Molecular recognition force spectroscopy (MR-FS) was applied to investigate the dynamic interaction between aptamer GBI-10 and tenascin-C (TN-C) on human glioblastoma cell surface at single-molecule level. The unbinding force between aptamer GBI-10 and TN-C was 39 pN at the loading rate of 0.3 nN sec⁻¹. A series of kinetic parameters concerning interaction process such as the unbinding force f_u, the association rate constant k_on, dissociation rate constant at zero force k_off, and dissociation constant K_D for aptamer GBI-10/TN-C complexes were acquired. In addition, the interaction of aptamer GBI-10 with TN-C depended on the presence of Mg²⁺. This work demonstrates that MR-FS can be used as an attractive tool for exploring the interaction forces and dynamic process of aptamer and ligand at the single-molecule level. As a future perspective, MR-FS may be used as a potential diagnostic and therapeutic tool by combining with other techniques. Copyright © 2012 John Wiley & Sons, Ltd.

The fabrication of patterned microstructures in poly(dimethylsiloxane) (PDMS) is a prerequisite for soft lithography. Herein, curvilinear surface relief microstructures in PDMS are fabricated through a simple three-stage approach combining microcontact printing (μCP), selective surface wetting/dewetting and replica molding (REM). First, using an original PDMS stamp (first-generation stamp) with linear relief features, a chemical pattern on gold substrate is generated by μCP using hexadecanethiol (HDT) as an ink. Then, by a dip-coating process, an ordered polyethylene glycol (PEG) polymer-dot array forms on the HDT-patterned gold substrate. Finally, based on a REM process, the PEG-dot array on gold substrate is used to fabricate a second-generation PDMS stamp with microcavity array, and the second-generation PDMS stamp is used to generate third-generation PDMS stamp with microbump array. These fabricated new-generation stamps are utilized in μCP and in micromolding in capillaries (MIMIC), allowing the generation of surface micropatterns which cannot be obtained using the original PDMS stamp. The method will be useful in producing new-generation PDMS stamps, especially for those who want to use soft lithography in their studies but have no access to the microfabrication facilities.

Bacillus subtilis can form a spore, which is a dormant type of cell, when its external environment becomes unsuitable for vegetative growth. The spore is surrounded by a multilayered proteinaceous shell called a spore coat, which plays a crucial role in dormancy and germination. Of the over 70 proteins that form the spore coat, only a small subset of them affect its morphogenesis; they are referred to as morphogenetic proteins. How these morphogenetic proteins interact, and furthermore, how they build the ordered, functional coat layers is not well understood. Elucidating the self-assembly mechanism of individual proteins into such a complex structure may contribute to its potential use in nano-biotechnology applications for preparing highly organized, robust, and resistant proteinaceous layers. Herein, direct, noncovalent, low-affinity interactions between the spore-coat morphogenetic proteins SpoIVA, SpoVID, and SafA were studied by using single-molecule recognition force spectroscopy in vitro for the first time. Based on the real-time examination of interactions between these three proteins, a series of dynamic kinetic data were obtained. It was also observed that the SafA–SpoVID interaction was stronger than that of SafA–SpoIVA.