In Vitro Biocompatibility of Surface-Modified Porous Alumina Particles for HepG2 Tumor Cells: Toward Early Diagnosis and Targeted Treatment.

Porous alumina photoluminescence-inherent particles are produced and proposed for the development of biomarkers detectors and localized treatment of HepG2 cells. Nanoporous alumina particles (NPAPs) are amorphous, consist of hexagonally ordered nanometric pores in an alumina matrix, have high chemical stability in physiological pH, and exhibit a high inherent photoluminescence in the visible spectrum independently of their size, selectable from nanometers to tens of micrometers. The surface of NPAPs is chemically modified using two different functionalization methods, a multistep method with (3-aminopropyl)triethoxysilane (APTES) and glutaraldehyde (GLTA) and a novel simplified-step method with silane-PEG-NHS. Fourier Transform infrared spectroscopy analysis confirmed the proper surface modification of the particles for both functionalization methods. HepG2 cells were cultured during different times with growing concentrations of particles. The analysis of cytotoxicity and cell viability of HepG2 cells confirmed the good biocompatibility of NPAPs in all culture conditions. The results prove the suitability of NPAPs for developing new label-free biomarker detectors and advantageous carriers for localized drug delivery.

Protein attachment to nanoporous anodic alumina for biotechnological applications: influence of pore size, protein size and functionalization path.

Nanoporous anodic alumina (NAA) is a material with great interest in nanotechnology and with promising applications to biotechnology. Obtaining specific and regularly functionalized NAA surfaces is essential to obtain meaningful results and applications. Silane-PEG-NHS (triethoxysilane-polyethylene-glycol-N-hydroxysuccinimide) is a covalent linker commonly used for single-molecule studies. We investigate the functionalization of NAA with silane-PEG-NHS and compared with two common, but not single-molecule, grafting agents, APTMS (3-aminopropylotrimethoxysilane) as an electrostatic linker, and APTMS-GTA (3-aminopropylotrimethoxysilane-glutaraldehyde) as covalent. Another outcome of this study is to show how two proteins (collagen and bovine serum albumin, BSA) with different properties differentially arrange for different functionalizations and NAA pore sizes. FTIR is used to demonstrate the surface modification steps and fluorescence confocal microscopy reveals that silane-PEG-NHS results in a more homogeneous protein distribution in comparison to the other linkers. Reflection interference Fourier transform spectroscopy confirms the confocal fluorescence microscopy results and permits to estimate the amounts of linker and linked proteins within the pores. These results permit to obtain uniformly chemical modified NAA supports with a great value in biosensing, drug delivery and cell biology.

Isolation and Characterization of Adhesive Secretion from Cuvierian Tubules of Sea Cucumber Holothuria forskåli (Echinodermata: Holothuroidea).

The sea cucumber Holothuria forskåli possesses a specialized system called Cuvierian tubules. During mechanical stimulation white filaments (tubules) are expelled and become sticky upon contact with any object. We isolated a protein with adhesive properties from protein extracts of Cuvierian tubules from H. forskåli. This protein was identified by antibodies against recombinant precollagen D which is located in the byssal threads of the mussel Mytilus galloprovincialis. To find out the optimal procedure for extraction and purification, the identified protein was isolated by several methods, including electroelution, binding to glass beads, immunoprecipitation, and gel filtration. Antibodies raised against the isolated protein were used for localization of the adhesive protein in Cuvierian tubules. Immunostaining and immunogold electron microscopical studies revealed the strongest immunoreactivity in the mesothelium; this tissue layer is involved in adhesion. Adhesion of Cuvierian tubule extracts was measured on the surface of various materials. The extracted protein showed the strongest adhesion to Teflon surface. Increased adhesion was observed in the presence of potassium and EDTA, while cadmium caused a decrease in adhesion. Addition of antibodies and trypsin abolished the adhesive properties of the extract.