Previous studies have demonstrated the potential of fibrin as a cell carrier for cardiovascular tissue engineering applications. Unfortunately, fibrin exhibits poor mechanical properties. One method of addressing this issue is to incorporate a textile in fibrin to provide structural support. However, it is first necessary to develop a deeper understanding of the effect of the textile on cell response. In this study, the cytotoxicity of a polylactic acid (PLA) warp-knit textile was assessed with human coronary artery smooth muscle cells (HCASMC). Subsequently, quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) was employed to examine the gene expression of HCASMC embedded in fibrin with and without the textile. Five genes were examined over a 3-week period: smooth muscle α-actin (SMαΑ), myosin heavy chain 11 smooth muscle (SM1/SM2), calponin, myosin heavy chain 10 non-muscle (SMemb) and collagen. Additionally, a microarray analysis was performed to examine a wider range of genes. The knitting process did not adversely affect the cell response; there was no dramatic change in cell number or metabolic rate compared to the negative control. After 3 weeks, there was no significant difference in gene expression, except for a slight decrease of 10% in SMemb in the fibrin with textile. After 3 weeks, there were no obvious cytotoxic effects observed as a result of the knitting process and the gene expression profile did not appear to be altered in the presence of the mesh in the fibrin gel.

In vivo, endothelial cells (EC) are constantly exposed to the haemodynamic forces (HF) of pressure, wall shear stress and hoop stress. The main aim of this study was to design, create and validate a novel perfusion bioreactor capable of delivering shear stress and intravascular pressure to EC in vitro and to characterise their morphology, orientation and gene expression. Here we report the creation and validation of such a simulator and the dual application of pressure (120/60 mmHg) and low shear stress (5 dyn/cm(2)) to a monolayer of EC established on a non-compliant silicone tube. Under these conditions, EC elongated and realigned obliquely to the direction of applied shear stress in a time-dependent manner. Furthermore, randomly distributed F-actin microfilaments reorganised into long, dense stress fibres crossing the cells in a direction perpendicular to that of flow. Finally, combinatorial biomechanical conditioning of EC induced the expression of the inflammatory-associated E-selectin gene.

Phthalocyanine derivatives are currently under investigation for use in photodynamic therapy, which is a promising cancer treatment. These materials, which display preferential uptake in cancerous cells, also exhibit high fluorescence yields and can be used for tumour detection. Problems with steady-state fluorescence techniques such as excitation scatter and background autofluorescence can be eliminated by using time-resolved imaging techniques without the need for filters. A tissue phantom was assembled to test a constructed time-gated imaging system by drilling 36 wells of varying diameter and depth (10 mm to 1 mm) into a block of polymethyl methacrylate (PMMA). The system was used to record images of chloroaluminium phthalocyanine tetrasulfonate (AlPcTS) at differing concentrations in neat aqueous solvent and cell suspensions within the wells. A mixture of Intralipid (to mimic tissue scatter) and Evan's blue (to mimic tissue absorption) of depths ranging from 1 mm to 10 mm was placed on top of the PMMA block. The ensuing images were analysed using signal-to-noise ratios and contrast-detail curves. The results indicate that the time-gated imaging system can prevent background excitation scatter from distorting the fluorescence signal from a longer-lived photosensitizer without the need for filters.

The use of fluorescence for cancer detection is currently under investigation. Presently, steady-state fluorescence detection methods are in use, but have limitations due to poor contrast between the fluorescence of the tumor and background autofluorescence. Improved contrast can be obtained with time-resolved techniques because of the differing lifetimes between autofluorescence and exogenous photosensitizers that selectively accumulate within tumor tissue. An imaging system is constructed using a fast-gated (200-ps) charge-coupled device (CCD) camera and a pulsed 635-nm laser diode. To characterize the ability of the system to transfer object contrast to an image, the modulation transfer function (MTF) of the system is acquired by employing an extended knife-edge technique. A knife-edge target is assembled by drilling a rectangular well into a block of polymethyl methacrylate (PMMA). The imaging system records images of the photosensitizer, chloroaluminum phthalocyanine tetrasulfonate (AlPcTS), within the well. AlPcTS was chosen to test the system because of its strong absorption of 635-nm, high fluorescence yield, and relatively long fluorescence lifetime (approximately 7.5 ns). The results show that the system is capable of resolving 10(-4) M AlPcTS fluorescence as small as 1 mm. The findings of this study contribute to the development of a time-gated imaging system using fluorescence lifetimes.

Porphycenes are currently under investigation for use in Photodynamic therapy, which is a promising treatment for cancer. These materials, which display preferential uptake in cancerous cells, also exhibit high fluorescence yields, and can be used for tumour detection. Problems with steady-state fluorescence techniques such as background autofluorescence can be eliminated by the use of time-reolved techniques. Improved contrast can be obtained with time-resolved techniques because of the differing fluorescence lifetimes between autofluorescence and longer-living exogenous photosensitisers. An imaging system was constructed using a fast (200 ps) gated CCD camera and a pulsed 635 nm laser diode. A tissue phantom composed of polymethyl methacrylate (PMMA) with thirty-six wells of varying diameter and depth (10 mm to 1 mm) was assembled to test the system. The system was used to record images of a porphycene derivative within the wells at differing concentrations in an organic solvent. A tissue imitator was placed on top of the PMMA block at varying thickness. 10(-4) M zinc phthalocyanine tetrasulfonate was also placed on top of the block to mimic autofluorescence. The results indicate that the time-gated imaging system can prevent background excitation scatter and fluorescence from a shorter-lived fluorophore from distorting the fluorescence signal from a longer-lived photosensitiser.

Phthalocyanine derivatives. are currently under investigation for use in Photodynamic Therapy, which is a promising treatment, for cancer. These materials, which display preferential uptake in cancerous cells, also exhibit high fluorescence yields; and can be used for tumour detection. Problems with steady-state fluorescence techniques such as background autofluorescence can be eliminated by the use of time-resolved techniques. Improved contrast can be obtained with time-resolved techniques because of the differing lifetimes between endogenous and exogenous photosensitisers. An imaging system was constructed using a fast (200 psec) gated CCD camera and a pulsed 635 rim laser diode. A tissue phantom was assembled to test the system by drilling thirty-six wells of varying diameter and depth (10 mm to 1 mm) into a block of polymethyl methacrylate (PMMA). The system was used to record images of chloroaluminum phthalocyanine tetrasulfonate within the-wells at differing concentrations in phosphate buffer. A mixture of 1) Intralipid to mimic tissue scatter, 2) Evans blue to mimic tissue absorption, and 3) zinc phthalocyanine tetrasulfonate to mimic-healthy tissue:autofluorescence of varying depth was placed on top of the PMMA block. These results contribute to the precision of a time-gated imaging system to image living organisms using fluorescence lifetimes.

Various chemicals used for photodynamic therapy, a promising treatment for cancer, exhibit high fluorescence yields which can be used for tumour detection. For a chosen few such compounds fluorescence lifetimes, absorption, and steady state fluorescence spectra were measured at different concentrations (ranging from 10 -5 M to 10 -8 M) in a variety of solvents The lifetimes were repeated at three different concentrations (ranging from 10 -5 M to 10 -6 M) in suspensions of 3T3 fibroblast cells.