Effect of Kinetic and Thermodynamic Transitions of Confined Water on Biomolecules

In the last years, encapsulation of functional biomolecules (such as enzymes, proteins and antibodies) in three-dimensional nanoporous silica matrices has received considerable attention for its potential applications in biocatalysis, biosensing, and biopreservation.¹ A handful of studies conducted with bacteria, plant, and mammalian cells have shown that these complex microorganisms can also function when they are encapsulated in silica matrices.² When encapsulated in rigid permeable mesopores, mobility and proliferation of the microorganisms are prevented, while nutrients and by-products diffuse freely through the porous matrix. However, it is not known what mechanism(s) enables the biomolecules to be stable, and the microorganisms to be active, while they are mechanically confined in a matrix in a “no-growth” state. It is known that the motions and properties of water change when confined in nanopores. Therefore, we envision that the altered properties of confined water play a role in increasing the stability of biomolecules. This study is focused on understanding the effects of confinement on the kinetic and thermodynamic transitions of water, and identifying its effects on the structure of confined biomolecules. We have utilized Fourier Transform Infrared Spectroscopy (FTIR) to identify the different states and phase transitions of nanopore confined water at cryogenic temperatures. We have extended our analysis to quantify the structural changes in nanopore confined isolated and endogenous proteins of intact organisms.