsifier ratios. Each formulation was characterized by microscopy, separation index, and consistency. The results showed that there are three emulsifier combination (PEG 40 stearate:GMS, S21:S2, and PEG 40 stearate:Span 60) that works well with the solvent systems. Platform cream formulations F4, F15, F33, F40, F52, F69, F77, F87, and F106 were found to meet the three criteria for a long-term stable platform cream formulation. Formulation development for topical administered drug product can be very time consuming, expensive, and resourceful in identifying a chemically and physically stable product. In early development, where it can take 1-2 years to develop a first time in human (FTIH) formulation for a new chemical entity. The use of the platform base cream formulations will expedite the early development timeline for new chemical entity by 3-6 months.

Towards the Development of Artificial Bone Grafts: Combining Synthetic Biomineralisation with 3D Printing

A synthetic technique inspired by the biomineralisation process in nacre has been previously reported to be effective in replicating the nanostructural elements of nacre in 2D chitosan hydrogel films. Here we evaluate the applicability of this synthetic biomineralisation technique, herein called the McGrath method, in replicating the flat tabular morphology of calcium carbonate and other nanostructural elements obtained when 2D chitosan hydrogel films were used, on a 3D porous chitosan hydrogel-based scaffold, hence developing 3D chitosan-calcium carbonate composites. Nozzle extrusion-based 3D printing technology was used to develop 3D porous scaffolds using chitosan hydrogel as the printing ink in a custom-designed 3D printer. The rheology of the printing ink and print parameters were optimised in order to fabricate 3D cylindrical structures with a cubic lattice-based internal structure. The effects of various dehydration techniques, including air-drying, critical point-drying and freeze-drying, on the structural integrity of the as-printed scaffolds from the nano to macroscale, were evaluated. The final 3D composite materials were characterised using scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy. The study has shown that McGrath method can be used to develop chitosan-calcium carbonate composites wherein the mineral and matrix are in intimate association with each other at the nanoscale. This process can be successfully integrated with 3D printing technology to develop 3D compartmentalised polymer-mineral composites.

Design of minocycline-containing starch nanocapsules for topical delivery

Pharmaceutical research has been focussed on developing improved delivery systems while exploring new ways of using approved excipients. The present work investigated the potential of starch nanocapsules (StNC) as a topical delivery platform for hydrophilic antimicrobial drugs using minocycline hydrochloride (MH) as a model drug. Thus, a quality by design approach was used to assess the role of different factors that affect the main pharmaceutical properties of StNC prepared using an emulsification-solvent evaporation method. Full characterisation was performed in terms of particle size, encapsulation efficiency, morphology and physical stability at 5 ± 3 °C. Results show the surfactant and lipid contents play a major role in StNC particle size distribution. The MH loading only promoted minor changes upon StNC properties. Formulations were stable without variations on physicochemical properties. All tested formulations presented a zeta-potential of +33.6 ± 6.7 mV, indicating a good physical stability and evidencing that StNC are suitable nanocarriers for topical use.

Safety assessment of starch-based personal care products: Nanocapsules and pickering emulsions

The safety profile of the ingredients used in topical dosage forms and its evaluation is an issue of utmost importance. A suitable equilibrium between safety and efficacy is crucial before promoting a dermatological product. The aim of this work was to assess the safety and biological effects of starch-based vehicles (St-BV) used in such products. The hazard, exposure and dose-response assessment were used to characterize the risk of each ingredient. The EpiSkin™ assay and human repeat insult patch tests were performed to compare the theoretical safety assessment to in vitro and in vivo data. The efficacy of the St-BV was studied using biophysical measurements in human volunteers during 28 days, showing that all ingredients and their combinations were safe for the consumer. Tissue viability determined using the EpiSkin™ testing reached values between 84.0 ± 5.0% and 98.0 ± 8.6% after application of St-BV, which were considered as non-irritant to the skin. These observations were confirmed by the in vivo studies where the St-BV did not induce any sensitization on the volunteers, being safe for human use. Moreover, St-BV increased skin hydration and microcirculation, emerging as an attractive alternative to chemical raw materials.

Development of Topical Delivery Systems for Flightless Neutralizing Antibody

Flightless I (Flii) is an actin remodeling protein important for cytoskeletal regulation and cellular processes including migration, proliferation, and adhesion. Previous studies have clearly identified Flii as a novel therapeutical target for improved wound repair and have demonstrated Flii regulation using Flii neutralizing antibodies (FnAb) in different models of wound healing in vivo. Here we describe the development of an optimized topical delivery system that can neutralize Flii activity in the epidermis. Topical delivery of FnAb is an attractive approach as it provides a convenient application, sustained release, localized effect, and reduced dosage. Three successful formulations were developed, and their physical and chemical stability examined. The in vitro release revealed prolonged and sustained release of FnAb in all the tested formulations. Additionally, penetration studies using intact porcine skin showed that FnAb penetrated the epidermis and upper papillary dermis. The penetrated FnAb significantly reduced Flii expression compared to dosed matched IgG controls. This study has successfully developed a topical delivery system for FnAb that could serve as a potential platform for future localized wound treatments.

A Quality by design (QbD) approach on starch-based nanocapsules: A promising platform for topical drug delivery

Exploring novel applications for approved excipients with a history of safe use in therapeutics is a smart strategy to obtain improved pharmaceutical products. The present study aimed at developing a novel starch-based nanoparticulate carrier system (StNC) for topical delivery of lipophilic bioactive molecules. The role of the different factors that affect the particle size distribution and zeta potential of StNC prepared by the emulsification-solvent evaporation method was assessed using a quality by design approach. An optimal formulation was selected and fully characterized in terms of molecular interactions (DSC and FTIR), morphology (TEM and AFM), as well as in vitro and in vivo biological properties, including biological sensitivity/irritation studies performed in human volunteers. Results show the surfactant and lipid contents play a major role in StNC particle size distribution. In addition, all tested formulations presented a zeta potential of ca. +33.6±6.7 mV, indicating a good physical stability, while revealing an excellent compromise between stability, safety and cosmeticity, evidencing that StNC are suitable nanocarriers for topical use. Finally, the design planning methodology has clearly shown its usefulness for optimizing the formulation, being also crucial for the understanding of StNC formation process. The StNC proved to be a promising formulation strategy and a potential nanocarrier for topical lipophilic bioactive molecules.

Topical gels of etofenamate: in vitro and in vivo evaluation

Non-steroid anti-inflammatory drugs (NSAIDs), such as etofenamate, are among the most prescribed drugs used for their analgesic, anti-rheumatic, antipyretic and anti-inflammatory properties. Topical formulations have the main advantage of targeted delivery. However, drugs must overcome the skin due to its role as a physical and chemical barrier against the penetration of chemicals and microorganisms. This barrier must be altered to allow the permeation of drugs at a suitable rate to the desired site of activity. Permeation modulators can intercalate the skin outer layers causing structure disruption, opening an energetically favourable route for the drug to diffuse through. The aim of this work was the development of hydroalcoholic gels containing 5.0% (w/w) of etofenamate for topical administration with anti-inflammatory activity and enhanced drug delivery. The physical and chemical characterization, in vitro release and permeation studies and in vivo anti-inflammatory activity were assessed. The gel with 30% ethanol showed in vivo anti-inflammatory activity with suitable physical chemical and microbiologic characteristics. In vitro release and permeation studies revealed that the different amounts of ethanol used influenced the release profiles of etofenamate. Moreover, it was demonstrated that this formulation is an adequate vehicle for the etofenamate skin permeation.

Mometasone furoate-loaded cold processed oil-in-water emulsions: in vitro and in vivo studies

Over the years, research has focused on strategies to increase benefit/risk ratio of corticoids. However, vehicles intended for topical glucocorticoids delivery with an improved benefit/risk ratio are still on demand. The aim of this work was the in vitro and in vivo characterization of cold processed oil-in-water (o/w) emulsions intended for mometasone furoate (MF) delivery to induce drug targeting to upper skin strata, decreasing adverse effects. Two o/w emulsions, containing 0.1% of MF, were developed differing in the glycol used (2-methyl-2,4-pentanediol - PT and ethoxydiglycol - TC emulsions). In vitro permeation studies revealed that these emulsions are suitable vehicles for the delivery of MF containing ingredients which are responsible for a drastically increased on the permeability coefficients of MF from a theoretical value of 1.18 × 10(-4 )cm/h to 5.20 × 10(-4) ± 2.05 × 10(-4 )cm/h and 6.30 × 10(-4) ± 2.94 × 10(-4 )cm/h, for PT and TC, respectively. The tape stripping results showed that the amount of drug that reached the viable skin layers was very low (1.99 %) and the amount that remained in the stratum corneum (SC) was 10.61%. The in vivo studies showed that the developed formulations decreased the edema and erythema in mice skin in more that 90%, assuring, at least, the same anti-inflammatory effect compared with the commercial cream. PT placebo demonstrated to contribute to restore the skin barrier by increasing the amount of lipids within the human skin.

Safety assessment and biological effects of a new cold processed SilEmulsion for dermatological purpose

It is of crucial importance to evaluate the safety profile of the ingredients used in dermatological emulsions. A suitable equilibrium between safety and efficacy is a pivotal concern before the marketing of a dermatological product. The aim was to assess the safety and biological effects of a new cold processed silicone-based emulsion (SilEmulsion). The hazard, exposure, and dose-response assessment were used to characterize the risk for each ingredient. EpiSkin assay and human repeat insult patch tests were performed to compare the theoretical safety assessment to in vitro and in vivo data. The efficacy of the SilEmulsion was studied using biophysical measurements in human volunteers during 21 days. According to the safety assessment of the ingredients, 1,5-pentanediol was an ingredient of special concern since its margin of safety was below the threshold of 100 (36.53). EpiSkin assay showed that the tissue viability after the application of the SilEmulsion was 92 ± 6% and, thus considered nonirritant to the skin. The human studies confirmed that the SilEmulsion was not a skin irritant and did not induce any sensitization on the volunteers, being safe for human use. Moreover, biological effects demonstrated that the SilEmulsion increased both the skin hydration and skin surface lipids.