Mathematical modelling of nanoparticle-mediated topical drug delivery to skin tissue

Mathematical modelling of microneedle-mediated transdermal delivery of drug nanocarriers into skin tissue and circulatory system

Microneedle-mediated transdermal delivery using nanocarriers can successfully overcome the barrier of the stratum corneum and protect drugs from elimination in skin tissues. However, the effectiveness of drug delivery to different layers of skin tissues and the circulatory system varies considerably, subject to the properties of the drug delivery system and delivery regime. How to maximise delivery outcomes remains unclear. In this study, mathematical modelling is employed to investigate this transdermal delivery under various conditions, using the skin model that is reconstructed based on the realistic skin anatomical structure. Treatment efficacy is evaluated in terms of drug exposure over time. The modelling results demonstrate the complex dependence of drug accumulation and distribution on the nanocarrier properties, microneedle properties and environment in different skin layers and blood. Specifically, delivery outcomes in the entire skin and blood can be improved by increasing the loading dose and reducing microneedle spacing. However, several parameters need to be optimised with respect to the specific location of the target site in the tissue for better treatment; these include the drug release rate, nanocarrier diffusivity in microneedle and skin tissue, nanocarrier transvascular permeability, nanocarrier partition coefficient between tissue and microneedle, microneedle length, wind speed and relative humidity. The delivery is less sensitive to the diffusivity and physical degradation rate of free drugs in microneedle, and their partition coefficient between tissue and microneedle. Results obtained from this study can be used to improve the design of the microneedle-nanocarrier combined drug delivery system and delivery regime.

Nonporous versus Mesoporous Bioinspired Polydopamine Nanoparticles for Skin Drug Delivery

The use of polydopamine-based bioinspired nanomaterials has shed new light on advanced drug delivery arising from their efficient surface functionalization. More recently, the polydopamine self-assemblies formed in two different modalities, i.e., nonporous and mesoporous nanoparticles, have begun to attract attention due to their expedient and versatile properties. However, their possibility for use in dermal drug delivery for local therapy, as well as their interaction with the skin, has not yet been demonstrated. Our study aimed to compare and explore the feasibility of the self-assembled nonporous polydopamine nanoparticles (PDA) and mesoporous polydopamine nanoparticles (mPDA) for local skin drug delivery. The formation of the PDA and mPDA structures was confirmed by the UV-vis-NIR absorption spectrum, the Fourier transform infrared spectroscopy, and the nitrogen adsorption/desorption isotherms. Using retinoic acid (RA) as the model drug, their effects on drug loading, release, photostability, skin penetration, and radical scavenging were investigated. Laser scanning confocal microscopy (LSCM) and hematoxylin and eosin (H&E) were introduced to probe their delivery routes and possible interaction with the skin. The results indicated that both PDA and mPDA could reduce the photodegradation of RA, and mPDA showed significantly better radical scavenging activity and drug loading capacity. The ex vivo permeation study revealed that both PDA and mPDA significantly enhanced the delivery of RA into the deep skin layers by comparison with the RA solution, in which follicular and intercellular pathways existed, and alteration in the structure of stratum corneum was observed. In light of drug loading capacity, size controllability, physical stability, as well as radical scavenging activity, mPDA was more preferable due to the improvement of these factors. This work demonstrated the feasibility and promising application of PDA and mPDA nanoparticles for dermal drug delivery, and the comparative concept of these two types of biomaterials can provide implications for their use in other fields.

Predictive Design and Analysis of Drug Transport by Multiscale Computational Models Under Uncertainty

Computational modeling of drug delivery is becoming an indispensable tool for advancing drug development pipeline, particularly in nanomedicine where a rational design strategy is ultimately sought. While numerous in silico models have been developed that can accurately describe nanoparticle interactions with the bioenvironment within prescribed length and time scales, predictive design of these drug carriers, dosages and treatment schemes will require advanced models that can simulate transport processes across multiple length and time scales from genomic to population levels. In order to address this problem, multiscale modeling efforts that integrate existing discrete and continuum modeling strategies have recently emerged. These multiscale approaches provide a promising direction for bottom-up in silico pipelines of drug design for delivery. However, there are remaining challenges in terms of model parametrization and validation in the presence of variability, introduced by multiple levels of heterogeneities in disease state. Parametrization based on physiologically relevant in vitro data from microphysiological systems as well as widespread adoption of uncertainty quantification and sensitivity analysis will help address these challenges.