Amphoteric Cross-Linked Cellulose Nanoparticles as a Platform for Immobilization of Proteins and Cells, Enabling Bioanalyte Sensing

Cellulosic nanomaterials have significantly promoted the development of sensing devices, drug delivery, and bioreactor processes. Their synthetic flexibility makes them a prominent choice for immobilizing biomolecules or cells. In this work, we developed a practical and user-friendly approach to accessing cellulose nanoparticles (CNPs). The synthetic route is convenient and does not require a separate purification protocol. These particles are extensively characterized with FTIR, PXRD, TGA, DLS, and SEM. Later, we functionalized them with two chemically orthogonal handles: hydroxylamine and aldehyde. While the prior engaged glycan on the bacterial surface, the latter could capture an antibiotic to promote an in vitro controlled drug release. Besides, their dense functionalization enables efficient inter-CNP reactions, resulting in an amphoteric covalent cross-linked CNP capable of immobilizing proteins and cells. Also, it enables orthogonal dual immobilization to offer proximity control. Its capabilities were validated by installing an aldehyde-equipped bacterium and an activable fluorophore to offer a platform for detecting H₂S, a secretory reductant. It conveniently extends to H₂S detection in chicken eggs. Overall, the probe-, enzyme-, and bacterial cell-equipped amphoteric cross-linked CNP offers the potential to support bioprocesses for producing enzymes, secondary metabolites, vitamins, and hormones.