NSFSTC Groupmeeting
Thursday, 23 April 2009, 3:00 - 5:00pm EST
 
Preamble:

We will start at 3:00pm, please be there on time!

Presenters:

Kirill Efimenko, NCSU

Formation of surface-grafted polymeric amphiphilic coatings comprising ethylene glycol and fluorinated groups and their response to protein adsorption

Amphiphilic polymer coatings have been formed by first generating surface-anchored polymer layers of poly(2-hydroxyethyl methacrylate) (PHEMA) on top of flat solid substrates followed by postpolymerization reaction on the hydroxyl terminus of HEMA’s pendent group using various fluorinating agents.  The extent of the fluorination inside the polymer brushes was assessed by means of a suite of analytical probes.  We have shown that distribution of fluorinated species and degree of fluorination inside the brush depends strongly on the nature of modifier and deposition conditions.  The surface activity of the amphiphilic coatings was tested by studying the adsorption of fibrinogen.

Justina Tam, UT-Austin

Biodegradable Gold-Polymer Nanoclusters for Near Infrared Imaging and Rapid Clearance

Nanotechnology holds great promise for molecular specific diagnostic and therapeutic strategies.  For such applications, nanoparticles (NP) must possess a high blood residence time to carry out its function, the ability to be broken down into biocompatible, renally clearable components, and high optical near-infrared (NIR) absorbance capabilities for in vivo imaging.  Current NIR absorbing nanoparticles are larger than 50 nm in diameter, which is above the threshold of 5 nm for rapid, efficient renal clearance.  Here, we present a sub-100 nm particle consisting of lysine capped 5 nm gold NP, clustered by a biodegradable tri-block copolymer of lactic acid and ethylene glycol, PLA(2K)-b- PEG(10K)-b-PLA(2K).  The gold NP cluster will provide high NIR absorbance due to the plasmon coupling effect of the closely spaced gold NP, while the polymer will provide degradability of the cluster into 5 nm gold components.  The polymer will degrade over time via hydrolysis at physiological pH, but will undergo accelerated degradation at a pH typically found in cellular endosomes, pH 5, as shown by absorbance spectrophotometry.  Degradation kinetics inside macrophage cells showed a similarly accelerated degradation effect, as shown by transmission electron and optical microscopy in parallel with hyperspectral imaging.  The general concept of hybrid polymer/metal nanoclusters for in vivo imaging and efficient clearance combines the advantages of the biodegradability of polymers and the strong optical contrast of gold nanoparticles.

Jin Wang, UNC

Cancer Cells Targeting with Transferrin Receptor Antibody

Transferrin receptor is an essential protein involved in iron uptake and regulation of cell growth. Many kinds of tumor cells overexpress transferrin receptors due to the necessity of large amount of iron to maintain rapid proliferation. The surface of PRINT nanoparticles (200 nm × 200 nm, cylindrical) was conjugated with mouse anti-human transferrin receptor monoclonal antibody (TfR mAb, clone number: OKT-9, mouse IgG1) using biotin-avidin technique. As shown in Figure 1, PRINT particles coated with TfR mAb (black bars) show promising targeting efficiency (63-98% of cell uptake) on seven human cancer cell lines employed in this study (HeLa, cervical carcinoma; Sup-B8, Burkitt’s B-cell lymphoma; Ramos, Burkitt’s B-cell lymphoma; H125, lung adenocarcinoma; SK-OV-3, ovarian adenocarcinoma; MGR3, human glioblastoma; LNCaP, prostate adenocarcinoma) compared with PRINT particles coated with TfR mAb isotype control IgG1 (red bars). Particles coated with anti-human TfR mAb OKT-9 or isotype control IgG1 show little uptake on mouse embryonic fibroblast (MEF), which was used as negative control cell line and does not bind OKT-9 or isotype control mouse IgG1 (data not shown). The fact that TfR mAb coated nanoparticles show specific uptake on human cancer cell lines and little uptake on a non-human cell line MEF suggests TfR-mediated cell uptake. Based on 72 hr MTS assays, the nanoparticles coated with TfR mAb or IgG1 show little cytotoxicity on all the eight cell lines employed in this study except Ramos cells. More than 80% of the Ramos cells were killed by TfR mAb coated nanoparticles at a concentration of 100 µg/mL. In contrast, free TfR mAb does not induce Ramos cell death. Ramos cell viability was also studied as a function of TfR mAb density on particle surface. There was a strong correlation between TfR ligand density on particle surface and cell viability. Investigations into the mechanism of cell death are underway. These TfR mAb coated PRINT particles are promising immunotherapeutic agents for B-cell lymphoma and a series of in vivo experiments have been planned.

Figure 1. Cell uptake of PRINT nanoparticles (100 µg/mL) conjugated with mouse anti-human transferrin receptor monoclonal antibody (TfR mAb, black bars) or isotype control IgG1 (negative control, red bars) in seven human cancer cell lines and one mouse embryonic fibroblast (MEF).

	If you are a presenter, please be in the videoconference room 15 to 20 minutes before the meetings starts so that you have enough time to download your presentation to the computer.
	Also: Place the microphone in the middle and as high as possible on your shirt (very important).
	Especially for UNC presenters: If you are talking with someone at UT-Austin or NCSU, do not look and speak to the large screens, look to the camera, otherwise we will just see the back of your head…
	Audience: Please do not (!) touch the microphones on the desk, do not play with them or brush with a pen or your fingers or any papers over them, this produces an annoying background noise to the other locations.
	Please say your name and location before you start giving a comment. Not everyone knows everyone and we always have some new students. In addition, this gives the camera operator in the control room time to move the camera to your face.
	Font size for PowerPoint presentation: at least 28 pixel or more (download our PowerPoint template at: http://www.nsfstc.unc.edu/startcollabo.htm).
	For more suggestions: http://www.nsfstc.unc.edu/startcollabo.htm