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This study focuses on the use of bio-nanocomposite microspheres, consisting of carbonated hydroxyapatite (CHAp) nanospheres within a poly(L: -lactide) (PLLA) matrix, to produce tissue engineering (TE) scaffolds using a modified selective laser sintering (SLS) machine. PLLA microspheres and PLLA/CHAp nanocomposite microspheres were prepared by emulsion techniques. The resultant microspheres had a size range of 5-30 microm, suitable for the SLS process. Microstructural analyses revealed that the CHAp nanospheres were embedded throughout the PLLA microsphere, forming a nanocomposite structure. A custom-made miniature sintering platform was installed in a commercial Sinterstation((R)) 2000 SLS machine. This platform allowed the use of small quantities of biomaterials for TE scaffold production. The effects of laser power; scan spacing and part bed temperature were investigated and optimized. Finally, porous scaffolds were successfully fabricated from the PLLA microspheres and PLLA/CHAp nanocomposite microspheres. In particular, the PLLA/CHAp nanocomposite microspheres appeared to be promising for porous bone TE scaffold production using the SLS technique.

This study investigated the nanoemulsion technique as a means to synthesize carbonated hydroxyapatite (CHAp) nanospheres which could be used to produce composite tissue engineering scaffolds. CHAp nanospheres were successfully synthesized by mixing an acetone solution of Ca(NO(3))(2).4H(2)O with an aqueous solution of (NH(4))(2)HPO(4) and NH(4)HCO(3). Four reaction temperatures, namely, 4, 25, 37 and 55 degrees C, were investigated and no surfactant was added in all nanoemulsion processes. Wet slurries of CHAp from the nanoemulsions were freeze-dried to obtain dry powders. X-ray diffraction (XRD) results showed that the as-synthesized CHAp nanoparticles were mainly in an amorphous state. After calcination at 900 degrees C, the apatite became well crystallized. Fourier transform infrared (FTIR) spectroscopy showed that the CHAp was B-type substitution. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the CHAp particles were spherical in shape and that their sizes were in the nanometer range. The successful synthesis of CHAp nanospheres is a critical step forward in our efforts to fabricate bone tissue engineering scaffolds using the selective laser sintering technology.

In this study, transparent poly(vinyl alcohol) (PVA) and PVA/halloysite nanotubes (HNTs) bionanocomposite films were prepared by solution casting and glutaraldehyde (GA) crosslinking. The surface topography and chemistry of the films were characterized by atomic force microscopy (AFM) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, respectively. Blending with HNTs induced changes in nanotopography and surface chemistry of PVA films. The mechanical properties of PVA were enhanced by the incorporated HNTs. The stain-induced crystallization was confirmed by DSC after tensile test. MC3T3-E1 osteoblast-like and NIH 3T3 fibroblast cells were cultured on neat PVA and PVA/HNTs films to evaluate the effects of surface nanotopography and composition on cell behavior. The observations indicated that MC3T3-E1 cell behavior strongly responded to surface nanotopography. On nanotube-dominant surface, cells exhibited a significantly higher level of adhesion than on neat PVA film, whereas neat PVA showed higher degree of osteoblast proliferation compared with PVA/HNTs. In vitro fibroblasts response demonstrated that both neat PVA and PVA/HNTs nanocomposite films were biocompatible and PVA/HNTs films favored to fibroblasts attach and growth below 7.5 wt % of HNTs incorporated. In summary, these results provided insights into understanding of PVA and PVA/HNTs bionanocomposite films in potential applications in bone tissue engineering and drug delivery systems.

Microspheres consisting of carbonated hydroxyapatite (CHAp) nanoparticles and poly(L-lactide) (PLLA) have been fabricated for use in the construction of osetoconductive bone tissue engineering scaffolds by selective laser sintering (SLS). In SLS, PLLA polymer melts and crystallizes. It is therefore necessary to study the crystallization kinetics of PLLA/CHAp nanocomposites. The effects of 10 wt% CHAp nanoparticles on the isothermal and nonisothermal crystallization behavior of PLLA matrix were studied, using neat PLLA for comparisons. The Avrami equation was successfully applied for the analysis of isothermal crystallization kinetics. Using the LauritzenHoffman theory, the transition temperature from crystallization Regime II to Regime III was found to be around 120 C for both neat PLLA and PLLA/CHAp nanocomposite. The combined Avrami-Ozawa equation was used to analyze the nonisothermal crystallization process, and it was found that the Ozawa exponent was equal to the Avrami exponent for neat PLLA and PLLA/CHAp nanocomposite, respectively. The effective activation energy as a function of the relative crystallinity and temperature for neat PLLA and PLLA/CHAp nanocomposite under the nonisothermal crystallization condition was obtained by using the Friedman differential isoconversion method. The Lauritzen-Hoffman parameters were also determined from the nonisothermal crystallization data by using the Vyazovkin-Sbirrazzuoli equation. CHAp nanoparticles in the composite acted as an efficient nucleating agent, enhancing the nucleation rate but at the same time reducing the spherulite growth rate. This investigation has provided significant insights into the crystallization behavior of PLLA/CHAp nanocomposites, and the results obtained are very useful for making good quality PLLA/CHAp scaffolds through SLS.

We present a focusing subwavelength grating (SWG) for efficient coupling of mid-infrared (mid-IR) light into suspended membrane Ge photonic integrated circuits (PICs) that enable mid-IR applications in the entire fingerprint region. By virtue of their wide spectral transparency window and air-cladding device configuration, the suspended membrane Ge PICs are expected to be effective for mid-IR applications over the spectral region covering from 2 to 15 μm. Specifically, we demonstrate the maximum coupling efficiency of -11  dB with a 1-dB bandwidth of ∼58  nm at the SWG's center wavelength of 2.37 μm. Our focusing SWG is expected to advance the development of on-chip long-wavelength mid-IR applications such as biochemical sensing, thermal imaging, and nonlinear optics in the fingerprint region.

This paper presents a 2300 nm wavelength photodetector which comprises a spin‐deposited colloidal HgTe quantum dot (QD) film on a metal‐insulator‐metal (MIM) plasmonic waveguide. This photodetector is an integrated device based on the complementary metal‐oxide‐semiconductor compatible silicon‐on‐insulator platform. The device employs input and output silicon waveguide grating couplers, and HgTe QDs are used as the infrared photosensing material. Infrared light is coupled to the strongly confined MIM waveguide mode, which shrinks the device footprint and improves the light detection efficiency simultaneously. A room temperature responsivity of 23 mA W−1 and a noise‐equivalent power of 8.7 × 10−11 W Hz−1/2 at 2300 nm wavelength are achieved by the photodetector at 2.14 W mm−2 (measured at the input to the plasmonic waveguide) with a device footprint of 15 µm × 0.35 µm. The light intensity–dependent photocurrent, the current noise spectral density, and the 3 dB operation bandwidth are all characterized. The charge transfer properties of the organic HgTe QD films are further analyzed based on field effect transistor measurements.

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