Electrospun nanofibers for 3-D cancer models, diagnostics, and therapy.

As one of the leading causes of global mortality, cancer has prompted extensive research and development to advance efficacious drug discovery, sustained drug delivery and improved sensitivity in diagnosis. Towards these applications, nanofibers synthesized by electrospinning have exhibited great clinical potential as a biomimetic tumor microenvironment model for drug screening, a controllable platform for localized, prolonged drug release for cancer therapy, and a highly sensitive cancer diagnostic tool for capture and isolation of circulating tumor cells in the bloodstream and for detection of cancer-associated biomarkers. This review provides an overview of applied nanofiber design with focus on versatile electrospinning fabrication techniques.

Crosslinked Chitosan-PEG Hydrogel for Culture of Human Glioblastoma Cell Spheroids and Drug Screening.

Two-dimensional monolayer cell cultures are routinely utilized for preclinical cancer drug screening, but the results often do not translate well when drugs are tested in vivo. To address this limitation, a biocompatible chitosan-PEG hydrogel (CSPG gel) was synthesized to create a gel that can be easily dispensed into 96-well plates at room temperature and neutral pH. The stiffness of this gel was tailored to be within the stiffness range of human glioblastoma tissue to promote the formation of tumor spheroids.

Chitosan-based composite bilayer scaffold as an in vitro osteochondral defect regeneration model.

Prolonged osteochondral tissue damage can result in osteoarthritis and decreased quality of life. Multiphasic scaffolds, where different layers model different microenvironments, are a promising treatment approach, yet stable joining between layers during fabrication remains challenging. Here, a bilayer scaffold for osteochondral tissue regeneration was fabricated using thermally-induced phase separation (TIPS).

Fabrication and Characterization of Chitosan-Hyaluronic Acid Scaffolds with Varying Stiffness for Glioblastoma Cell Culture.

The invasive and recurrent nature of glioblastoma multiforme (GBM) is linked to a small subpopulation of cancer cells, which are self-renewing, resistant to standard treatment regimens, and induce formation of new tumors. Matrix stiffness is implicated in the regulation of cell proliferation, drug resistance, and reversion to a more invasive phenotype. Therefore, understanding the relationship between matrix stiffness and tumor cell behavior is vital to develop appropriate in vitro tumor models.

Chitosan-Poly(caprolactone) Nanofibers for Skin Repair.

Dermal wounds, both acute and chronic, represent a significant clinical challenge and therefore the development of novel biomaterial-based skin substitutes to promote skin repair is essential. Nanofibers have garnered attention as materials to promote skin regeneration due to the similarities in morphology and dimensionality between nanofibers and native extracellular matrix proteins, which are critical in guiding cutaneous wound healing. Electrospun chitosan-poly(caprolactone) (CPCL) nanofiber scaffolds, which combine the important intrinsic biological properties of chitosan and the mechanical integrity and stability of PCL, were evaluated as skin tissue engineering scaffolds using a mouse cutaneous excisional skin defect model.

PEG-chitosan hydrogel with tunable stiffness for study of drug response of breast cancer cells.

Mechanical properties of the extracellular matrix have a profound effect on the behavior of anchorage-dependent cells. However, the mechanisms that define the effects of matrix stiffness on cell behavior remains unclear. Therefore, the development and fabrication of synthetic matrices with well-defined stiffness is invaluable for studying the interactions of cells with their biophysical microenvironment .

Modeling the tumor microenvironment using chitosan-alginate scaffolds to control the stem-like state of glioblastoma cells.

Better prediction of in vivo drug efficacy using in vitro models should greatly improve in vivo success. Here we utilize 3D highly porous chitosan-alginate complex scaffolds to probe how various components of the glioblastoma microenvironment including extracellular matrix and stromal cells affect tumor cell stem-like state.

High-throughput and high-yield fabrication of uniaxially-aligned chitosan-based nanofibers by centrifugal electrospinning.

The inability to produce large quantities of nanofibers has been a primary obstacle in advancement and commercialization of electrospinning technologies, especially when aligned nanofibers are desired. Here, we present a high-throughput centrifugal electrospinning (HTP-CES) system capable of producing a large number of highly-aligned nanofiber samples with high-yield and tunable diameters. The versatility of the design was revealed when bead-less nanofibers were produced from copolymer chitosan/polycaprolactone (C-PCL) solutions despite variations in polymer blend composition or spinneret needle gauge.

Chitosan-PEG hydrogel with sol-gel transition triggerable by multiple external stimuli.

Smart hydrogels play an increasingly important role in biomedical applications, since materials that are both biocompatible and multi-stimuli-responsive are highly desirable. A simple, organic solvent-free method is presented to synthesize a biocompatible hydrogel that undergoes a sol-gel transition in response to multiple stimuli. Methoxy-poly(ethylene glycol) (mPEG) is modified into carboxylic-acid-terminated-methoxy-poly(ethylene glycol) (mPEG-acid), which is then grafted onto chitosan via amide linkages yielding mPEG-g-chitosan.

Chitosan-based scaffolds for bone tissue engineering.

Bone defects requiring grafts to promote healing are frequently occurring and costly problems in health care. Chitosan, a biodegradable, naturally occurring polymer, has drawn considerable attention in recent years as scaffolding material in tissue engineering and regenerative medicine. Chitosan is especially attractive as a bone scaffold material because it supports the attachment and proliferation of osteoblast cells as well as formation of mineralized bone matrix.

High affinity binding of an engineered, modular peptide to bone tissue.

Bone grafting procedures have become common due in part to a global trend of population aging. Native bone graft is a popular choice when compared to various synthetic bone graft substitutes, owing to superior biological activity. Nonetheless, the insufficient ability of bone allograft to induce new bone formation and the insufficient remodeling of native bone grafts call for osteoinductive factors during bone repair, exemplified by recombinant human bone morphogenetic protein 2 (rhBMP2).

Regulating specific growth factor signaling using immobilized branched ligands.

VEGF-binding peptide ligands are incorporated into hydrogel microspheres and reduce the amount of growth factor in solution. VEGF binding affinity is enhanced by creating ligands with a dimer structure. The spheres are able to knock down VEGF-mediated HUVEC growth and reduce calcium signaling.

Extending foldamer design beyond α-helix mimicry: α/β-peptide inhibitors of vascular endothelial growth factor signaling.

Diverse strategies have been explored to mimic the surface displayed by an α-helical segment of a protein, with the goal of creating inhibitors of helix-mediated protein-protein interactions. Many recognition surfaces on proteins, however, are topologically more complex and less regular than a single α-helix. We describe efforts to develop peptidic foldamers that bind to the irregular receptor-recognition surface of vascular endothelial growth factor (VEGF).

Specific VEGF sequestering and release using peptide-functionalized hydrogel microspheres.

Growth factor signaling plays an essential role in regulating processes such as tissue development, maintenance, and repair. Gene expression levels, diffusion, degradation, and sequestration by extracellular matrix components all play a role in regulating the concentration of growth factors within the cellular microenvironment. Herein, we describe the synthesis and characterization of hydrogel microspheres that mimic the ability of the native extracellular matrix to reversibly bind vascular endothelial growth factor (VEGF) out of solution.

Mineral coatings modulate β-TCP stability and enable growth factor binding and release.

β-Tricalcium phosphate (β-TCP) is an attractive ceramic for bone tissue repair because of its similar composition to bone mineral and its osteoconductivity. However, compared with other ceramics β-TCP has a rapid and uncontrolled rate of degradation. In the current study β-TCP granules were mineral coated with the aim of influencing the dissolution rate of β-TCP, and also to use the coating as a carrier for controlled release of the growth factors recombinant human vascular endothelial growth factor (rhVEGF), modular VEGF peptide (mVEGF), and modular bone morphogenetic protein 2 peptide (mBMP2).

Biomaterials for high-throughput stem cell culture.

A cell's microenvironment plays a primary role in defining cell fate during tissue development, physiological function, and pathological dysfunction. Understanding the key components and interactions within these microenvironments is critical for effective use of stem cells for disease modeling and therapeutic applications. Yet cell microenvironments are difficult to study, as there are tens or hundreds of parameters that can influence cell behavior simultaneously.

The effect of BMP-2 on micro- and macroscale osteointegration of biphasic calcium phosphate scaffolds with multiscale porosity.

It is well established that scaffolds for applications in bone tissue engineering require interconnected pores on the order of 100 microm for bone in growth and nutrient and waste transport. As a result, most studies have focused on scaffold macroporosity (>100 microm). More recently researchers have investigated the role of microporosity in calcium phosphate -based scaffolds.

Multiscale osteointegration as a new paradigm for the design of calcium phosphate scaffolds for bone regeneration.

The role of macropore size (>100 microm) and geometry in synthetic scaffolds for bone regeneration has been studied extensively, but successful translation to the clinic has been slow. Significantly less attention has been given to porosity at the microscale (0.5-10 microm).