2 research outputs found
Synthesis and Characterization of Biomimetic Hydroxyapatite Nanoconstruct Using Chemical Gradient across Lipid Bilayer
In this study, we synthesized biomimetic
hydroxyapatite nanoconstruct
(nanosized hydroxyapatite, NHAp) using a double emulsion technique
combined with a chemical gradient across a lipid bilayer for surface
modification of a titanium (Ti) implant. The synthesized NHAp was
characterized by dynamic light scattering, X-ray diffraction, transmission
electron microscopy, and Fourier transform infrared (FTIR) spectroscopy,
and it was further tested for its biocompatibility and in vitro proliferation
efficacy using normal human osteoblasts (NHOst). The results showed
that the synthesized NHAp had a hydrodynamic diameter of ∼200
nm with high aqueous stability. The chemistry of the NHAp was confirmed
by FTIR spectroscopic analysis. Typical FTIR vibrational bands corresponding
to the phosphate group (PO<sub>4</sub><sup>3–</sup>) present
in hydroxyapatite (HAp) were observed at 670, 960, and 1000 cm<sup>–1</sup>. A broad band at 3500 cm<sup>–1</sup> confirmed
the presence of a structural −OH group in the NHAp. Powder
X-ray crystallographic diffraction further confirmed the formation
of NHAp with characteristic reflections in (002), (211), (130), and
(213) planes at respective 2θ degrees. These reflection planes
are similar to those of typical HAp crystallized toward (002) and
(211) crystallographic planes. The mechanism of the formation of NHAp
was studied using the fluorescence resonance energy transfer (FRET)
technique. The FRET study showed the fluorescent recovery of a donor
fluorophore and the mechanism of the insertion of lipids into nanodroplets
obtained from the first water-in-oil (w/o) emulsion during the formation
of the second oil-in-water (o/w) emulsion. With these confirmations,
we further studied NHOst cell proliferation on a Ti surface. When
NHOst were cultured on the Ti surface coated with the NHAp, a distinct
proliferation pattern and cell–cell communication via cytoplasmic
extension on the substrate surface were observed. In contrast, a bare
Ti surface showed diminished cell size with minimal adherence. This
result indicates that our NHAp covered with a phospholipid bilayer
provides a proper environment essential for cell adhesion, which is
especially important for bone implants, and the inclusion of NHAp
on the Ti substrate would be an effective support for long-term sustainability
of implants
Data_Sheet_1_Fabrication of Circular Obelisk-Type Multilayer Microneedles Using Micro-Milling and Spray Deposition.docx
<p>In this study we present the fabrication of multilayer microneedles with circular obelisk and beveled-circular obelisk geometries, which have potential applications in implantable drug delivery devices. Micro-milling was adopted as an environmental-friendly and cost-effective way to fabricate primary metal microneedle masters. Polylactic acid (PLA) microneedles with sharp tips were then obtained by micromolding followed by oxygen plasma etching and used for preparing polydimethylsiloxane (PDMS) microneedle molds. A spray deposition process was employed for microneedle fabrication to facilitate the formation of multilayer microneedles while helping in maintenance of drug stability. Multilayer microneedles were successfully formed by sequential spraying of poly(lactic-co-glycolic acid) (PLGA) and polyvinylpyrrolidone (PVP) solutions into the mold. The fabricated PLGA-PVP multilayer microneedles penetrated the pig cadaver skin without breakage and released dyes in the skin at different rates, which reveals the potential for implantable microneedles enabling controlled release. Mechanical testing demonstrated that the obelisk-shaped microneedles were mechanically stronger than a pyramid-shaped microneedle and suggested that strong adhesion between PLGA and PVP layers was achieved as well. Structural stability and functionality of a model drug, horseradish peroxidase (HRP), upon spray deposition was examined using circular dichroism (CD) spectroscopy and enzyme activity assay. HRP retained its secondary structure and activity in PVP, whereas HRP in PLGA showed structural changes and reduced activity. Combination of micro-milling and spray deposition would be an attractive way of fabricating drug-containing polymer microneedles with various geometries while reducing prototyping time and process-induced drug instability.</p