(357c) Hydrophilic and Hydrophobic Functional Group Interactions on Organic Crystals Coated with SiO2 Nanolayers By Physical Vapor Deposition

The purpose of this research work is to study the surface interactions of functional hydrophilic and hydrophobic forces with nanolayers of pharmaceutical additives coated on active pharmaceutical ingredient (API) [acetaminophen (APAP)] and excipient [lactose (Lc)] crystal surfaces. APAP and Lc crystals were developed in the lab and Atomic Force Microscopy (AFM) was used to investigate the effect of chemical nature of both excipient and API on adhesion forces. Physical Vapor Deposition (PVD) was used to coat the crystals with 10 nm, 20 nm and 50 nm thin layers of SiO₂. Uncoated and coated crystals were compared with respect to their adhesion forces. AFM probes were functionalized with hydrophilic and hydrophobic groups of 7-carboxy 1-heptane thiol and 1-decane thiol. It was found that the adhesion forces increased on both Lc and APAP crystal planes. Functionalized hydrophilic forces was found to be higher than the hydrophobic force on SiO₂ coated surfaces. Adhesion of functionalized groups was phenomenally affected by the chemical nature of crystals.