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Bio-functionalized gold nanoparticles (AuNPs), which bio-specifically interact with biotin-(strept)avidin, were investigated in this study. AuNPs were functionalized with a synthetically-provided biotin-linked thiol (BLT), which was synthesized by amidation of the active ester of biotin with 2-mercaptoethylamine. The BLT-attached AuNP was bio-specific for streptavidin, making it potentially useful for biosensor applications. To test the bio-specific interactions, the colors, absorption spectra and TEM images were investigated for proteins such as streptavidin, cytochrome C, myoglobin and hemoglobin. The colors and absorption spectra changed when streptavidin was added to the BLT-attached AuNP solution. However, the color and spectra did not change when the other proteins were added to the same solution. These results show that the AuNPs provided a colloidal solution with excellent stability and highly selective absorption characteristics for streptavidin as a target molecule. Proteins were also screened in order to identify a general strategy for the use of optical biosensing proteins based on AuNPs. In addition, TEM images confirmed that streptavidin led the BLT-attached AuNPs to aggregate or precipitate.

In this study, we have developed a new detection method using Si field effect transistor (FET)-type biosensors, which enables the direct monitoring of antigen-antibody binding within very high-ionic-strength solutions such as 1×PBS and human serum. In the new method, as no additional dilution or desalting processes are required, the FET-type biosensors can be more suitable for ultrasensitive and real-time analysis of raw sample solutions. The new detection scheme is based on the observation that the strength of antigen-antibody-specific binding is significantly influenced by the ionic strength of the reaction solutions. For a prostate specific antigen (PSA), in some conditions, the binding reaction between PSA and anti-PSA in a low-ionic strength reaction solution such as 10 µM phosphate buffer is weak (reversible), while that in high-ionic strength reaction solutions such as 1×PBS or human serum is strong.

Novel anthracycline analogues 2-9 as potential anticancer agents were synthesized from daunomycin (1a) and doxorubicin (1b). Compounds 2, 6, and 7 were prepared by the nucleophilic displacement type esterification of a 14-bromodaunomycin (1c) with a sodium lactate, and stearic acid, respectively. Compounds 3-5 and 7-9 were prepared by the reaction of either daunomycin (1a) or doxorubicin (1b) with L-lactic and stearic acids in the presence of EDCI/PP reagents.

On the way to study electro organic synthesis (EOS) utilizing alternating Mg electrodes, a novel synthetic route from the nitrobenzenes to symmetric azobenzenes was discovered in our laboratory. The brief review about EOS was introduced by us. The EOS is expected to be an important organic synthetic tool in future because of its diverse application in industry in addition to compatibility with green chemistry. In the previous paper, we reported the optimized reaction conditions for the electro reductive coupling of aromatic halides: Mg rod for both of anode and cathode under a constant current, LiClO4 as a electrolyte, THF or glyme 7 as a solvent. We have tried to extend EOS to other functional groups. Since nitrobenzenes were readily reduced under the various mild reaction conditions, we exposed several nitrobenzenes under EOS reaction conditions. Our reaction conditions were Mg for anode and cathode, LiClO4, THF, room temperature under a constant current (current density = 42 mA/cm). The currents of anode and cathode were alternated at an interval of 30 seconds in order to minimize the consumption of the metal. The reaction mixture was carefully monitored by TLC and then worked up when nitrobenzene 1 was completely disappeared. The new spot was isolated and characterized fully by TLC and spectroscopic methods with an authentic sample. To our surprise, it was azobenzene 2 instead of aniline 3 based on the previously reported paper. The optimized yield of 2 was 87.6 % with no trace of the desired aniline 3. The amount of Mg consumed during the reaction was less then 5.0% for every attempt (eq. 1).

Tego Science, Daerung Technotown 3. #101, 488 Ga san-dong, Gumcheon-gu, Seoul 153-803, KoreaReceived April 6, 2004Key Words : Stimuli-responsive surfaces, Bioadhesion, Surf ace-initiated polymerization, Thermoresponsive-ness, Poly(N-isopropylacrylamide)Stimuli-responsive surfaces, which switch their physical,chemical and biological properties in response to externalstimuli, have a great potential in many technologicallyimportant areas such as nanoelectromechanical systems,bioanalysis, and biomimetics.