From fundamental to applied science, living things have long been a major source of inspiration for scientists. Nanopores are widely distributed in the natural world and are essential for a variety of biological functions, including the passage of biomolecules in and out of cells, and the transduction and processing of ionic currents. Motivated by the fundamental role of biological ion channels, the creation of fully abiotic solid-state nanochannels (SSNs) has been at the forefront of materials science in recent years. As a result, researchers are interested in tailorable nanochannels that resemble biological ion channels and have dimensions similar to those of biological molecules. My research project aims to explore the application of nanopores formed in silicon dioxide membranes using the ion track etching method. Specifically, the research evolves around charge-based molecular separation and biosensing. Our group has developed conical nanopore systems fabricated using the track etching method which offers narrow pore size distribution with tunable cone angle and precise control over the pore shape. As the applications of these nanopore membranes mainly depend on the pore tip radius and the surface characteristics of the pore inner walls, finetuning the surface properties at the nano scale plays a crucial role.  

Charge based separation of molecules using nanopore membranes is a promising technique for the purification of biomolecules such as viruses, proteins, and peptides from a complex biological mixture. Membrane-based separation processes are cost-effective, and easier to scale up. However, thin membranes with a narrow pore size distribution and well-defined surface properties are required for efficient separation but difficult to fabricate. In this study, we use the conically shaped nanopores to study the separation of charged dye molecules. The system showed excellent selectivity depending on the surface charge of the nanopore walls.

Typical silicon dioxide nanopores have a negative surface charge at neutral pH due to the hydroxyl groups (-OH) on the wall and we have successfully demonstrated that the membrane positively charged dyes permeate the membrane 50 times faster than the negatively charge ones. However, when the membrane is positively charged by attaching amine moieties on the surface, the membrane shows 15 times faster permeation of the negatively charged dyes compared to the positively charged ones. We have also shown that this membrane efficiently separates one dye from a mixture of dye solutions depending on the charge of the nanopores (shown in Figure 1).  

Another application of this nanopore system is biosensing. My research project focuses on the fabrication of a nanopore-based biosensors for detecting fatty acid binding protein 3 (FABP3). This protein is important for early detection of cardiovascular diseases. Cardiovascular diseases are a leading cause of death, and while several biomarkers are released during heart contractions, FABP3 appears in the blood within a very short time of 3 hours. The sensor can be fabricated in the silicon dioxide nanopore membrane by attaching antibodies that changes the ion current when the protein selectively attaches to them. The goal is to create a sensor that can detect FABP3 for timely diagnosis and treatment.

^{Figure 1 Charge-based molecular separation using conically shaped ion track-etched nanopores in silicon dioxide membranes}