No abstract

Next-generation bone implants will be functionalized with drugs for stimulating bone growth. Modelling of drug release by such functionalized biomaterials and drug dispersion into bone can be used as predicting tool for biomaterials testing in future. Therefore, the determination of experimental parameters to describe and simulate drug release in bone is essential. Here, we focus on Sr 2+ transport and quantification in cortical rat bone. Sr 2+ dose-dependently stimulates bone-building osteoblasts and inhibits bone-resorbing osteoclasts. It should be preferentially applied in the case of bone fracture in the context of osteoporotic bone status. Transport properties of cortical rat bone were investigated by dipping experiments of bone sections in aqueous Sr 2+ solution followed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling. Data evaluation was carried out by fitting a suitable mathematical diffusion equation to the experimental data. An average diffusion coefficient of D = (1.68 ± 0.57) · 10 −13 cm 2 s −1 for healthy cortical bone was obtained. This value differed only slightly from the value of D = (4.30 ± 1.43) · 10 −13 cm 2 s −1 for osteoporotic cortical bone. Transmission electron microscopy investigations revealed a comparable nano- and ultrastructure for both types of bone status. Additionally, Sr 2+ -enriched mineralized collagen standards were prepared for ToF-SIMS quantification of Sr 2+ content. The obtained calibration curve was used for Sr 2+ quantification in cortical and trabecular bone in real bone sections. The results allow important insights regarding the Sr 2+ transport properties in healthy and osteoporotic bone and can ultimately be used to perform a simulation of drug release and mobility in bone.

No abstract

CHEMISTRY however, are the results obtained with ether-soluble lac. The values reported in the literature for this portion of lac are generally between 90 and 110, compared with the low value of 70 obtained by the present method. Possibly the ether-soluble portion of lac contains ester linkages highly susceptible to alkali; a structure involving a lactone linkage has been suggested by Bhowmik and Sen (7). The saponification value of the ether-soluble lac is about the same as that mentioned in the literature.

In this work, we present systematic electron spin resonance ͑ESR͒ experiments on SiGe quantum-dot structures. A series of samples with different sizes of quantum dots is prepared by varying growth temperature and spacing between quantum-dot layers. At a frequency of about 9.5 GHz, two ESR signals with g factors around 1.9992 and 1.9994 are observed with magnetic field in growth direction. The signals shift and broaden with magnetic field in the in-plane direction. The estimated dephasing time T 2 ‫ء‬ amounts up to 500 ns. The saturation behavior yields relaxation time T 1 of about 10 s. The relative intensity between the two peaks can be changed with illumination with subband-gap light. The two peaks are interpreted as s-and p-like states of electrons confined in the strained Si around the SiGe nanostructures.