Water-in-water Emulsion Based Synthesis of Functional Poly(ethylene glycol) Microgels for Cell Targeting

Mohammadreza Mohammadi1, Caner Nazli1, Seda Kizilel1,2

1Koç University, Material Science and Engineering, Istanbul, 34450, Turkey

2Koç University, Chemical and Biological Engineering, Istanbul, 34450, Turkey

Microgels have emerged as promising platforms for controlled release and targeted delivery in tissue engineering. High surface area of microgels provides high conjugation density, size and shape tuneability, and agent loading potential, which have attracted the attention of many researchers. Several successful efforts have been devoted to synthesize microgels employing water-in-oil (w/o) emulsion. However, the presence of organic phase results in denaturation of loaded therapeutic molecule, or experimentally impractical. With this respect, eliminating the organic phase is an essential task which provides a safe environment for the synthesis of microgels, specifically for biomedical applications. Here, we used water-in-water (w/w) emulsion to synthesize bio-functional microgel via photopolymerization of Poly(ethylene glycol) diacrylate (PEG-DA). Microgels were fabricated under mild conditions, via green light illumination, within 25 seconds. These conditions would be desirable for loading of proteins or cells within the microgel structure during synthesis. Fluorescein bound microgels were functionalized with fibronectin-derived arginine-glycine-aspartic acid-serine (RGDS) peptide sequences for achieve specific cell-targeting property. Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM) were used for the characterization of size and morphology. Spherical particles with a size of 0.5 µm were obtained (Figure 1). Fourier Transform Infrared Spectroscopy (FTIR) was employed to confirm the presence of PEG- DA chains, and to characterize functional groups within the polymeric gel. Fluorescent microscope images demonstrated internalization of these particles by HeLa cells (Figure
2). These gels could also be designed as responsive, and could be an attractive option for triggered molecule release which would enable on-demand control of the dose and timing of the targeted therapeutic molecule.
Keywords; water-in-water emulsion, PEG microgel, RGDS, Cell Uptake, targeted drug delivery

Figure 1. Dynamic Light Scattering result of Microgel
(a) (b)

Figure 2. (a) Optical micrsocopy image of HeLa cells, (b) Fluorescence microscopy image of RGDS functionalized PEG microgels internalized in HeLa cells