We present a generalized table of extinction coefficient data for silver nanoparticles from 8 to 100 nm. This table allows for easy and quick estimation of the concentration and size of modified and mono-dispersed silver nanoparticles from their optical spectra. We obtained data by determining the silver content of citrate-stabilised silver nanoparticles using sodium cyanide to dissolve the nanoparticles, and measuring solution conductivity with a pH meter and a cyanide-ion selective electrode. The quantification of the silver ion concentration enabled the calculation of extinction coefficients. Experimentally calculated extinction coefficients, in the current work, are in good agreement with collated literature values measured by different authors with non-standardized methodology and each for a limited range of particle size. They are also in good agreement with our theoretical calculations using Mie theory. Thus, we provide a highly standardized and comprehensive tabulated reference data-set.

Adipose tissue equivalents have not been addressed as yet despite the clinical need in congenital deformities, posttraumatic repair, cancer rehabilitation, and other soft tissue defects. Preadipocytes were successfully harvested from rat epididymal fat pads of Sprague-Dawley and Lewis rats and expanded ex vivo. In vitro cultures demonstrated full differentiation of preadipocytes into mature adipocytes with normal lipogenic activity. The onset of differentiation was well-controlled by regulating preadipocyte confluency. Poly(lactic-co-glycolic) acid (PLGA) polymer disks with 90% porosity, 2.5 mm thick, 12 mm diameter, pore size range of 135-633 microm were fabricated and seeded with preadipocytes at 10(5) cells/mL. Disks in vitro demonstrated fully differentiated mature adipocytes within the pores of the disks. Short-term in vivo experiments were conducted by implanting preseeded disks subcutaneously on the flanks of rats for 2 and 5 weeks. Histologic staining of harvested disks with osmium tetroxide (OsO4) revealed the formation of adipose tissue throughout the disks. Fluorescence labeling of preadipocytes confirmed that formed adipose tissue originated from seeded preadipocytes rather than from possible infiltrating perivascular tissue. This study demonstrates the potential of using primary preadipocytes as a cell source in cell-seeded polymer scaffolds for tissue engineering applications.

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Dual polarization interferometry (DPI) is used for a detailed study of antibody immobilization with and without orientation control, using prostate specific antigen (PSA) and its antibody as model. Thiol modified DPI chips were activated by a heterobifunctional cross-linker (sulfo-GMBS). PSA antibody was either directly immobilized via covalent binding or coupled via the Fc-fragment to protein G covalently attached to the activated chip. The direct covalent binding leads to a random antibody orientation and the coupling through protein G leads to an end-on orientation. Ethanolamine (ETH) was used to block remaining active sites following the direct antibody immobilization and protein G immobilization. A homobifunctional cross-linker (BS3) was used to stabilize the antibody layer coupled on protein G. DPI provides a real-time measurement of the stepwise molecular binding processes and gives detailed geometrical and structural values of each layer, i.e., thickness, mass, and density. These values evidence the end-on orientation of closely packed antibody on protein G layer and reveal structural effects of ETH blocking/deactivation and BS3 stabilization. With the end-on immobilized antibody, PSA at 10 pg/mL can be detected by DPI through a sandwich complex that satisfies the clinical requirement (assuming <30 pg/mL as clinically safe). However, the randomly immobilized antibody failed to detect PSA at 1 ng/mL. In a parallel study using surface plasmon resonance (SPR) spectroscopy, random and end-on antibody immobilization on streptavidin-modified gold surface was evaluated to further validate the importance of antibody orientation control. With the closely packed antibody layer on protein G surface, SPR can also detect PSA at 10 pg/mL.