Nanoengineered surfaces enhance drug loading and adhesion.

To circumvent the barriers encountered by macromolecules at the gastrointestinal mucosa, sufficient therapeutic macromolecules must be delivered in close proximity to cells.(1) Previously, we have shown that silicon nanowires penetrate the mucous layer and adhere directly to cells under high shear.(2) In this work, we characterize potential reservoirs and load macromolecules into interstitial space between nanowires. We show significant increases in loading capacity due to nanowires while retaining adhesion of loaded particles under high shear.

Analysis of various organic and organometallic compounds using nanostructure-assisted laser desorption/ionization time-of-flight mass spectrometry (NALDI-TOFMS).

Nanostructure-assisted laser desorption/ionization time-of-flight mass spectrometry (NALDI-TOFMS) has been developed recently as a matrix-free/surface-assisted alternative to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The NALDI surface of silicon nanowires is already very effective for the analysis of small to medium sized, polar organic molecules in positive ion mode. The current study examined this technology for the analysis of several nonpolar organic, organometallic, and ionic compounds in positive ion mode, as well as a fluorinated compound and various acids in negative ion mode. NALDI data are compared and contrasted with MALDI data for the same compounds, and the higher sensitivity of NALDI is highlighted by the successful characterization of two porphyrins for a sample amount of 10 amol per spot.

Effect of nanofiber-coated surfaces on the proliferation and differentiation of osteoprogenitors in vitro.

The osteoconductive property of titanium (Ti) surfaces is important in orthopedic and dental implant devices. Surface modifications of Ti have been proposed to further improve osseointegration. In this study, three different materials, silicon (Si), silicon oxide (SiO(2)), and titanium oxide (TiO(2)), were used to construct nanofibers for surface coating of Ti alloy Ti-6Al-4 V (Ti alloy). MC3T3-E1 osteoprogenitor cells were seeded on nanofiber-coated discs and cultured for 42 days. DNA, alkaline phosphatase, osteocalcin, and mineralization nodules were measured using PicoGreen, enzyme-linked immunosorbent assay, and calcein blue staining to detect the attachment, proliferation, differentiation, and mineralization of MC3T3-E1 cells, respectively. The results demonstrated that the initial cell attachments on nanofiber-coated discs were significantly lower, although cell proliferation on Si and SiO(2) nanofiber-coated discs was better than on Ti alloy surfaces. TiO(2) nanofibers facilitated a higher cellular differentiation capacity than Ti alloy and tissue culture-treated polystyrene surfaces. Thus, surface modification using nanofibers of various materials can alter the attachment, proliferation, and differentiation of osteoprogenitor cells in vitro.

Nanostructured surfaces for bone biotemplating applications.

A major goal of orthopedic biomaterials research is to design better surface chemistries and configurations to control behavior of bone cells such as osteoblasts. Nanostructured architecture significantly affects the response of several cell lines. In this work, nanostructured surfaces were prepared by vapor liquid solid growth of silicon nanowires from size-controlled gold colloid catalysts deposited on fused silica substrates. The lengths and surface densities of the nanowires were varied to assess the effect of these parameters on bone cell response. Osteoblasts were seeded on nanowire surfaces to investigate both short-term adhesion and proliferation and long-term functionality and matrix production. Cell adhesion and proliferation were characterized using a standard 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide assay and cell counting for up to 4 days of culture. The total protein content, alkaline phosphatase activity, and matrix production were quantified using standard colorimetric assays for up to 4 weeks of culture. Matrix production was also characterized by measuring surface concentrations of calcium and phosphorus using X-ray photoelectron spectroscopy. Further, scanning electron microscopy was used to investigate osteoblast morphology on nanostructured surfaces. Over the 4-week study, the nanostructured surfaces demonstrated improved osteoblast adhesion and proliferation and increased alkaline phosphatase activity and matrix production compared to non-nanostructured control surfaces.