Nanofibers of Elastin and Hydrophilic Segmented Polyurethane Solution Blends Show Enhanced Mechanical Properties through Intermolecular Protein–Polymer H Bonding

Combining mechanical properties with enhanced cell interaction is highly desirable in a biomaterial. In this study, a new paradigm for enhancing the mechanical properties of segmented polyurethanes (SPUs) through solution blending with a biopolymer is presented. This noncovalent approach is based on the premise that molecular level blending of SPUs rich in hydrogen bonding (H bonding) domains with a biopolymer capable of H bonding will promote H-bond bridges between the components, leading to molecular annealing and modification of the physicochemical properties of the SPU. We demonstrate that by solution-blending solubilized elastin with a triblock copolymer-derived SPU, a 5-fold increase in tensile modulus of electrospun constructs of the SPU can be achieved, with concomitant enhancement in human endothelial cell attachment. Spectroscopic and calorimetric analysis confirm the role of H bonding in the enhancement, thus providing the impetus to further explore blending with biopolymers as a means of improving the property profiles of synthetic polymeric biomaterials

<i>In vivo</i> imaging and visualization of tumor mass and vasculature.

<p>(A) FT 3D reconstructed volumes of a rat bearing a MDA-E2 tumor (green) and the associated vasculature (red) visualized using AngioSense. Bar indicates 4.1 μm. (B) <i>Ex vivo</i> reflectance images of the corresponding tumor in (A). Bar indicates 4.1 μm. (C) Representative histological images of the tumor in (A) and (B) stained with antibodies against CD31 (red) and human nuclei (green). The nuclei were stained with DAPI (blue). The tumor mass is marked with (*) and the surrounding vascularized host stroma with (^). Bar indicates 100 μm.</p

<i>In vivo</i> detection of tumors in the lung.

<p>(A) Co-registration of FT and μCT data sets 36 days after tumor cell injection. Light gray indicates fluorescence signal detected by FT, skeletal structures were visualized by μCT and are colored red. (B) E<i>x vivo</i> reflectance image of the corresponding lung. (C) Representative histological image of the lung tissue with antibodies against CD31 (red) and human nuclei (green). The nuclei were stained with DAPI (blue). Clusters of human tumor cells are marked with (*).Bar indicates 100 μm.</p

Long-term detection of MDA-E2 cells <i>in vivo</i>.

<p>(A) MDA-E2 or MDA-WT tumor cells were injected in the flank of nude rats and the tumor size was measured using calipers. n = 5–6. (B) Rats bearing MDA-E2 tumors were scanned with FT. Left axis fluorescence intensity (black triangles) and right axis tumor volume (grey squares) measured using calipers. n = 6. All data is represented as mean ± standard deviation.</p

<i>In vitro</i> analysis of cell lines expressing E2-Crimson.

<p>The fluorescence intensity of various amounts of (A) MDA-E2, (B) HeLa-E2 and (C) A594-E2 cells, were measured in optical phantoms using FT. Non transduced parental cell lines (denoted with WT) were only measured at a concentration of 10⁶ cells. (D-F) Cell viability and (G-I) migratory potential was compared between E2-Crimson expressing cells and the wild-type parental cell lines. All data is represented as mean ± standard deviation. Significance was measured by Students t test. n = 3.</p

Clickable Degradable Aliphatic Polyesters via Copolymerization with Alkyne Epoxy Esters: Synthesis and Postfunctionalization with Organic Dyes

Degradable aliphatic polyesters are the cornerstones of nanoparticle (NP)-based therapeutics. In this paradigm, covalent modification of the NP with cell-targeting motifs and dyes can aid in guiding the NP to its destination and gaining visual confirmation. Therefore, strategies to impart chemistries along the polymer backbone that are amenable to easy modification, such as 1,3-dipolar cycloaddition of an azide to an alkyne (the “click reaction”), could be significant. Here we present a simple and efficient way to introduce alkyne groups at high density in aliphatic polyesters without compromising their crystallinity via the copolymerization of cyclic lactones with propargyl 3-methylpentenoate oxide (PMPO). Copolymers of lactic acid and ε-caprolactone with PMPO were synthesized with up to 9 mol % alkyne content, and accessibility of the alkyne groups to the click reaction was demonstrated using several dyes commonly employed in fluorescence microscopy and imaging (Cy3, ATTO-740, and coumarin 343). In order to establish the suitability of these copolymers as nanocarriers, copolymers were formulated into NPs, and cytocompatibility, cellular uptake, and visualization studies undertaken in HeLa cells. Dye-modified NPs exhibited no quenching, remained stable in solution for at least 10 days, showed no cytotoxicity, and were readily taken up by HeLa cells. Furthermore, in addition to enabling the incorporation of multiple fluorophores within the same NP through blending of individual dye-modified copolymers, dye-modified polyesters offer advantages over physical entrapment of dye, including improved signal to noise ratio and localization of the fluorescence signal within cells, and possess the necessary prerequisites for drug delivery and imaging

Overview of the key properties of poly(CL-<i>co</i>-OEG-MPO) copolymers.

<p>MPO: 2-methyl-4-pentenoate oxide; 1EG-MPO: 2-ethoxyethanol-MPO; 3EG-MPO: trimethylene glycol monomethyl ether-MPO; 12EG-MPO: poly(ethylene glycol) monomethyl ether-MPO.</p

Fluorescence images of MC3T3-E1 cells on poly(CL-<i>co</i>-OEG-MPO) copolymer films.

<p>Green: F-actin stress fibers; blue: nucleus. Note the change in cell morphology from a highly anisotropic cell morphology on unmodified PCL and low oligo-EG-PCL surfaces to a more isotropic (rounded) morphology on poly(CL-co-3EG-MPO) with 8% incorporation.</p

Static water contact angle of poly(CL-<i>co</i>-OEG-MPO) copolymers.

<p>Static water contact angle of poly(CL-<i>co</i>-OEG-MPO) copolymers.</p

Summary of the thermal properties of poly(CL-<i>co</i>-OEG-MPO) copolymers.

<p>MPO: 2-methyl-4-pentenoate oxide; 1EG-MPO: 2-ethoxyethanol-MPO; 3EG-MPO: trimethylene glycol monomethyl ether-MPO; 12EG-MPO: poly(ethylene glycol) monomethyl ether-MPO.</p