Modular scaffolds assembled around living cells using poly(ethylene glycol) microspheres with macroporation via a non-cytotoxic porogen

Abstract

Modular, bioactive, macroporous scaffolds were formed by crosslinking poly(ethylene glycol) (PEG) microspheres around living cells. Hydrogel microspheres were produced from reactive PEG derivatives in aqueous sodium sulfate solutions without the use of surfactants or copolymers. Microspheres were formed following thermally induced phase separation if the gel point was reached prior to extensive coarsening of the PEG-rich domains. Three types of PEG microspheres with different functionalities were used to form scaffolds. One type of PEG microsphere provided mechanical support, the second type provided controlled delivery of the angiogenesis-promoting molecule, sphingosine 1-phosphate (S1P), and the third type served as a slowly dissolving noncytotoxic porogen. Scaffolds were formed by centrifuging microspheres in the presence of HepG2 hepatoma cells, resulting in a homogenous distribution of cells. During overnight incubation at 37°C, the microspheres reacted with serum proteins in cell culture medium to stabilize the scaffolds. Within two days in culture, macropores formed due to the dissolution of the porogenic PEG microspheres, without affecting cell viability. Gradients in porosity were produced by varying the buoyancy of the porogenic microspheres. Conjugated RGD cell adhesion peptides and delivery of sphingosine 1-phosphate promoted endothelial cell infiltration through macropores in the scaffolds. The scaffolds presented here differ from previous hydrogel scaffolds in that: 1) cells are not encapsulated in hydrogel, 2) macropores form in the presence of cells, and 3) scaffold properties are controlled by the modular assembly of different microspheres that perform distinct functions.

The Effect of Melatonin Adsorbed to Polyethylene Glycol Microspheres on the Survival of MCF-7 Cells

“…The microspheres were obtained from PEG 6000 using a modification [18,19] of a previously described protocol [3]. Briefly, 20 g of PEG 6000 was resuspended in 100 ml of a 2% sodium sulfate solution in phosphate-buffered saline (PBS) and incubated at 37°C for 45 min.…”

“…The adsorption capacity of the microspheres can be modified to improve the biological function of the organic compounds transported [3]. In an earlier study, we showed that PEG microspheres are a promising carrier for melatonin because they prevent the degradation of this hormone and increase its bioavailability, improving the immune response of the organism [4].…”

Synthetic PEG Hydrogels as Extracellular Matrix Mimics for Tissue Engineering Applications

“…Using this technique, PEG hydrogels containing gradients with either sharp interfaces or gradual transitions with up to 5 distinct layers were formed. This approach has been also used to fabricate macroporous PEG hydrogels with gradients in porosity and homogeneously distributed PEG microspheres loaded with RGD and sphingosine 1-phosphate that promoted endothelial cell infiltration through the scaffolds, but the effects of gradients on cell behavior have yet to be determined (Scott et al, 2010). This technique offers the potential for incorporating gradients of biofunctionality or even regions of different proteins/drugs that are capable of diffusing from a microsphere of a particular density and stimulating a desired cellular response.…”

Polyethyleneglycol nanoparticles adsorbed to glycine as a bioengineered neomaterial for application in inflammatory processes

“…PH = 6.8 using a modification of the described method [18,19,20]. For the synthesis of polyethylene glycol (PEG) nanoparticles (NP-PEG) with glycine adsorbed for the complex formation (NANO-PEG/GLY) PEG 6000 (10g) at the concentration of 0.016 mol/L, was diluted in 100 mL of phosphate buffered saline (PBS), incubated for 45 min at 45ºC.…”

“…Previous work showed that the adsorption of glycine onto Polyethylene glycol (PEG) microsphere was able to stimulate the colostrum macrophages and suggest that the controlled delivery system of glycine may be an additional mechanism of protection and treatment of patients with infections and/or inflammation gastrointestinais, as well as for the functioning of colostrum cells [7]. Considering that the PEG is a biodegradable and biocompatible component [14] and that this particles have the capacity not to be recognized by the immune system, circulate for longer periods in the body [15,16,17] ] and has the ability to adsorb organic compounds, it is possible that this carrier of biological components to be used in the treatment of gastrointestinal inflammation [7,18,19,20]. The aim of this study was to evaluate the efficiency of the synthesis of polyethylene glycol (PEG) nanoparticles adsorbed with glycine (NANO-PEG/GLY) on functional activity of colostrum macrophages.…”