Influence of nanocrystal size on the in vivo absorption kinetics of caffeine after topical application

Topical caffeine-loaded nanostructured lipid carriers for enhanced treatment of cellulite: A 32 full factorial design optimization and in vivo evaluation in rats

The goal of this study was the development and evaluation of semisolid caffeine (CAF) loaded nanostructured lipid carriers (NLCs) for topical treatment of cellulite. CAF-loaded NLC formulations were prepared via high-speed homogenization followed by ultrasonication. A 32 full factorial design was employed for formulation optimization. The total lipid content (%) and the liquid lipid content per total lipids (%) were chosen as factors, whereas particle size (PS), polydispersity index (PDI), zeta potential (|ZP|) and viscosity (VIS) were selected as responses. The design suggested CAF-NLC3 as the optimum formulation consisting of a total lipid content of 15% w/w (palmitic acid and soft paraffin/isopropyl myristate, 7:3 w/w) and a surfactant content of 10% w/w (Tween 80/lecithin, 8:1.2 w/w). CAF-NLC3 revealed PS, PDI, ZP, VIS and CAF content values of 318.8 nm, 0.253, -41.1 mV, 18.0 Pa.s and 97.57%, respectively. It showed a pseudoplastic rheological behavior, acceptable pH value (5.25), good spreadability (1.12 mm2/g) and spherical shape employing transmission electron microscopy. Differential scanning calorimetry and X-ray diffraction demonstrated the amorphization of CAF in CAF-NLC3. CAF-NLC3 remained stable for 3 months at room and refrigeration conditions. A single topical application of CAF-NLC3 on shaved abdominal skins of Wistar rats revealed enhanced skin retention of CAF by 2-fold and 1.4-fold after 4 h when compared with plain CAF gel (CAF-P) and marketed CAF gel (CAF-M), respectively. Furthermore, CAF-NLC3 exhibited a superior anti-cellulite activity in comparison with CAF-P and CAF-M through elevating extracellular matrix components (collagen 1, elastin and hyaluronic acid) and stimulating the brown adipose tissue thermogenesis via up-regulating UCP1 and PPAR-γ expression. In addition, CAF-NLC3 prominently increased lipolysis through HSL activity and decreased pro-inflammatory cytokines such as ICAM-1 and VCAM-1 after 30 days of treatment on a high fat diet-induced cellulite rat model. These findings were further confirmed by histopathological examination supported by morphometric analysis. Therefore, incorporation of CAF in a semisolid NLC formulation would be a promising cosmetic approach for the topical treatment of cellulite.

Overview of Caffeine Effects on Human Health and Emerging Delivery Strategies

Caffeine is a naturally occurring alkaloid found in various plants. It acts as a stimulant, antioxidant, anti-inflammatory, and even an aid in pain management, and is found in several over-the-counter medications. This naturally derived bioactive compound is the best-known ingredient in coffee and other beverages, such as tea, soft drinks, and energy drinks, and is widely consumed worldwide. Therefore, it is extremely important to research the effects of this substance on the human body. With this in mind, caffeine and its derivatives have been extensively studied to evaluate its ability to prevent diseases and exert anti-aging and neuroprotective effects. This review is intended to provide an overview of caffeine's effects on cancer and cardiovascular, immunological, inflammatory, and neurological diseases, among others. The heavily researched area of caffeine in sports will also be discussed. Finally, recent advances in the development of novel nanocarrier-based formulations, to enhance the bioavailability of caffeine and its beneficial effects will be discussed.

Nanocrystals in cosmetics and cosmeceuticals by topical delivery

The main issues with local delivery of cosmetics are their high sensitivity and limited drug loading of active pharmaceutical ingredient. Nanocrystal technology offers consumers cutting-edge and effective products and exhibits enormous development potential in the beauty business as a new delivery method to address the issue of low solubility and low permeability of sensitive chemicals. In this review, we described the processes for making NCs, along with the impacts of loading and the uses of different carriers. Among them, nanocrystalline loaded gel and emulsion are widely used and may further improve the stability of the system. Then, we introduced the beauty efficacy of drug NCs from five aspects: anti-inflammation and acne, anti-bacterial, lightening and freckle removal, anti-aging as well as UV protection. Following that, we presented the current scenario about stability and safety. Finally, the challenges and vacancy were discussed along with the potential uses of NCs in the cosmetics industry. This review serves as a resource for the advancement of nanocrystal technology in the cosmetics sector.

Skin permeation of curcumin nanocrystals: Effect of particle size, delivery vehicles, and permeation enhancer

Nanocrystals are characterized by high drug loading, low carrier toxicity, and great structural stability. Therefore, they are a promising and versatile strategy for enhancing the local delivery of insoluble drugs. They achieve this by improving skin adhesion, concentration gradients, and hair follicle accumulation, as well as generating corona diffusion (which forms through the overlap of dissolved drug molecules around a nanocrystal). The development of suitable formulations for enhancing the passive diffusion and/or follicular targeting of nanocrystals is of great importance to clinical practice. We sought to elucidate the influence of particle size, a penetration enhancer, and delivery vehicles on the follicular accumulation and passive dermal permeation of nanocrystals. For this purpose, curcumin nanocrystals (particle size: 60, 120, and 480 nm) were incorporated into xanthan gum gels (delivery vehicles) with propylene glycol (penetration enhancer). This evaluation was performed in a porcine skin model. The results showed that xanthan gum reduced the follicular penetration and passive skin accumulation of curcumin nanocrystals. The propylene glycol enhanced the skin penetration and retention of curcumin nanocrystals in vitro for 24 h. The curcumin nanocrystals of smaller particle size (i.e., 60 and 120 nm) displayed higher passive skin penetration versus those with larger particle size (i.e., 480 nm); however, the latter type showed deeper follicular accumulation. In conclusion, the delivery vehicles, penetration enhancer, and particle sizes examined in this study affect the dermal penetration and accumulation of curcumin nanocrystals. Hence, their effects should be adequately considered when designing formulations of such nanocrystals.

Nanoencapsulation of Tea Catechins for Enhancing Skin Absorption and Therapeutic Efficacy

Tea catechins are a group of flavonoids that show many bioactivities. Catechins have been extensively reported as a potential treatment for skin disorders, including skin cancers, acne, photoaging, cutaneous wounds, scars, alopecia, psoriasis, atopic dermatitis, and microbial infection. In particular, there has been an increasing interest in the discovery of cosmetic applications using catechins as the active ingredient because of their antioxidant and anti-aging activities. However, active molecules with limited lipophilicity have difficulty penetrating the skin barrier, resulting in low bioavailability. Nevertheless, topical application is a convenient method for delivering catechins into the skin. Nanomedicine offers an opportunity to improve the delivery efficiency of tea catechins and related compounds. The advantages of catechin-loaded nanocarriers for topical application include high catechin loading efficiency, sustained or prolonged release, increased catechin stability, improved bioavailability, and enhanced accumulation or targeting to the nidus. Further, various types of nanoparticles, including liposomes, niosomes, micelles, lipid-based nanoparticles, polymeric nanoparticles, liquid crystalline nanoparticles, and nanocrystals, have been employed for topical catechin delivery. These nanoparticles can improve catechin permeation via close skin contact, increased skin hydration, skin structure disorganization, and follicular uptake. In this review, we describe the catechin skin delivery approaches based on nanomedicine for treating skin disorders. We also provide an in-depth description of how nanoparticles effectively improve the skin absorption of tea catechins and related compounds, such as caffeine. Furthermore, we summarize the possible future applications and the limitations of nanocarriers for topical delivery at the end of this review article.

Effect of Vehicle Composition on the Preparation of Different Types of Dapsone Crystals for Topical Drug Delivery

Topical formulations composed of API-pure crystals have been increasingly studied, especially in regards to the impact of particle size in penetration efficiency. Less attention, however, has been devoted to the solid-state properties of drugs delivered to the skin. In this study, we address the effect of formulation composition on the crystal form existing in topical products. Dapsone (DAP) gel formulations were prepared by mixing an organic solution containing DAP with an aqueous solution containing polymers and preservatives. The organic solvent was chosen as ethoxydiglycol (DEGEE), polyethylene glycol (PEG), or 1-methyl-2-pirrolidone (MPR) to assess the impact of composition on DAP crystal form. Such solvent variations resulted in different particulate matter. In terms of crystalline nature, the presence of DEGEE in formulations induced the crystallization of DAP hydrate, while PEG cocrystal and a mixture of hydrate and MPR solvate crystallized from the same amounts of PEG and MPR, respectively. Microscopic analysis of the gels showed heterogeneous particles with different characteristics. The behavior of gels after application to the skin was also tested. Interestingly, the different formulations seemed to accumulate in different regions of the skin. This could be the result of the effect of vehicle composition/excipients on the characteristics of the skin, such as hydration. The site-specific accumulation, however, was more pronounced in crystal-loaded gels as opposed to blank formulations. These results indicate that future studies should consider the effect of formulation composition on the API crystal form landscape as part of the strategies used to successfully target drug delivery to the skin.

Particle Size Effect of Curcumin Nanocrystals on Transdermal and Transfollicular Penetration by Hyaluronic Acid-Dissolving Microneedle Delivery

Microneedles are one promising penetration enhancement vehicle to overcome the stratum corneum skin barrier, which hampers the penetration of drug nanocrystals by transdermal delivery. In order to clarify the particle size effect of nanocrystals on transdermal delivery, 60 nm, 120 nm, and 480 nm curcumin nanocrystals were fabricated and incorporated into dissolving hyaluronic acid polysaccharide microneedles. The microneedles showed good mechanical strength with 1.4 N/needle, possessing the ability to insert into the skin. The passive permeation results showed that the smaller particle size of 60 nm curcumin nanocrystals diffused faster and deeper than the larger 120 nm and 480 nm curcumin nanocrystals with size-dependent diffusion behaviors. Thereafter, higher concentration gradients and overlap diffusional coronas also formed in the skin layers by the smaller-particle-size nanocrystals. Furthermore, the diffusion rate of the smaller particle size of curcumin nanocrystals to the hair follicle was also higher than that of the larger curcumin nanocrystals. In conclusion, the particle sizes of curcumin nanocrystals influenced the transdermal and transfollicular penetration in deeper skin layers

A Nanocrystals-Based Topical Drug Delivery System with Improved Dermal Penetration and Enhanced Treatment of Skin Diseases

Topical drug delivery methods are important in the treatment of skin diseases. Drug nanocrystals, which are nanometersized particles of active pharmaceutical ingredients, offer efficient topical delivery with high stability, high drug loading capacity, steady dissolution, and sustained drug release profiles. The use of nanocrystals for the topical delivery of skin disease therapies is currently being evaluated; this review focuses on how nanocrystals facilitate active pharmaceutical ingredient transport across skin barriers, exploring the underlying transportation mechanisms of the nanocrystals and active pharmaceutical ingredient molecules to the dermal and epidermal skin cells. In topical delivery, previous skin treatments, choice of excipients and vehicles, and penetration enhancement strategies critically influence the topical delivery of drug nanocrystals. Various research and applications of drug nanocrystals in skin disease therapy are highlighted in this review, and intellectual property protection for drug nanocrystal formulations, clinical trial data, and products with commercial potential are also discussed.

Microdialysis on Ex Vivo Porcine Ear Skin Can Validly Study Dermal Penetration including the Fraction of Transfollicular Penetration-Demonstrated on Caffeine Nanocrystals

Common ex vivo methods for penetration investigations often fail to monitor transfollicular penetration appropriately. In the present investigation, the validity of dermal microdialysis on the ex vivo porcine ear skin to investigate penetration kinetics, including transfollicular penetration, was studied. In setup A, a caffeine nanocrystal formulation was compared to a non-particular caffeine gel formulation. In setup B, two caffeine nanocrystal formulations of different sizes (200 nm, 700 nm) were compared to each other. Microdialysis samples were collected for 46 h. After sampling, the skin layers were separated, homogenized, and caffeine was quantified in all samples. In setup A the area under the curve (AUC) after crystal gel formulation application was 12 times higher than after non-particular formulation application. Setup B showed an increased AUC of 42% in the microdialysis data when the 700 nm caffeine crystals were applied compared to the 200 nm crystals. The microdialysis data was supported by the separation, homogenization and extraction data. Microdialysis performed on ex vivo porcine ear skin is a novel experimental setup. It is of high interest for further investigations since it is able to also capture the impact of follicular and transfollicular penetration kinetics as no other ex vivo setup can.