Genefine L. Sapateh - Clark Atlanta University
Co-Author(s): Amrit Shirma and Ian Stubbs, Clark Atlanta University, GA
Electroactive nanofibers decorated with functional groups that specifically interact with biomarkers have tremendous potential to be utilized as single molecule detectors. Previous investigations in our group used functionalized and processable electronic conductive polythiophenes to study polymer-biomarker interactions. Another approach is to use a normally insulating polymer and mix it with single wall carbon nanotubes (SWCNT) to obtain a functional conductive composite. The advantages of using these composite nanostructures include good electrical sensitivity and biocompatibility because of their sizes relative to biomolecules. Fabrication of the electroactive composite into nanofibers has been shown to be effective not only as carriers of therapeutic agents but also as the active component in a biosensor. Nanofibers can be conveniently prepared by electrospinning. Variables effecting the quality of nanofibers include polymer molecular weight, polymer type and solution viscosity. The molecular weight, concentration, and microphase separation in the nanofibers contributes to the overall physical characteristics of the nanofibers. In this study we used a thermoplastic elastomeric triblock copolymer as an additive to prepare nanofibers with significantly improved physical properties.
The triblock copolymer poly(styrene)-b-poly(dimethylsiloxane)-b-poly(styrene) (PS-b-PDMS-b-PS)was synthesized by living anionic polymerization. Each block was 10 K in molecular weight. A solution of PS-b-PDMS-b-PS /PS, having a w/w ratio of 1:5 in DMF, along with SWCNT 1% wt were electrospun onto silicon wafer at 10kV. A flow rate of 20μl/min was used in the electrospinning. The fibers were characterized by SEM. I-V plots of the fibers were determined from readings detected using a four-point probe. A solution with PS 900,000 and SWCNT, w/w ratio of 100:1, was also spun for comparison with the fiber prepared using the triblock copolymers.
The SEM images of the triblock composite showed continuous uniform fibers and appears to be well defined at 10.0 μm. The diameters of the fibers was approximately 5 μm. IV plots showed a linear plot, with a calculated resistance of 109 Ω. The pure PS/SWCNT composite was difficult to spin into fibers because at high viscosity the polymer began to gel and did not produce continuous fibers. Therefore, the addition of the triblock copolymers significantly improved the processability and quality of the fibers. The synthesis of the triblock, the preparation of the fibers and the electronic properties of the fiber will be presented.
References: Olubi, O.; London, L.; Sannigrahi, B.; Nagappan,P.; Williams, M.; Khan, I.M. Fabrication of Bioactive Surfaces by Functionalization of Electroactive and Surface-Active Block Copolymers. Bioengineering. 2014, 1, 134-153.
Ahmet Koyun, Esma Ahlatcıoğlu and Yeliz Koca İpek (2012). Biosensors and Their Principles, A Roadmap of Biomedical Engineers and Milestones, Prof. Sadik Kara (Ed.), ISBN: 978-953-51-0609-8, InTech, Available from: http://www.intechopen.com/books/a-roadmap-of-biomedical-engineers-and-milestones/biosensor-andtheir-principles.
Funder Acknowledgement(s): Funding was provided by grants from NSF/CREST, AFRL, and ARO.
Faculty Advisor: Ishrat Khan, email@example.com