Hung-Yin Lin

Synthesis of Magnetic Molecularly Imprinted Poly(ethylene-co-vinyl alcohol) Nanoparticles and Their Uses in the Extraction and Sensing of Target Molecules in Urine

Superparamagnetic nanoparticles are of great current interest for biomedical applications in both diagnostics and treatment. Magnetic nanoparticles (MNP) can be manipulated by magnetic fields, so that when functionalized, they can be used for the purification and separation of biomolecules and even whole cells. Here we report combining the separation capabilities of MNPs with the functional (binding) capability of molecularly imprinted polymers. Albumin- creatinine-, lysozyme-, and urea-imprinted polymer nanoparticles were synthesized from poly(ethylene-co-ethylene alcohol) via phase inversion, with both target molecules and hydrophobic magnetic nanoparticles mixed within the polymer solution. Several ethylene:ethylene alcohol mole ratios were studied. The rebinding capacities for those three target molecules varied from 0.76 +/- 0.02 to 5.97 +/- 0.04 mg/g of molecularly imprinted magnetic nanoparticles. Lastly, the composite nanoparticles were used for separation and sensing of template molecules (e.g., human serum albumin) in real samples (urine) and results were compared with a commercial ARCHITECT ci 8200 system.

Ultrasound Mediates the Release of Curcumin from Microemulsions

Ultrasound is a powerful noninvasive modality for biomedical imaging, and holds much promise for noninvasive drug delivery enhancement and targeting. However, the optimal design of sound sensitive carriers is still poorly understood. In this study, curcumin, an important natural antioxidant and anticancer compound, was stably entrapped into microemulsion droplets with average size 20-35 nm. To release curcumin, low frequency (40 kHz) ultrasound at an intensity of 3.8 or 9.8 W/cm2 was applied to the microemulsions, using a probe sonicator. On insonation, much of the curcumin was released from the microemulsions and formed insoluble aggregates, as evidenced by decreased UV-vis absorption at 420 nm. The initial release rate (assayed by the rate of change of absorption) was as high as 0.11 microg/s (1.87%/sec) in phosphate buffered saline solution at neutral pH, but decreased at acidic pH. Interestingly, lower curcumin loading led to a more rapid release under insonation. Measurements of emulsion droplet size implicate droplet reorganization (fusion or fission) as an important contributing mechanism for the ultrasonic release of this compound. Although cargo in microemulsions is partitioned, rather than encapsulated (as in, for example, liposomes), these new results demonstrate that microemulsion carriers are feasible for some ultrasonic drug delivery applications.

Hydrolysis of magnetic amylase-imprinted poly(ethylene-co-vinyl alcohol) composite nanoparticles.

Molecularly imprinted polymers (MIPs) have frequently been employed as recognition elements in sensing applications, or for the controlled delivery of small molecule drugs. An equally important but less well studied application is the use of MIPs in the binding and immobilization of active enzymes. In this study, magnetic MIPs (MMIPs) recognizing the enzyme amylase were prepared using phase inversion of poly(ethylene-co-vinyl alcohol) (EVAL) solutions with 27-44 mol % ethylene in the presence of amylase. The size distribution, specific surface area, magnetization, and composition were characterized by dynamic light scattering (DLS), Brunauer-Emmett-Teller (BET) analysis, superconducting quantum interference devices (SQUID), and X-ray diffraction (XRD), respectively. The mean size of MMIPs was ~100 nm and the magnetization was 14.8 emu/g. The activities of both bound template and rebound enzyme was established by measuring glucose production via starch hydrolysis, at different temperatures, for MIPs with different compositions (wt % EVALs and mol % ethylene). The highest hydrolysis activity of MMIPs (obtained with 32 mol % ethylene) was found to be 1545.2 U/g. Finally, compared to the conventional catalysis process, MMIPs have the advantages of high surface area, suspension, easy removal from reaction, and rapid reload of enzyme. The good activity of amylase MMIPs persists after 50 cycles of starch hydrolysis.

Microcontact Imprinting of Algae on Poly(ethylene-co-vinyl alcohol) for Biofuel Cells

Hydrogen can be produced using microorganisms (e.g., bacteria and algae); algal production has the additional ecological benefit of carbon dioxide fixation. The conversion of hydrogen to electricity via fuel cells may be more efficient compared to other energy sources of electricity. However, the anode of biofuel cells requires the immobilization of microorganisms or enzymes. In this work, poly(ethylene-co-vinyl alcohol) (EVAL), was coated on the electrode, and green algae was microcontact imprinted onto the EVAL film. The readsorption of algae onto algae-imprinted EVAL thin films was compared to determine the ethylene content that gave highest imprinting effectiveness and algal binding. Scanning electron microscopy and fluorescence spectrometry were employed to characterize the surface morphology, recognition capacity, and reusability of the algae-imprinted cavities. The recognition of an individual algal cell by binding to the imprinted cavities was directly observed by video microscopy. Finally, the power and current density of the algal biofuel cell using the algae-imprinted EVAL-coated electrode were measured at about 2-fold higher than electrode sputtered platinum on poly(ethylene terephthalate).

Microcontact Imprinting of Algae for Biofuel Systems: The Effects of the Polymer Concentration

Microcontact imprinting of cells often involves the deposition of a polymer solution onto a monolayer cell stamp, followed by solvent evaporation. Thus, the concentration of the polymer may play an important role in the final morphology and efficacy of the imprinted film. In this work, various concentrations of poly(ethylene-co-vinyl alcohol) (EVAL) were dissolved in dimethyl sulfoxide (DMSO) for the microcontact imprinting of algae on an electrode. Scanning electron microscopy and fluorescence spectrometry were used to characterize the surface morphology and recognition capacity of algae to the algae-imprinted cavities. The readsorption of algae onto algae-imprinted EVAL thin films was quantified to obtain the EVAL concentration that maximized algal binding. Finally, the power and current density of an algal biofuel cell with the algae-imprinted EVAL-coated electrode were measured and found to be approximately double those of such a cell with a Pt/indium tin oxide (ITO)/poly(ethylene terephthalate) (PET) electrode.

Control of the release of curcumin from micelles by ultrasound

In this study, ultrasound was employed to control the release of curcumin entrapped in micelles. Stable micelles were formed in water from a mixture of surfactants (Tween 80 and lecithin in a 1:0.3 mole ratio) with ethyl oleate. The weight ratio of water:surfactants:oleate was 10:2.62:1. One mg of curcumin was solubilized in 4.67 mL of micelle solution. Under 40 kHz insonation from a probe sonicator, much of the curcumin was released from the micelles and formed insoluble aggregates, as evidenced by decreased UV-vis absorption at 420 nm. The initial release rate (assayed by the rate of absorption change) decreased at acidic pH, but was about 3.5 /spl mu/g/s (1.87 %/sec) in a PBS buffer at neutral or alkaline pH.

The encapsulation of curcumin in micelles

This report demonstrates the preparation of a curcumin-encapsulated microemulsion system by using biocompatible materials. In this study, ethyl oleate, lecithin and Tween80 were chosen as the oil phase and surfactants, respectively. The result indicated that when the mole ratio of Lecithin/Tween 80 was 0.3, the optimum capacity of oil solubility would reach 10.3% by weight. We also performed an in-vitro analysis for testing the stability of this microemulsion. Three days after diluted with deionized water, no aggregation or leakage were observed in the microemulsion system. These studies might be valuable for the development of microemulsion formulation in pharmaceutical industry.

Sensing lysozyme rebinding on molecularly imprinted polymers by scanning electrochemical microscopy

Molecularly imprinted polymers, artificial antibodies, were synthesized by printing target biomolecules on a monomer mixture and then forming a highly selective and stable polymer. Scanning electrochemical microscopy (SECM) was employed to measure the reduction current between horseradish peroxide (HRP) conjugated lysozyme antibody and ferrocenylmethol (FMA) after different lysozyme concentrations for rebinding were applied on the molecularly imprinted polymers. We found that the reduction current increased linearly with increasing the rebinding lysozyme concentration.

The recognition of lysozyme by patterned molecularly imprinted polymers

Microelectro-mechanical-system (MEMS) microsensing devices have recently been extensively researched for their application in biomedical diagnostics. Molecularly imprinted polymers with highly specific binding to targets and their low cost have potential for use in devices as sensing materials. Both techniques were combined to synthesize localized molecularly imprinted polymers (MIPs) by microcontact printing for integration in a micrototal analysis system (/spl mu/TAS).

Design of creatinine-imprinted polymers

Creatinine level in blood or urine is associated with human renal function. A high-affinity functional monomer with creatinine in preparing creatinine-imprinted polymer could be used to increase binding capacity and improve sensing with creatinine. The most absorptive functional monomer was methacrylic acid (MAA) and the functional monomer sequence was MAA>2-hydroxyethylmethacrylate (HEMA)>N-vinyl pyrrolidone (NVP)/spl Gt/4-vinyl pyridine (4VP). The selectivity of creatinine-imprinted polymer to creatine and uric acid, when MAA was used as the functional monomer, exceeded that obtained using HEMA as the functional monomer.