Efficient and versatile supramolecular functionalization of polysilicon microchips with cationic amphiphile salts for incorporation of therapeutics

A major challenge in working with suspended microchips for biosensing and drug-delivery lies in selecting an approach that produces highly ordered self-assembled monolayers during functionalization, along with identifying straightforward techniques for their characterization and quantification. In the current work, we aim to overcome these challenges by employing different supramolecular functionalization methods to identify and optimize robust approaches for achieving homogeneous functionalization, particularly with microchips in suspension. For this purpose, polysilicon microchips (PSµCs), fabricated by photolithographic techniques, were functionalized with gemini pyridinium and imidazolium derivatives through either covalent or non-covalent approaches followed by supramolecular functionalization of a porphyrin, which was used as a fluorophore to enable characterization. To explore the versatility of the methodology, we alternatively functionalized PSµCs with gemini bipyridinium salts as encapsulating agents which incorporated π-excessive neurotransmitters in a supramolecular manner. Contact angle measurements and MALDI-ToF mass spectrometry confirmed the extent of surface functionalization. Fluorescence microscopy also verified the incorporation of porphyrin and neurotransmitters with high homogeneity on the released microchips in suspension. UV-vis absorption spectroscopy exhibited negligible release of the porphyrin, along with a high loading capacity. In vitro assays also showed high cell viability in the presence of functionalized microchips. Overall, this functionalization approach overcomes modification challenges by effective and versatile incorporation of therapeutic agents on patterned wafers or suspended microchips for the development of biomedical devices.