(3eg) Functional Materials: Molecules, Polymers, Particles, and Fibers

My research is situated in between the biological and material sciences, where a variety of functional materials from small molecules to micron-sized polymeric fibers have been prepared. Such diverse materials have different functions depending on their sizes. Therefore, it is categorized into four different groups; molecules, polymers, particles, and fibers.

For small molecules, organic synthesis has been utilized to discover and develop new drugs including enzyme inhibitors (Thrombin¹ and HIV protease inhibitor²), antibiotics (Quinolone, Anti-Methicillin-Resistant Staphylococcus Aureus (MRSA), and Oral Cephalosporin), antivirus (Anti-Hepatitis B Virus (HBV)), and natural compounds. Such an extensive organic synthesis has offered a fruitful tool in my research, thus became a key platform for the other studies.

As a part of polymeric functional materials, organometallic polymers as novel nitric oxide (NO) generating biomaterials³ and new amperometric sensors⁴based on these materials have been developed. The NO generating polymers can catalyze the spontaneous decomposition of endogenous S-nitrosothiols found in blood (e.g., S-nitrosoalbumin, S-nitrosoglutathione, and S-nitrosocysteine) to produce NO locally at the polymer/blood interface for prolonged periods of time. Because NO has a variety of potent biological activities, including anti-platelet adhesion/activation, anti-proliferation of smooth muscle cell, anti-microbial, as well as wound healing, NOGPs have a variety of potential biomedical applications including stents, vascular grafts, indwelling sensors, catheters, and extracorporeal circuits in order to improve their biocompatibility.

The nano/micron sized anisotropic particles have been prepared by electrohydrodynamic (EHD) co-jetting. The prepared particles are comprised of two distinctive compartments within individual particles. Various combinations of different polymers, inorganic molecules (magnetite, titanium dioxide, gold nanoparticles, carbon nanotube, and silica), and dyes (optical and/or fluorescence) have been selectively embedded in each compartment,⁵ potentially useful for drug delivery, catalyst, and particle swimmer. Additionally, magnetic Janus particles have been studied for controllable self-assemblies that are highly ordered in two-dimensional arrangements including a hexagonal close packing, and applied into a form of magnetically switchable surface.⁶

A novel approach to manufacture multiblock magnetic nano/microwires is established via spatiotemporally programmable magnetic self assemblies and concomitant particle interconnections.⁷The other functional fibers fabricated by the EHD co-jetting are studied for de novo two-way shape memory polymers and anisotropic polymeric niches for stem cell differentiation.

References

1. Kim, S. S.; Hwang, S.; Kim, Y. K.; Yun, M. K.; Oh, Y. S., “Rational Design of Selective Thrombin Inhibitors” Bioorg. Med. Chem. Lett., 1997, 7, 769-774.
2. Lee, K. W.; Hwang, S.; Kim, C. R.; Nam, D. H.; Chang, J. H.; Choi, S. C.; Choi, B. S.; Choi, H.-w.; Lee, K. K.; So, B.; Cho, S. W.; Shin, H., “The Chemical Development of LB71350” Organic Process Research & Development 2003, 7, 839-845.
3. Hwang, S.; Cha, W.; Meyerhoff, M. E. “Polymethacrylates with Covalently Linked Copper(II)-Cyclen Complex for In Situ Generation of Nitric Oxide from Nitrosothiols in Blood” Angew. Chem. Int. Ed. 2006, 45, 2745-2748.
4. Hwag, S.; Cha, W.; Meyerhoff, M. E. “Amperometric Nitrosothiol Sensor Using Immobilized Organoditelluride Species as Selective Catalyst” Electroanalysis, 2008, 20, 270-279.
5. Hwang, S.; Roh, K.-H.; Lim, D. W.; Wang, G.; Uher, C.; Lahann, J. “Anisotropic Hybrid Particles Based on Electrohydrodynamic Co-Jetting of Nanoparticle Suspensions” Phys. Chem. Chem. Phys. 2010, 12, 11894-11899.
6. Hwang, S.; Nguyen, T. D.; Yoon, J.; Bhaskar, S.; Hitt, J.; Chickering, D.; Bernstein, H.; Glotzer, S. C.; Lahann, J. “Magentophoretic Surface Switching” 2012, In Submission.
7. Hwang, S.; Park, T.-H.; Lahann, J. “Spatiotemporally programmable Self-Assemblies of Magnetic Particles” 2012, In Submission.