Microwave-assisted synthesis and characterization of hydrophilically functionalized polygalacturonic acid.

Microwave-assisted synthesis of a new class of polymeric surfactants based on polygalacturonic acid (PGA) is presented. PGA is water-insoluble and not surface-active under normal conditions. Single-step hydrophilic modification of PGA with taurine (2-aminoethane sulfonic acid) renders it surface-active. The modification can be carried out either using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDCl) as a coupling agent or using microwave irradiation without a catalyst. Microwave irradiation significantly shortens reaction times and eliminates the need for a coupling agent. In all cases, functionalization was confirmed using 1H NMR, FTIR spectroscopy and elemental analysis. PGA-SO3 exhibits surface-active properties comparable to commercial surfactants, Triton X-100 and sodium lauryl sulfate. Detailed cytotoxicity evaluation performed using human dermal fibroblast (HDF) and human leukemic (HL-60) cell lines indicate that PGA-SO3 is not toxic even at 20 fold higher concentrations. These polymeric surfactants synthesized from PGA with no demonstrable cytotoxicity have the potential for serving as 'greener' alternatives to common petrochemical-based surfactants.

Biocatalytic Synthesis of Fluorescent Conjugated Indole Oligomers.

Fluorescent conjugated materials exhibiting reasonable biocompatibility that are capable of interacting with biological molecules are of interest for bio-sensing and imaging applications. Traditional approaches do not allow for the synthesis of conjugated materials in the presence of biologically relevant substrates. Further conjugated polymers synthesized using conventional methods are doped and not fluorescent. Here we explore the possibility of synthesizing fluorescent oligomers of indole using enzymes as catalyst under mild conditions. The peroxidase catalyzed coupling reaction presented here creates a photoluminescent material that allows for direct utilization (without purification and separation of the dopant) in biosensing applications. The polymerization reaction proceeds smoothly in just deionized water and ethanol. Monitoring of the absorption and fluorescence spectra over one hour shows that the concentration of both absorbing and emitting species grows steadily over time. The presence of anionic buffers and templates is shown to effectively retard the development of light emitting species and instead leads to the formation of an electrically doped conjugated polymer. Structural characterization through FTIR and ¹H-NMR analysis suggests that the oligomer is coupled through the 2 and 3 positions on the indole ring.

Micellar nanoreactors for hematin catalyzed synthesis of electrically conducting polypyrrole.

Enzymatic synthesis of doped polypyrrole (PPy) complexes using oxidoreductases (specifically peroxidases) is very well established "green" methods for producing conducting polypyrrole. The importance of this approach is realized by the numerous potential opportunities of using PPy in biological applications. However, due to very high costs and low acid stability of these enzymes, there is need for more robust alternate biomimetic catalysts. Hematin, a hydroxyferriprotoporphyrin, has a similar iron catalytic active center like the peroxidases and has previously shown to catalyze polymerization of phenol monomers at pH 12. The insolubility of hematin due to extensive self-aggregation at low pH conditions has prevented its use in the synthesis of conjugated polymers. In this study, we have demonstrated the use of a micellar environment with sodium dodecylbenzenesulfonate (DBSA) for biomimetic synthesis of PPy. The micellar environment helps solubilize hematin, generating nanometer size reactors for the polymerization of pyrrole. The resulting PPy is characterized using UV-visible, Fourier transform infrared, and X-ray photoelectron spectroscopy and reveals the formation of an ordered PPy/DBSA complex with conductivities approaching 0.1 S/cm.