Encoded nanopore for single molecule detection and Enantiomers discrimination

Presently, I am doing research on encoded nanopore which can be used as nano sensor for single molecule detection and can also be used to discriminate the enantiomers. Abstract is as follows:

Nanopore, pore with dimension of nm, serves as ultra sensitive novel devices for sensing the single molecule. The principle driving this nano sensor is that when a target molecule traverses or binds in the lumen nanopore, they characteristically block the ion pathway, resulting change in conductance of target specific. The characteristics change in conductance is unique for each type of molecules, therefore serving as a fingerprint for target identification and quantification. This nanopore technology can provide unique biosensing platforms for detecting nucleic acid (DNA)  and peptide molecules, high precision of molecular transportation like in drug delivery and the study of single molecule chemistry.

Protein pores that have receptors attached to them are target-selective, but their real-time applications are limited by the fixed pore size and fragility of the lipid membrane into which the protein pores are embedded. Also, synthetic nanopores are more stable and provide flexible pore sizes, but the selectivity is low when detecting in the translocation mode. Even though the nanopore has been functionalized with recognizing groups such as antibodies, these nanopores fail to bind individual target molecules. Distinguishing between binding and translocation blocks remains unsolved.

Aptamers, or “synthesized antibodies,” which are short DNA or RNA segments that are created by in vitro evolution and have high sensitivity and selectivity, are encoded in the nanopore which has several advantages like:more durable than most protein receptors, simpler to synthesize, modify, and immobilize using low cost methods. In contrast to antibodies, aptamers are much smaller than their targets, rendering target blockades in the nanopore much more distinguishable.

Selectivity can be checked by comparing   the response of AIgE/A-ricin-modified nanopore in different molecular species, where block like characteristics that are seen in original form can’t be obtained. This nanopore adopts the receptor attachment mode, rather than the molecular translocation mode, for single-molecule detection. Only molecules that are recognized by the immobilized receptor are able to yield featured block signals, providing high selectivity. The pore size does not need to match the target molecule dimension. Also it has increased the detection sensitivity to ~100 fM. We can also discriminate the enantiomers as R and S enantiomers have different current characteristics like one having more reduced current than others with narrower amount of time.

For future applications, these can be particularly useful in real-time applications- the digital signal of the discrete blocks distinguishes them from the analog background signal, hence possibility of real time sensor.

 

References:

1. Gu et al.,” Aptamer encoded nanopore for Ultrasensitive Detection of Bioterrorist Agent Ricin at Single Molecule Detection” , IEEE EMBS Journal, 2009,  6699-6702

2. Ding et al.,”Capturing single molecule of Immunoglobulin and Ricin with an Aptamer encoded Glass Nanopore”, Anal Chem, 2009, 81, 6649-6655

3. Gao et al. “A simple method of creating a nanopore-terminated probe for single-molecule enantiomer discrimination”, Anal Chem., 2009, 81, 80-86