A Facile Bifunctional Strategy for Fabrication of Bioactive or Bioinert Functionalized Organic Surfaces via Amides-Initiated Photochemical Reactions

The excellent potential of organic polymeric materials in the biomedical field could be exploited if their interfacial problem could be fully resolved. A necessary prerequisite to this purpose often involves the simple but effective synthesis of a bioactive surface to endow polymer surfaces with high reactivity toward efficient biomolecules conjugation and a bioinert surface to prevent nonspecific adsorption of nontarget biomolecules. Although the corresponding research has been an important topic, actually few strategies could pave the way to comprehensively and simply tackle both of the bioactive and bioinert surfaces preparation issues. Herein we report an extremely simple and integrative bifunctional method that could efficiently tailor an organic material surface toward both bioactive and bioinert functions. This method is based on the use of an amides-initiated photochemical reaction in a confined space, which depending on the type of solutes used, results in the incorporation of primary amine groups or surface carbon radicals on an inert polymer surface. The grafted amine group could be used as a highly reactive site for biomolecule conjugation, and the surface carbon radical could be used to initiate radical graft polymerization of antifouling polymer brushes. We expect this simple but powerful method could provide a general resolution to solve the interfacial problem of organic substrate, offering a low-cost practical approach for real biomedical applications

Self-Assembled Monolayer-Assisted Negative Lithography

Self-assembled monolayers (SAMs) have been widely employed as etching resists in wet lithography systems to form patterns in which the ordered molecular packing of the SAM regions significantly delays the etchant attack. A generally accepted recognition is that the SAMs ability to resist etching is positively correlated to the quality of the surface-assembled structures, and a more ordered molecular packing would correspond to a better etching resistance. Such a classical belief is debated in the present work by providing an alternative SAM-assisted negative lithography where ordered SAM regions are etched more quickly than their disordered counterparts. This method features a unique photoirradiation-imprinted patterning process that simply consists of two steps: (1) UV irradiation on an OH-terminated SAM-modified gold surface through a photomask and (2) the subsequent immersion of the exposed substrate in an aqueous etching solution of <i>N</i>-bromosuccinimide/pyridine to develop a wet lithographic pattern. The entire experimental process reveals a finding from previous work that the etching rate on the UV-exposed regions with disordered molecular packing could be modulated to be slower than that in the unexposed well-defined SAM regions. Longer irradiation times would also revert the patterns from negative to positive. Thus, by merely using one kind of SAM-modified surface to provide both positive and negative micropatterns on gold layers, one could obtain flexible opportunities for high-resolution micro/nanofabrication resembling photolithography

Sequences and net charges of hBD-3, and N-terminus deletion analogs.

<p>Sequences and net charges of hBD-3, and N-terminus deletion analogs.</p

Antibacterial activity at increasing NaCl concentrations of hBD-3 and hBD-3Δ4 against fifteen <i>E. coli</i> clinical isolates.

<p>Antibacterial activity at increasing NaCl concentrations of hBD-3 and hBD-3Δ4 against fifteen <i>E. coli</i> clinical isolates.</p

Antibacterial activity at increasing NaCl concentrations of hBD-3 (A), hBD-3Δ4 (B), hBD-3Δ7 (C) and hBD-3Δ10 (D) against nine bacterial strains or species; and of hBD-3 and analogs against E. coli ATCC 25922 (E) and <i>E. faecium</i> ATCC 6057 (F).

<p>Error bars show the SDs of experiments performed in triplicate. Non parametric tests were used in the statistical analysis. ** Significantly different (<i>P</i> < 0.01) from the activity of wild-type hBD-3. ^## Significantly different (<i>P</i> < 0.01) from the activity of hBD-3 at 0 mM NaCl.</p

Steady-State Kinetic Constants for NDM-1 and Various Substrates

<p>Steady-State Kinetic Constants for NDM-1 and Various Substrates</p

Zinc dependence of the NDM-1-catalyzed hydrolysis of various substrates.

<p>Measurements were made with 0.5 mM substrates and increasing ZnSO₄ concentrations in the assay solution. Penems: penicillin G and piperacillin. Cephems: cefepime and ceftazidime. Carbapenem: biapenem.</p

Coomassie blue stained 12% SDS-PAGE of purified NDM-1.

<p>The highly purified and soluble NDM-1 is shown. The molecular weight of NDM-1 is approximately 28 kDa.</p

Effects of the pH, temperature, and EDTA on NDM-1.

<p>A: pH dependence of NDM-1 at 25°C. The enzyme was incubated in buffers with various pH values for 20 min at 30°C before assaying with 0.5 mM meropenem as a substrate. Averages are reported based on three independent measurements. B: Temperature dependence of NDM-1 at pH 7.5. The enzyme was incubated at different temperatures (5°C to 70°C) for 20 min before assaying with 0.5 mM meropenem as a substrate. Averages are reported based on three independent measurements. C: Determination of the IC₅₀ of EDTA against NDM-1. The enzyme (0.5 mg/ml NDM-1) was incubated in buffers with various EDTA concentrations [final = 10 mM HEPES (pH 7.5)] for 10 min at 30°C before assaying with 0.5 mM meropenem as a substrate. The IC₅₀ value is approximately 412 nM.</p