Microfabricated electrospun collagen membranes for 3-D cancer models and drug screening applications.

Invasive epithelial tumors form from cells that are released from their natural basement membrane and form 3-D structures that interact with each other and with the microenvironment of the stromal tissues around the tumor, which often contains collagen. Cancer cells, growing as monolayers on tissue culture plastic, do not reflect many of the properties of whole tumors. This shortcoming limits their ability to serve as models for testing of pharmacologically active compounds, including those that are being tested as antineoplastics. This work seeks to create new 3-D cellular materials possessing properties similar to those in native tissues surrounding cancers, specifically electrospun micro- and nanofibrous collagen scaffolds that support tumor growth in 3-D. We hypothesize that a 3-D culture system will provide a better replica of tumor growth in a native environment and, thus, better report the bioactivity of antineoplastic agents. In addition, we optimized conditions and identified physical characteristics that support growth of the highly invasive, prostate cancer bone metastatic cell line C4-2B on these matrices for use in anticancer drug studies. The effects of matrix porosity, fiber diameter, elasticity, and surface roughness on growth of cancer cells were evaluated. Data indicates that while cells attach and grow well on both nano- and microfibrous electrospun membranes, the microfibrous membrane represented a better approximation of the tumor microenvironment. It was also observed that C4-2B nonadherent cells migrated through the depth of two electrospun membranes and formed colonies resembling tumors on day 3. An apoptosis study revealed that cells on electrospun substrates were more resistant to both antineoplastic agents, docetaxel (DOC), and camptothecin (CAM) compared to the cells grown on standard collagen-coated tissue culture polystyrene (TCP). Growth, survival, and apoptosis were measured, as well as the differences in the apoptotic capabilities, of the two above-mentioned compounds compared to known clinical performance. We conclude that 3-D electrospun membranes are amenable to high throughput screening for cancer cell susceptibility and combination killing (Banerjee, S.; Hussain, M.; Wang, Z.; Saliganan, A.; Che, M.; Bonfil, D.; Cher, M.; Sarkar, F.H. Cancer Research, 2007, 67 (8), 3818-26).

Bottom-up synthesis of anatase nanoparticles with graphene domains.

Using alizarin and titanium isopropoxide, we have succeeded in preparing a hybrid form of nanostructured graphene-TiO2 following a bottom-up synthetic approach. This novel graphene-based composite offers a practical alternative to synthesizing photocatalytically active materials with maximized graphene-TiO2 interface. The molecular precursor alizarin was chosen because it efficiently binds to TiO2 through the hydroxyl groups and already possesses the graphene building block through its anthracene basis. XPS and Raman spectroscopy proved that the calcined material contained majority sp(2)-hybridized carbon that formed graphene-like clusters. XRD data showed the integrated structures maintained their anatase crystallography, therefore preserving the material's properties without going through phase transitions to rutile. The enhanced graphene and TiO2 interface was confirmed using DFT computational techniques. The photocatalytic activity of the graphene-TiO2 materials was demonstrated through degradation of methylene blue.

Biofunctionalization of electrospun PCL-based scaffolds with perlecan domain IV peptide to create a 3-D pharmacokinetic cancer model.

Because prostate cancer cells metastasize to bone and exhibit osteoblastic features (osteomimicry), the interrelationships between bone-specific microenvironment and prostate cancer cells at sites of bone metastasis are critical to disease progression. In this work the bone marrow microenvironment in vitro was recreated both by tailoring scaffolds physical properties and by functionalizing electrospun polymer fibers with a bioactive peptide derived from domain IV of perlecan heparan sulfate proteoglycan. Electrospun poly (epsilon-caprolactone) (PCL) fibers and PCL/gelatin composite scaffolds were modified covalently with perlecan domain IV (PlnDIV) peptide. The expression of tight junction protein (E-cadherin) and focal adhesion kinase (FAK) phosphorylation on tyrosine 397 also were investigated. The described bioactive motif significantly enhanced adherence and infiltration of the metastatic prostate cancer cells on all modified electrospun substrates by day 5 post-seeding. Cells cultured on PlnDIV-modified matrices organized stress fibers and increased proliferation at statistically significant rates. Additional findings suggest that presence of PlnDIV peptide in the matrix reduced expression of tight junction protein and binding to PlnDIV peptide was accompanied by increased focal adhesion kinase (FAK) phosphorylation on tyrosine 397. We conclude that PlnDIV peptide supports key signaling events leading to proliferation, survival, and migration of C4-2B cancer cells; hence its incorporation into electrospun matrix is a key improvement to create a successful three-dimensional (3-D) pharmacokinetic cancer model.