Patterned substrates have been widely used in various applications, including arrays of biomolecules and cells, highthroughput assays, and direct target sensing.[1] In practice, those demands have been achieved by either of or a combination of two strategies: 1) direct incorporation of biomolecules or functional-group-containing molecules into desired patterns and 2) generation of functional-group-presenting patterns by way of chemical conversions on the surface. The former encompasses microcontact printing (mCP), [2] dip-pen nanolithography (DPN), [3] polymer-pen lithography (PPL), [4] microfluidic networks (mFNs), [5] and microarrays.[6] The latter utilizes the "turning-on" strategy, in which inactive substrates are switched to an active state to reveal organic functional groups, in most cases by electrochemical or photochemical conversions. [7] Patterned functional groups in both strategies are further used as chemical handles for immobilization of biomolecules, such as cell-adhesion ligands, enzyme substrates, proteins, oligosaccharides, and oligonucleotides, to afford patterned substrates. As a typical recent example, Rozkiewicz et al. reported on modified mCP for the preparation of oligonucleotide micropatterns.[8] In their report, oxidized PDMS stamps were first coated with positively charged dendrimers followed by negatively charged oligonucleotides in a layer-by-layer arrangement, and were transferred to a solid support for the generation of microarrays. Smith and co-workers introduced a photo-labile protecting group to a thiol functionality.[9] Various patterns of small molecules and proteins were prepared by using a photolithographic method in combination with thiol-specific conjugation chemistry. Yousaf et al. showed that ligand density and composition influence the rate of stem-cell differentiation by using hydroquinone-based electroactive substrates, which were patterned with a variety of ligands by using microarray technology.[10] Although these two strategies are reliable, well established, and, therefore, widely used, each of the strategies offers limitations on practical use as a general platform for ligand-patterned substrates. For instance, direct contact printing methods, such as mCP, cannot control ligand density on the surface, which can provide important quantitative information for use in experimental design. A concern with regard to the turning-on strategy is that in some cases activated functional groups require specified conjugation chemistry and, therefore, necessitate preparatory steps (tagging steps) to make the ligands compatible with the conjugation reaction.Herein, we describe a simple, efficient, and straightforward method for ligand patterning on a surface, induced by a non-invasive organic chemical reaction-which we have termed a chemical-reaction-induced patterning (CRIP)-and equipped with the capability for control of ligand density. In addition, our method is compatible with common patterning tools and conjugation chemistry. Herein, we demonstrate our strategy by using...

This paper describes a new, simple, and sensitive method for detecting two fluoroquinolones: enrofloxacin and its metabolite ciprofloxacin, which are widely used as drugs for humans and animals. We utilized gold nanoparticles (AuNPs) and laser desorption/ionization time-of-flight (LDI-TOF) mass spectrometry (MS) with a matrix-free format. An antibody for the drug was immobilized on a chip based on self-assembled monolayers (SAMs) on gold, and AuNPs were decorated with the drug along with a large excess of small molecules, called amplification tags (Am-tags). In this strategy, target drugs in solution bound to the antibody on the chip compete with the AuNP-immobilized drugs. The presence of targets was verified by the amplified LDI-TOF MS signals of Am-tags on AuNPs.

No abstract