Targeting tacrolimus to deeper layers of skin with improved safety for treatment of atopic dermatitis

Atopic dermatitis (AD) is chronically relapsing eczematous skin disorder having significant impact worldwide. Tacrolimus is the drug-of-choice which inhibits T-cell activation resulting in suppression of inflammation. However, despite being effective, most common adverse events of tacrolimus are low-and-variable bioavailability, burning sensation and pruritus at application site, which prompt for development of novel carrier that could effectively target tacrolimus to site-of-action without producing undesirable side-effects. Tacrolimus-loaded lipid-nanoparticles (T-LN) were prepared and optimized. DSC and FT-IR have been employed to study drug-excipient incompatibility and encapsulation of drug in lipid which was further confirmed by 1H NMR. In vitro studies revealed much higher drug release, skin penetration and enhanced skin accumulation as compared to reference Protopic®. In vitro and in vivo occlusion studies demonstrated similar occlusiveness for T-LN and reference however; T-LN showed significantly higher drug levels penetrating into deeper skin layers where dendritic cells responsible for immunopathogenesis of AD mainly reside. In-vivo skin retention demonstrated 3.36, 30.81 and 28.68-times higher stratum corneum, epidermal and dermal levels respectively compared to reference. Visualization of cutaneous uptake in-vivo using CLSM confirmed targeting to deeper skin layers and Draize test showed no skin irritation with PII 0.00. Thus T-LN displayed superior performance, effective skin targeting and improved safety as compared to reference

Development and evaluation of colloidal modified nanolipid carrier: Application to topical delivery of tacrolimus

Low solubility of tacrolimus in carrier matrix and subsequent poor in vivo bioavailability was overcome by constructing modified nanolipid carrier (MNLC) as a novel approach. The aim of this study was to develop MNLC with enhanced drug solubility in carrier lipid matrix using lipophilic solubilizers for topical delivery. Comprehensive characterization of tacrolimus-loaded MNLC (T-MNLC) was carried out for particle size, morphology, and rheology. Lipid modification resulted in the formation of less perfect crystals offering space to accommodate the dissolved drug leading to high entrapment efficiency of 96.66%. Compatibility and mixing behavior of carrier constituents was evaluated using DSC, FT-IR, and 1H NMR. T-MNLC displayed sufficient stability that could be attributed to possibility to reduce total lipid concentration in carrier. T-MNLC-enriched gels showed significantly higher in vitro drug release, skin permeation, and in vivo bioavailability with dermatopharmacokinetic approach in guinea pigs compared to commercial ointment, Protopic® as reference. Penetration-enhancing effect was confirmed using gamma scintigraphy in vivo in rats. Radioactivity remained localized in skin at the application site avoiding unnecessary biodisposition to other organs with prospective minimization of toxic effects. Skin irritation studies showed T-MNLC to be significantly less irritating than reference. Research work could be concluded as successful development of novel T-MNLC using lipophilic solubilizers to increase the encapsulation efficiency of colloidal lipid carriers with advantage of improved performance in terms of stability and skin localization

Development and evaluation of topical formulation containing solid lipid nanoparticles of vitamin A

The purpose of this research was to investigate novel particulate carrier system such as solid lipid nanoparticles (SLN) for topical application of vitamin A palmitate and to study its beneficial effects on skin. Topical gels enriched with SLN of vitamin A were prepared. The solid lipid nanoparticulate dispersion was prepared using high-pressure homogenization technique and was incorporated into polymeric gels of Carbopol, Pemulen, Lutrol, and Xanthan gum for convenient application. The nanoparticulate dispersion and its gels were evaluated for various parameters such as particle size, in vitro drug release, in vitro penetration, in vivo skin hydration, and skin irritation. The solid lipid nanoparticulate dispersion showed mean particle size of 350 nm. Differential scanning calorimetry studies revealed no drugexcipient incompatibility. In vitro release profile of vitamin A palmitate from nanoparticulate dispersion and its gel showed prolonged drug release up to 24 hours, which could be owing to embedment of drug in the solid lipid core. In vitro penetration studies showed almost 2 times higher drug concentration in the skin with lipid nanoparticle-enriched gel as compared with conventional gel, thus indicating better localization of the drug in the skin. In vivo skin hydration studies in albino rats revealed increase in the thickness of the stratum corneum with improved skin hydration. The developed formulation was nonirritant to the skin with no erythema or edema and had primary irritation index of 0.00. Thus it can be concluded that SLN represents a promising particulate carrier having controlled drug release, improved skin hydration, and potential to localize the drug in the skin with no skin irritation

Development and evaluation of colloidal modified nanolipid carrier: Application to topical delivery of tacrolimus, Part II – In vivo assessment, drug targeting, efficacy, and safety in treatment for atopic dermatitis

In atopic dermatitis (AD), topical anti-inflammatory therapy with skin barrier restoration to prevent repeated inflammatory episodes leads to long-term therapeutic success. Tacrolimus, although effective against AD, is a challenging molecule due to low solubility, low-penetration, poor-bioavailability, and toxicity. Part I of this paper, reported novel modified nanolipid carrier system for topical delivery of tacrolimus (T-MNLC), offering great opportunity to load low-solubility drug with improved entrapment efficiency, enhanced stability and improved skin deposition. Present investigation focused on restoration of skin barrier, site-specific delivery, therapeutic effectiveness, and safety of novel T-MNLC. T-MNLC greatly enhanced occlusive properties, skin hydration potential and reduced transepidermal water loss. This might help to reduce the number of flares and better control the disease. Cutaneous uptake and drug deposition in albino rats by HPLC and confocal laser scanning microscopy revealed prominently elevated drug levels in all skin strata with T-MNLC as compared to reference. T-MNLC demonstrated efficient suppression of inflammatory responses in BALB/c mice model of AD. Safety assessment by acute and repeated-dose dermal toxicity demonstrated mild keratosis and collagenous mass infiltration at the treatment area with repeated application of reference. Interestingly, T-MNLC showed no evident toxicity exhibiting safe drug delivery. Thus, novel T-MNLC would be a safe, effective, and esthetically appealing alternative to conventional vehicles for treatment for AD