Modelling insertion behaviour of PVP (Polyvinylpyrrolidone) and PVA (Polyvinyl Alcohol) microneedles

A comprehensive investigation into the effects of nonlinear material behaviour of polymeric (MN) and skin on the dynamics of the MN insertion in skin was undertaken in this study using experiments and numerical simulations. The nonlinearity of the material behaviour was incorporated by employing the Ramberg–Osgood and neo-Hooke an equations for stress–strain relationships for the MN materials and skin, respectively. For this purpose, a characteristic type of dissolving MN array was selected.

Highlights

• Nonlinear models for MNs and skin using Ramberg–Osgood and neo-Hookean equations.
• Strong alignment between experimental data and simulations for MN insertion.
• Simulations predict MN performance and stability, optimising designs pre-prototype.

This type of MN is made by a combination of poly(vinyl alcohol) and poly(vinyl pyrrolidone). The numerical simulations were validated using experimental investigations where the MNs were fabricated using laser-engineered silicone micromould templates technology. Young’s modulus, Poisson’s ratio, and compression breaking force for the MN polymers were determined using a texture analyser. The alignment between experimental findings and simulation data underscores the accuracy of the parameters determined through mechanical testing and mathematical calculations for both MN materials (PVP/PVA) and skin behaviour during the MN insertion.

This study has demonstrated a strong alignment between the experimental findings and computational simulations, confirming the accuracy of the established parameters for MNs and skin interactions for modelling MN insertion behaviour in skin, providing a solid foundation for future research in this area.

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Microneedle manufacturing

To prepare MN arrays, a mixture of 20% w/w polyvinylpyrrolidone (PVP) (MW 58 kDa, Ashland Kidderminster, UK) and 20% w/w polyvinyl alcohol (PVA) (MW 10kDa, Sigma-Aldrich, Dorset, UK) in deionised water was moulded using laser-engineered silicone micromould templates, following established methods (Tekko et al., 2020, Larrañeta et al., 2014b). In brief, the formulations were placed inside the moulds and centrifuged at 3500 RPM for 10 min to fill the moulds. Subsequently, samples were allowed to dry inside the moulds for at least 28 h. After drying, the MN arrays were removed, and the sidewalls were trimmed with scissors. The MN arrays were further dried at 37 °C overnight. The moulds used for this study contained an array of 11 × 11 conical needles (Fig. 1) with a base width and interspacing of 300μm and a needle height of 600μm (Fig. 2).

M. Soorani, Q.K. Anjani, E. Larrañeta, R.F. Donnelly, D.B. Das, Modelling insertion behaviour of PVP (Polyvinylpyrrolidone) and PVA (Polyvinyl Alcohol) microneedles, International Journal of Pharmaceutics, Volume 664, 2024, 124620, ISSN 0378-5173, https://doi.org/10.1016/j.ijpharm.2024.124620.

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