Characterisation of inkjet-printed nanocrystals: challenges and opportunities Mengyang Hu, Mine Orlu and Asma Buanz School of Pharmacy, University College London, United Kingdom Low water solubility of most investigational new chemical entities (NCEs) is a main limiting factor of bioavailability enhancement with BCS Class II and Class IV drugs. The saturation solubility and the surface area are the two most considered parameters to be improved for a better dissolution behaviour of drugs. Physical approaches for drug micronization and nanonization have become popular, which can decrease the size of the API particles and enlarge the surface area and thus resulting in a higher dissolution rate 1 . Inkjet printing (IJP) has been proposed as an innovative technique in the pharmaceutical industry in recent years 2 with research mainly focusing on printing drugs onto oral films 3 and on maintaining the drug in an amorphous form for better dissolution properties 4 . However, the former strategy limits the application to fast-release and low-dose medications while the latter is limited by stability issues. Printing crystalline APIs in the form of nanocrystals would provide the advantage of physical stability and reduce the crystal size while maintaining the benefit of dose personalization that is offered by IJP. Nonetheless, limited work has been done utilizing IJP for this approach with key challenges facing characterisation. This work aimed to investigate formulating and characterisation of nifedipine nanocrystals using IJP. Nifedipine is a poorly soluble drug and is classified as a BCS II drug. In this study, it was formulated as a stable aqueous nanosuspension with the application of precipitation-ultrasonication technique 5 and then printed onto non-porous and porous polymeric substrates using piezoelectric IJP. Factors that may affect the printed drug products were studied. Raman microscopy was applied to characterise the physical form of the printed drug while scanning and optical electron microscopy were used for studying their morphology. Nifedipine nanocrystals (average size = 450nm) were successfully printed (Fig.1). Raman microscopy showed some characteristic peaks for the crystalline form for the as-received drug were also observed in the printed sample while peak shifts were also observed (Fig.2). Further investigation is looking at understanding the reason causing the shift. Ongoing work is also examining utilizing Dynamic mechanical analysis (DMA) to study the effect of the printed drugs on the mechanical properties of the substrates and its impact on drug dissolution.
Fig.1 SEM image of printed nifedipine
Fig. 2 Raman spectra of the as-received nifedipine and printed nifedipine
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