Microgel-based inks for paper-supported biosensing applications.

As a first step for the development of biosensing inks for inexpensive paper-based biodetection, we prepared paper strips printed with carboxylic poly( N-isopropylacrylamide) microgels that were modified either with an antibody or with a DNA aptamer. We found that the antibody and the DNA aptamer retained their recognition capabilities when coupled to microgel. The printed microgel remains stationary during chromatographic elution while the microgel-supported molecular recognition elements are accessible to their intended targets present in the elution solution.

Enzymatic manipulations of DNA oligonucleotides on microgel: towards development of DNA-microgel bioassays.

We demonstrate that DNA oligonucleotides covalently coupled to colloidal microgel can be manipulated by T4 DNA ligase for DNA ligation and by Phi29 DNA polymerase for rolling circle amplification (RCA). We also show that the long single-stranded RCA product can generate intensive fluorescence upon hybridization with complementary fluorescent DNA probe. We believe DNA-microgel conjugates can be explored for the development of DNA based bioassays and biosensors.

Adsorption and covalent coupling of ATP-binding DNA aptamers onto cellulose.

With the long-term goal of developing paper surfaces that will detect pathogens, we have investigated physical adsorption and covalent coupling as strategies for treating cellulose surfaces with a DNA aptamer that binds ATP. Physical adsorption was reversible and the isotherms fitted the Langmuir equation with an adsorption maximum of 0.105 mg/m2 at high ionic strength (300 mM NaCl, 25 mM Tris-HCl) and only 0.