In this paper we describe the preparation of fluorescent mesoporous silica nanoparticles (MSNs) for traceable drug delivery systems. The nanoparticles were prepared following a sol–gel procedure, incorporating a modified perylenediimide dye in the silica structure. Transmission electron microscopy and scanning electron microscopy show that the nanoparticles are monodispersed, with a spheroid shape and a raspberry-type surface morphology. The hybrid MSNs are robust, maintaining the mesoporous structure after template removal, with a pore diameter above 2 nm. A polymer shell was synthesized from the external surface of the hybrid nanoparticles by atom transfer radical polymerization, showing temperature-switchable collapsed/expanded conformation control. The fluorescent properties of the perylenediimide dye incorporated in the MSN pore walls are intact, and internalization in HEK293 cells shows that the nanoparticles are efficiently dispersed in the cytosol. These results show that the mesoporous fluorescent hybrid nanoparticles are an excellent platform for development of a traceable drug delivery system.

The microstructure of carbon–carbon composites obtained by chemical vapor infiltration of a carbon fiber felt was comparatively studied by reflection light microscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), and laser scanning confocal microscopy (LSCM). Ar+ ion etching was used to reveal and distinguish structural units of the pyrolytic carbon matrix. Mechanically polished samples, polished and subsequently ion etched samples, and fractured samples were compared. The values of surface roughness and surface height after polishing or after polishing and subsequent etching determined by AFM and LSCM correlate well with the degree of texture of the matrix layers obtained by polarized light microscopy and selected area electron diffraction. The carbon matrix is composed of structural units or “cells,” which contain a carbon fiber and a sequence of several differently textured layers around each fiber. Within high-textured layers columnar grains are well recognizable using polarized reflection light microscopy and confocal microscopy. The size of depressions within high-textured carbon layers found by AFM after ion etching correlates well with the size of differently tilted domains detected by both TEM and SEM.

Microdamage in bone contributes to the loss of bone quality in osteoporosis and is thought to play a major role in both fragility and stress fractures (Schaffler et al. 1995). In this study, in vivo microcracks in human ribs were bulk-stained in basic fuchsin and viewed in longitudinal section and in 3 dimensions using 2 different computer-based methods of reconstruction: (1) serial sectioning of methylmethacrylate embedded sections using a sledge macrotome and identification of microcracks using UV epifluorescence followed by computerised reconstruction of microcracks using software and (2) laser scanning confocal microscopy of thick sections followed by reconstruction of microcracks into a 3-D image. The size and shape of microcracks were found to be similar using both techniques. Both techniques of reconstruction showed microcracks to be approximately elliptical in shape. From the serial sectioning reconstructions (n = 9), microcracks were found to have a mean length of 404±145 μm (mean±S.D.) (in the longitudinal direction) and mean width of 97±38 μm (in the transverse direction). Using epifluorescence microscopy, 92 microcracks were identified; mean microcrack length was 349±100 μm in the longitudinal direction. This was consistent with other results (Burr & Martin, 1993) and with the theoretical prediction of an elliptical crack shape with aspect ratio (longitudinal[ratio ]transverse) of 5[ratio ]1 deduced from analysis of random 2-D sections (Taylor & Lee, 1998). The results obtained provide new data on the nature of microcracks in bone and the method has the potential to become a useful tool in the calculation of stress intensity values which indicate the probability of an individual microcrack propagating to cause a stress or fragility fracture.

Fibre optic confocal imaging (FOCI) enabled subsurface fluorescence microscopy of the skin of hairless mice in vivo. Application of acridine orange enabled imaging of the layers of the epidermis. The corneocytes of the stratum corneum, the keratinocytes in the basal layers and redundant hair follicles were visualised at depths greater than 100 μm. Cellular and nuclear membranes of keratinocytes of the skin were visualised by the use of acridine orange and DIOC5(3). Imaging of the skin after injection of FITC-dextran revealed an extensive network of blood vessels with a size range up to 20 μm. Blood cells could be seen moving through dermal vessels and the blood circulation through the dermal vascular bed was video-taped. The fluorescent dye 4-di-2-ASP showed the presence of nerves fibres around the hair follicles and subsurface blood vessels. Comparison was made between images obtained in vivo using FOCI and in vitro scanning electron microscopy and conventional histology. FOCI offers the potential to study dynamic events in vivo, such as blood flow, skin growth, nerve regeneration and many pathological processes, in ways which have not previously been possible.