Zhengbao Zha

Fabrication of gelatin nanofibrous scaffolds using ethanol/phosphate buffer saline as a benign solvent

Electrospinning of natural polymer nanofibers useful for biomedical applications often requires the use of cytotoxic organic solvents. In this study, gelatin nanofibers are electrospun from phosphate buffer saline/ethanol binary mixtures as a benign solvent at ambient temperature. The influences of ionic strength, ethanol concentration, and gelatin concentration on the electrospinnability of gelatin solutions and the fiber microarchitectures are analyzed. The electrospun scaffolds retain their morphologies during vapor-phase crosslinking with glutaraldehyde in ethanol and the subsequent removal of salts contained in the nanofibers via water rinsing. When fully hydrated, the mechanically preconditioned scaffolds display a Youngs modulus of 25.5 ± 5.3 kPa, tensile strength of 55.5 ± 13.9 kPa, deformability of 160 ± 15%, and resilience of 89.9 ± 1.8%. When cultured on the gelatin scaffolds, 3T3 fibroblasts displayed spindle-like morphology, similar to the cells normal morphology in a 3D extracellular matrix.

Nanofibrous lipid membranes capable of functionally immobilizing antibodies and capturing specific cells.

Lipid bilayers that define the boundaries of cells and regulate intra/extracellular trafficking of ions and proteins have been a source of inspiration for the development of biomimetic materials. [1] For instance, liposomes have been extensively explored as carriers for drug delivery. [2] Furthermore, lipid membranes have been used as templates for the assembly of receptor signaling complexes [3] and the in vitro immunological study of cellular receptors. [4] Recently, electrospinning has been employed to engineer three-dimensional, high-surface-area lipid membranes composed of micrometer-diameter lecithin fibers. [5] Such lipid membranes may find important applications in biosensing and tissue engineering, but their poor durability adversely affect these potential applications. [6] Efforts to improve the material stability of phospholipid membranes, by polymerizing the lipids or incorporating additives, have been met with limited success. [6,7]

Organic-inorganic nanovesicles for doxorubicin storage and release

The potential of organic–inorganic liposomal cerasomes to store and release doxorubicin (DOX) is investigated. Specifically, cerasomes display sustained DOX release in serum-enriched cell culture medium but minimal drug leakage in deionized water. As revealed by a physics-based model, the medium-sensitive DOX release/leakage is attributed to serum-mediated dissociation of DOX molecules. DOX-loaded cerasomes effectively inhibit the proliferation of human prostate cancer DU145 cells. Furthermore, the kinetics of cerasome uptake/internalization and DOX release correlates well with the time scale for DOX-loaded cerasomes to inhibit the proliferation of the DU145 cells.

Atomic force microscopy of electrospun organic-inorganic lipid nanofibers

An organic-inorganic hybridization strategy has been proposed to synthesize polymerizable lipid-based materials for the creation of highly stable lipid-mimetic nanostructures. We employ atomic force microscopy (AFM) to analyze the surface morphology and mechanical property of electrospun cholesteryl-succinyl silane (CSS) nanofibers. The AFM nanoindentation of the CSS nanofibers reveals elastic moduli of 55.3 ± 27.6 to 70.8 ± 35 MPa, which is significantly higher than the moduli of natural phospholipids and cholesterols. The study shows that organic-inorganic hybridization is useful in the design of highly stable lipid-based materials.

Centering of organic-inorganic hybrid liposomal cerasomes in electrospun gelatin nanofibers

A study investigating the embedding of stabilized organic-inorganic liposomal cerasomes in gelatin nanofibers through the electrospinning of cerasome-dispersed gelatin aqueous solution is presented. Fluorescent and transmission electron microscopy confirm the embedding and centering of cerasomes in the electrospun nanofibers. A simple mechanism is proposed for the centering of cerasomes in gelatin nanofibers. The ability to incorporate cerasomes capable of encapsulating a variety of bioactive molecules provides a promising method to functionalize polymer nanofibers.

A biomimetic mechanism for antibody immobilization on lipid nanofibers for cell capture.

The immobilization of membrane-bound molecules on organic-inorganic cholesteryl-succinyl silane (CSS) nanofibers is investigated. Fluorescent microscopy and a cell capture assay confirm the stable and functional immobilization of membrane-bound antibodies and imaging agents on the electrospun CSS nanofibers. An insert-and-tighten mechanism is proposed for the observed hydration-induced reduction in lipid nanofiber diameter, the immobilization of membrane-bound molecules, and the improved efficiency of cell capture by the functionalized CSS nanofibers over their film counterparts. The ability to stably and functionally immobilize membrane-bound molecules on the CSS nanofibers presents a promising method to functionalize lipid-based nanomaterials.

Anti-EGFR antibody conjugated organic–inorganic hybrid lipid nanovesicles selectively target tumor cells

Chemical conjugation of anti-epidermal growth factor receptor monoclonal antibodies (anti-EGFR mAbs) to organic-inorganic hybrid liposomal immunocerasomes via maleimide-thiol coupling chemistry is explored as a mechanism for selectively targeting cancer cells. The cellular uptake and internalization of immunocerasomes are investigated in A431 cells that express an abnormally high level of EGFR, DU145 cells that overexpress EGFR, and HL-60 cells that are used as a negative control. The internalization study reveals a strong correlation between the receptor-mediated endocytosis of immunocerasomes and the membrane expression of EGFR. Further, free anti-EGFR mAbs and immunocerasomes conjugated with anti-EGFR mAbs at nanomolar doses display similar anti-proliferative effects on A431 cells. Additionally, serum proteins greatly reduce the cellular uptake of cerasomes that is mediated by non-specific receptors, but have no adverse effects on the specific EGFR-mediated delivery of immunocerasomes to A431 cells.

Comparative study of antibody immobilization mediated by lipid and polymer fibers

Antibody immobilization and function retention are important to a variety of applications, including proteomics, drug discovery, diagnostics, and biosensors. The present study investigates antibody immobilization mediated by cholesteryl succinyl silane (CSS) fibers, in comparison to hydrophobic polycaprolactone (PCL) fibers and hydrophilic plasma-treated PCL fibers. When incubated with a model protein, the formation of protein aggregates is observed on hydrophobic PCL fibers but not on the more hydrophobic CSS fibers, indicating that CSS fibers immobilize proteins through mechanisms other than hydrophobic interaction. When exposed to a limited amount of antibody, CSS fibers immobilize more antibodies than plasma-treated PCL fibers and no fewer antibodies than PCL fibers. The function retention of antibodies immobilized on the fibers is analyzed using a cell-capture assay, which shows that the antibody-functionalized CSS fibrous matrices capture 6- or 7-fold more cells than the antibody-functionalized PCL or plasma-treated PCL fibrous matrices, respectively. Data collected from the study show that the lipid fiber-mediated immobilization of antibody not only maintains the advantages of physical immobilization such as easiness and rapidness of operation but also improves function retention.

Functionalization of ceramic liposomal nanoparticles, cerasomes, with antibodies

Ceramic liposomal nanoparticles, cerasomes, are functionalized with antibodies on their surfaces that act as targeting ligands. This is achieved by using the siloxane network present on the cerasome surface as the foundation for chemical treatment processes previously developed for silicon surfaces. The bio-functionality and physical integrity of the cerasomes are characterized demonstrating successful immobilization of antibodies on the cerasome surface. The surface functionalization allows the cerasomes to deliver drugs to targeted cells expressing certain types of receptors with desired selectivity and specificity, which are not possible using standard liposomes.

Functionalization of Ceramic Liposomal Nanoparticles, Cerasomes, with Antibodies

Ceramic nanoparticles and silica microparticles are functionalized with antibodies on their surfaces that act as targeting ligands. For the ceramic liposomal nanoparticles, cerasomes, this is achieved by using the siloxane network present on the cerasome surface as the foundation for chemical treatment processes previously developed for silicon surfaces. The bio-functionality and physical integrity of the cerasomes are characterized, demonstrating successful immobilization of antibodies on the cerasome surface. The surface functionalization allows the cerasomes to deliver drugs to targeted cells expressing certain types of receptors with desired selectivity and specificity that are not possible using standard liposomes. The Silica microparticles are used to mimic cerasomes in experiments targeting cancer cells and the particle-cell specific binding due to the bio-functionalization process is demonstrated.