Skin absorption studies of octyl-methoxycinnamate loaded poly(D,L-lactide) nanoparticles: Estimation of the UV filter distribution and release behaviour in skin layers

Nanoparticles as a Therapeutic Delivery System for Skin Cancer Prevention and Treatment

The use of nanoparticles (NPs) as a therapeutic delivery system has expanded markedly over the past decade, particularly regarding applications targeting the skin. The delivery of NP-based therapeutics to the skin requires special consideration owing to its role as both a physical and immunologic barrier, and specific technologies must not only take into consideration the target but also the pathway of delivery. The unique challenge this poses has been met with the development of a wide panel of NP-based technologies meant to precisely address these considerations. In this review article, we describe the application of NP-based technologies for drug delivery targeting the skin, summarize the types of NPs, and discuss the current landscape of NPs for skin cancer prevention and skin cancer treatment as well as future directions within these applications.

Synthesis and Characterization of Nanostructured Lipid Nanocarriers for Enhanced Sun Protection Factor of Octyl p-methoxycinnamate

Sunlight is important to health, but higher exposure to radiation causes early aging of the skin and skin damage that can lead to skin cancers. This study aimed at producing a stable octyl p-methoxycinnamate (OMC)-loaded nanostructured lipid carrier (NLC) sunscreen, which can help in the photoprotective effect. NLC was produced by emulsification-sonication method and these systems were composed of myristyl myristate (MM), caprylic capric triglyceride (CCT), Tween® 80 (TW), and soybean phosphatidylcholine (SP) and characterized by dynamic light scattering (DLS), zeta potential (ZP) measurement, atomic force microscopy (AFM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and in vitro release studies. Pre-formulation studies were performed changing TW concentrations and no differences were found at concentrations of 1.0 and 2.0%. Two selected formulations were designed and showed an average size of 91.5-131.7, polydispersity index > 0.2, and a negative value of ZP. AFM presented a sphere-like morphology and SEM showed ability to form a thin film. DSC exhibited that the incorporation of OMC promoted reduction of enthalpy due to formation of a more amorphous structure. Drug release shows up to 55.74% and 30.57%, and this difference could be related to the presence of SP in this formulation that promoted a more amorphous structure; the release mechanism study indicated Fickian diffusion and relaxation. Sun protection factor (SPF) evaluation was performed using NLC and presented values around 40, considerably higher than those observed in the literature. The developed formulations provide a beneficial alternative to conventional sunscreen formulations.

Using ordered mesoporous silica SBA-15 to limit cutaneous penetration and transdermal permeation of organic UV filters

Avobenzone (AVO), oxybenzone (OXY), and octyl methoxycinnamate (OMC), are widely used UV filters. The aim of this study was to investigate the effect of incorporation in mesoporous silica (SBA-15) on their cutaneous deposition and permeation. Stick formulations containing "free" and "incorporated" UV filters (SF1 and SF2, respectively) were prepared and characterized with respect to their physicochemical, thermal, and functional properties. Cutaneous delivery experiments using porcine skin with quantification by UHPLC-MS/MS, demonstrated that skin deposition of AVO and OXY after application of SF2 for 6 and 12 h was significantly lower than that from SF1 at each time-point (Student t-test, p < 0.05): e.g. OXY permeation across the skin was 30-, 12- and 1.5-fold lower after 6, 12 and 24 h, respectively, following application of SF2. Cutaneous biodistribution profiles of AVO and OXY to 800 µm evidenced a significant decrease in the amounts in the viable epidermis and dermis. In contrast, deposition of the more lipophilic OMC was not significantly different (p ˃ 0.05). In vitro photoprotective efficacy results demonstrated that adsorption/entrapment of UV filters enhanced the sun protection factor by 94%. In conclusion, SBA-15, an innovative mesoporous material, increased photoprotection by UV filters while reducing their cutaneous penetration and transdermal permeation.

Biodegradable bioadhesive nanoparticle incorporation of broad-spectrum organic sunscreen agents

Conventional emulsion-based sunscreen formulations are limited by postapplication epicutaneous penetration that increases the risk of allergic dermatitis, cellular damage, and filter photodegradation upon ultraviolet radiation (UVR) exposure. Encapsulation of the UVB filter padimate O within bioadhesive biodegradable nanoparticles (BNPs) composed of poly(d,l-lactic acid)-hyperbranched polyglycerol was previously shown to enhance UVR protection while preventing skin absorption. Herein, we assess the capacity of BNP co-incorporation of avobenzone and octocrylene to provide broad-spectrum UVR protection. The ratio of UV filters within nanoparticles (NPs) was optimized for filter-filter stabilization upon UV irradiation and maximum drug loading. In vitro water-resistance test showed significant particle retention at 85% over 3 hr. In a pilot clinical study, protection against UVR-induced erythema of BNPs was found to be comparable to the FDA standard P2. Thus, sunscreen formulations utilizing BNP incorporation of a combination of organic filters may offer key safety and performance advantages.

Encapsulation of cosmetic active ingredients for topical application--a review

Microencapsulation is finding increasing applications in cosmetics and personal care markets. This article provides an overall discussion on encapsulation of cosmetically active ingredients and encapsulation techniques for cosmetic and personal care products for topical applications. Some of the challenges are identified and critical aspects and future perspectives are addressed. Many cosmetics and personal care products contain biologically active substances that require encapsulation for increased stability of the active materials. The topical and transdermal delivery of active cosmetic ingredients requires effective, controlled and safe means of reaching the target site within the skin. Preservation of the active ingredients is also essential during formulation, storage and application of the final cosmetic product. Microencapsulation offers an ideal and unique carrier system for cosmetic active ingredients, as it has the potential to respond to all these requirements. The encapsulated agent can be released by several mechanisms, such as mechanical action, heat, diffusion, pH, biodegradation and dissolution. The selection of the encapsulation technique and shell material depends on the final application of the product, considering physical and chemical stability, concentration, required particle size, release mechanism and manufacturing costs.

Skin absorption and human exposure estimation of three widely discussed UV filters in sunscreens--In vitro study mimicking real-life consumer habits

Due to health concerns about safety, three UV-filters (Benzophenone-3, BP3, 10%; Ethylhexyl Methoxycinnamate, EHMC, 10%; Butyl Methoxydibenzoylmethane, BMDBM; 5%) were examined in vitro for absorption on full-thickness pig-ear skin, mimicking human in-use conditions. Kinetic profiles confirmed the rapid permeation of BP3; after the first hour of skin (frozen-stored) exposure to 2 mg/cm(2) (W/O sunscreen; recommended but unrealistic amount), about 0.5% of the applied dose passed into the receptor fluid. The absorption rate of filters was higher from W/O than from O/W emulsions. The fresh/frozen-stored skin permeability coefficient (0.83-0.54) for each UV filter was taken into account. Systemic Exposure Dosage of BP3, EHMC, BMDBM for humans as a consequence of (i) whole-body and (ii) face treatment with 0.5 mg/cm(2) of W/O sunscreen for 6-h skin exposure followed by washing and subsequent 18-h permeation (a realistic scenario) were estimated to be (i) 4744, 1032 and 1036 μg/kg-bw/day, and (ii) 153, 33 and 34 μg/kg-bw/day, respectively. From Margin of Safety for BP3, EHMC and BMDBM (i) 42, 485 and 192 as well as (ii) 1307; 15,151 and 5882, respectively, only the value of 42 (<100) for BP3 indicated a possible health risk. Escalation of a phobia towards all organic UV filters is undesirable.

Improved percutaneous delivery of ketoprofen using combined application of nanocarriers and silicon microneedles

Objectives

The aim of our study was to evaluate the effect of designing ketoprofen-loaded nanosized spheres and combining them with solid silicon microneedles for enhanced and sustained percutaneous drug delivery.

Methods

Ketoprofen-loaded nanoparticles (KET-NP) were designed by modified solvent displacement method, using poly (D, L-lactic acid) (PDLLA). All prepared nanoparticles were characterised with regard to their particle size distribution, morphology, surface properties, thermal behaviour, drug content, drug release and stability. In-vitro skin permeation studies were conducted on Franz-type diffusion cells using porcine skin treated with ImmuPatch silicon microneedles (Tyndall Nation Institute, Cork, Ireland).

Key findings

The study showed that uniform nanospheres were prepared with high encapsulation efficiency and retained stable for 2 months. After an initial burst release, the PDLLA nanoparticles were capable of sustaining and controlling ketoprofen release that followed Korsmeyer–Peppas kinetics. An enhanced flux of ketoprofen was observed in the skin treated with silicon microneedles over a prolonged period of time.

Conclusions

Following application of silicon microneedle arrays, KET-NP were able to enhance ketoprofen flux and supply the porcine skin with drug over a prolonged (24 h) period of time. Our findings indicate that the delivery strategy described here could be used for the further development of effective and painless administration systems for sustained percutaneous delivery of ketoprofen.

Vitamin K1-loaded lipid-core nanocapsules: physicochemical characterization and in vitro skin permeation

BACKGROUND

The incorporation of substances in nanocarriers can modulate and/or manage their delivery profiles (immediate or sustained) and permeation through skin. Consequently, drug nanencapsulation intended for topical treatment can reduce the systemic absorption of the substance.

OBJECTIVE

To obtain and characterize vitamin K1-loaded lipid core nanocapsules as well as to determine whether the nanoencapsulation influences the skin permeation of this vitamin.

METHODS

The skin permeation study was performed by means of Franz-type diffusion cells followed by the tape stripping and retention techniques. The vitamin K1-loaded lipid core nanocapsules were obtained by the preformed polymer precipitation method and the particles were characterized.

RESULTS

The nanocapsules presented average diameter of 211 ± 2 nm, pH of 5.7 ± 0.3, zeta potential of -14.9 ± 0.6 mV and drug content of 10.2 mg/mL (102.1%). The physical stability of the nanocapsule suspension was verified using multiple light backscattering analysis. The amount of vitamin K1 in the dermis after 8 h of drug permeation was higher when the nanocapsules were applied compared to the control. Moreover, retention in the outermost skin layer and a decrease in the skin permeation to the receptor compartment due to the nanoencapsulation were observed.

CONCLUSION

Thus, nanoencapsulation can lead to the selective permeation of vitamin K1 through the skin.

In vitro vs. in vivo tape stripping: validation of the porcine ear model and penetration assessment of novel sucrose stearate emulsions

Porcine ear skin is frequently used as a substitute for human skin in dermatological research and is especially useful for tape stripping experiments where the penetration of active substances into the uppermost skin layers is investigated. However, certain differences between the surface properties of these skin types exist, and reports on the comparability of tape stripping data obtained in vitro using porcine ear skin and data obtained in vivo on human forearm skin are scarce. Thus, we performed comparative tape stripping experiments in which the skin penetration of curcumin and fluorescein sodium from conventional microemulsions and hydrogels was investigated. In this context, the skin penetration potential of novel semi-solid macroemulsions and fluid nanoemulsions based on sucrose stearate was evaluated as well. The removed corneocytes were quantified by NIR-densitometry using recent correlation data for human and porcine proteins. The trends observed for the skin penetration into porcine ear skin were highly representative for the in vivo situation on human skin, confirming that the porcine ear is an excellent in vitro model for tape stripping experiments. Moreover, the validity of the NIR-densitometric approach for the quantification of both human and porcine stratum corneum proteins was confirmed in this study for the first time.