Biomedical subjects

Jeffery L Coffer

Publications and source records attributed to Jeffery L Coffer.

8 recordsLinked to original sources

PubMed2006

Biomineralization of calcium disilicide in porous polycaprolactone scaffolds.

The incorporation of CaSi(2) grains within a polycaprolactone (PCL) framework results in bioactive and biodegradable scaffolds which may be used in bone tissue regeneration. Porous PCL scaffolds were prepared via a combination of salt-leaching and microemulsion methods. To provide markedly different structural environments for the inorganic phase, calcium disilicide powder was either added to a mixed-composition porogen during a given scaffold preparation, or alternatively added to pre-formed scaffolds. Selective fluorescent labeling, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis were employed to assess scaffold calcification in vitro. The process of CaSi(2)/PCL scaffold calcification under zero bias, during which calcium phosphate growth is significantly dependent on the structural degradation of CaSi(2) grains, has a similar mechanism as the calcium phosphate growth on bioactive glasses/ceramics. The biomineralization of these scaffolds is initiated solely by the silicide phase and can be accelerated by the degradation of the polymer matrix.

Body Fluids↗

PubMed2006

Bias-assisted in vitro calcification of calcium disilicide growth layers on spark-processed silicon.

A dry-etch spark ablation method was used to produce calcium disilicide (CaSi2/Si) layers on silicon (Si) surfaces for the electrochemical growth of apatitic phosphates (calcium phosphate, CaP). CaSi2/Si composite electrodes readily calcify in vitro under the application of a small electric potential, and with proper treatment, the electrodeposition of CaP is localized to the sparked areas. In addition to increasing the local concentration of calcium, interfacial layers of CaSi2 on Si exhibit exceptional site selectivity towards CaP formation under bias due to the difference in conductivity between Si and CaSi2. The proposed mechanism for bias-assisted biomineralization of CaSi2/Si layers on spark-processed Si accounts for the physicochemical properties of deposited CaP films. This work also describes routes to surface modification of calcified composite electrodes with medicinally relevant compounds such as alendronate and norfloxacin. To assess the suitability of this material as a drug-delivery platform, release of the latter compound was also monitored as a function of time.

Anti-Infective Agents↗

PubMed2006

Biorelevant mesoporous silicon / polymer composites: directed assembly, disassembly, and controlled release.

We describe in this account a general, yet facile strategy for the directed assembly of bioactive composite materials comprised of an erodible organic polymer such as polycaprolactone and physiologically-resorbable inorganic mesoporous silicon. This method exploits a combination of capillary forces and selective interfacial coupling chemistry to produce isolable macroscale (mm sized) structures possessing a diverse range of geometries through simple mixing rather than intricate molding processes. Furthermore, we demonstrate the ability of such constructs to dissociate into their individual building blocks, with the concomitant release of embedded model compounds in a sustained manner.

Absorption↗

PubMed2006

Electronically-responsive delivery from a calcified mesoporous silicon structure.

The controlled release of substances from a semiconducting calcium phosphate/porous Si structure is reported. This is demonstrated principally for the case of the reversible adsorption and release of dyes (such as an anionic salt of fluorescein) upon the switching of the direction of bias to the underlying porous Si/Si substrate. The effect of bias on the diffusion of the cationic dyes ethidium bromide and acridine orange has also been investigated. For these species, their delivery can be mediated in part by the use of a surface layer of the biodegradable polymer poly-caprolactone (PCL).

Biocompatible Materials↗

PubMed2005

Nanostructured DNA templates.

We have developed methods for nanostructure fabrication relying on the size and shape of a polynucleotide to dictate the overall structure of an assemblage of individual semiconductor nanoparticles. Use of the circular plasmids pUCLeu4 and phi chi 174 when anchored to a suitably derivatized substrate yields arrays of semiconductor nanoparticles matching the shapes of the biopolymer stabilizer. The viability of the methodology was confirmed using high-resolution transmission electron microscopy and selected-area electron diffraction.

Nanostructures↗

PubMed2004

Structural influence of erbium centers on silicon nanocrystal phase transitions.

Two different types of erbium-doped silicon nanocrystals, along with undoped, oxide-capped Si dots, are employed to probe the impact of the impurity center location on phase transition pressure. Using a combination of high pressure optical absorption, micro-Raman, and x-ray diffraction measurements in a diamond anvil cell, it is demonstrated that the magnitude of this phase transition elevation is strongly dictated by the average spatial location of impurity centers introduced into the nanocrystal along with the interfacial quality of the surrounding oxide.

Journal Article↗

PubMed2002

Calcified nanostructured silicon wafer surfaces for biosensing: effects of surface modification on bioactivity.

The growth of known biologically-relevant mineral phases on semiconducting surfaces is one strategy to explicitly induce bioactivity in such materials, either for sensing or drug delivery applications. In this work, we describe the use of a spark ablation process to fabricate deliberate patterns of Ca(10)(PO4)6(OH)2 on crystalline Si (calcified nanoporous silicon). These patterns have been principally characterized by scanning electron microscopy in conjunction with elemental characterization by energy dispersive x-ray analysis. This is followed by a detailed comparison of the effects of fibroblast adhesion and proliferation onto calcified nanoporous Si, calcified nanoporous Si derivatized with alendronate, as well as control samples of an identical surface area containing porous SiO2. Fibroblast adhesion and proliferation assays demonstrate that a higher density of cells grow on the Ca3(PO4)2/porous Si/SiO2 structures relative to the alendronate-modified surfaces and porous Si/SiO2 samples.

Biosensing Techniques↗

PubMedDate not supplied

DNA binding to fluorescent ruthenium species released from calcium phosphate/nanoporous silicon structures.

This work centers on an analysis of calf thymus DNA binding to emissive Ru complexes which diffuse from biocompatible calcium phosphate/nanoporous silicon films. These nanostructures were characterized by scanning electron microscopy, atomic force microscopy, energy dispersive X-ray analysis, and infrared vibrational spectroscopy. In terms of polynucleotide binding, three different systems were analyzed: (1) an aqueous solution of Ru(phen)(3)2+ (a control); (2) surface-adsorbed Ru(phen)(3)2+ onto undoped calcium phosphate/porous Si/Si in aqueous solution; (3) as-prepared and annealed Ru(phen)3(2+)-doped calcium phosphate/porous Si structures in water. For films with fluorescent Ru originally embedded throughout the film, biphasic diffusion character is found; such behavior is attributed to DNA binding to both surface-bound Ru(phen)(3)2+ and species which originate from deeper regions of the film.

Animals↗