Titanium dioxide nanomaterials cause endothelial cell leakiness by disrupting the homophilic interaction of VE-cadherin.

The use of nanomaterials has raised safety concerns, as their small size facilitates accumulation in and interaction with biological tissues. Here we show that exposure of endothelial cells to TiO2 nanomaterials causes endothelial cell leakiness. This effect is caused by the physical interaction between TiO2 nanomaterials and endothelial cells' adherens junction protein VE-cadherin. As a result, VE-cadherin is phosphorylated at intracellular residues (Y658 and Y731), and the interaction between VE-cadherin and p120 as well as ß-catenin is lost. The resulting signalling cascade promotes actin remodelling, as well as internalization and degradation of VE-cadherin. We show that injections of TiO2 nanomaterials cause leakiness of subcutaneous blood vessels in mice and, in a melanoma-lung metastasis mouse model, increase the number of pulmonary metastases. Our findings uncover a novel non-receptor-mediated mechanism by which nanomaterials trigger intracellular signalling cascades via specific interaction with VE-cadherin, resulting in nanomaterial-induced endothelial cell leakiness.

Biomedical applications of hydroxyapatite nanoparticles.

Nanotechnologies have the potential to improve current disease diagnosis due to their ability to circulate in the blood and distribute in the body to image tissues and cells or therapeutical applications to deliver a payload. Among nanoparticles with different materials composition, inorganic nanoparticles composed of calcium phosphate have numerous advantages including ease of synthesis, control of physico-chemical properties, strong interactions with their payload, and biocompatibility. In this review we discuss the different routes of synthesis of calcium phosphate nanoparticles, novel systems, strategies to load agents, biostability and cytotoxicity, biodistribution and pharmacokinetics, bio-imaging and therapeutical applications.

Limb salvage for soft-tissue sarcomas of the foot and ankle.

We evaluated the oncological and functional outcome of 27 patients who had limb salvage for a soft-tissue sarcoma of the foot or ankle between 1992 and 2007, with a mean follow-up of 7.5 years (1.05 to 16.2). There were 12 men and 15 women, with a mean age at presentation of 47 years (12 to 84). Referrals came from other hospitals for 16 patients who had previous biopsy or unplanned excision, and 11 presented de novo. There were 18 tumours located in the foot and nine around the ankle. Synovial sarcoma was the most frequent histological diagnosis. Excision was performed in all cases, with 16 patients requiring plastic surgical reconstruction with 13 free and three local flaps. Adjuvant treatment was undertaken in 20 patients, 18 with radiotherapy and two by chemotherapy. Limb salvage was successful in 26 of the 27 patients. There have been two local recurrences and two mesenchymal metastases. Four patients have died of their sarcoma and two of other causes. Function was evaluated with the Toronto Extremity Salvage Score and a mean overall score of 89.40 (52.1 to 100) was obtained. A questionnaire revealed that all surviving patients are able to wear normal shoes and none require a walking aid. Limb salvage can achieve good oncological and functional results with additional treatment.

Co-synthesis and drug delivery properties of mesoporous hydroxyapatite-silica composites.

In this work, mesoporous hydroxyapatite-silica (HA-silica) composite materials with four different Si:Ca:P ratios were sol-gel derived through self-assembly using triblock copolymer Pluronics P123 as template. The composition and mesoporous structure formed were characterized by X-ray diffraction and electron microscopy. The XRD patterns indicated that the intensity of the HA phase becomes stronger as the Ca/Si ratio of the composite increases. From nitrogen gas analysis at 77 K, type IV isotherm plots for typical mesoporous materials were observed for all of the samples. However, the mesoporous structure of HA-silica tends to becomes less ordered as the Ca/Si ratio increases. Promising consistency between the pore sizes from the Barrett, Joyner and Halenda (BJH) method, Transmission Electron Microscopy (TEM) and Small Angle X-ray diffraction (SAXRD) was also observed. The formation mechanism of mesoporous HA-silica composites was proposed, where the interaction between the crystallization of HA and the surfactant liquid crystal determines the regularity of the meso-structure. In vitro drug loading and release studies showed that drug loading capacity is dependent on the pore volume of the sample, and the mesoporosity of the samples were responsible for the sustained release of drugs. In vitro cell culture of the samples showed promising biocompatibility where osteosarcoma cells were observed to grow favourably on the synthesized composites.

Electronic e-isotretinoin prescription chart: improving physicians' adherence to isotretinoin prescription guidelines.

Oral isotretinoin is a highly effective treatment for refractory nodulocystic acne. However, it can be associated with serious adverse effects such as teratogenicity and hepatitis. Inadequate cumulative dosing may also result in reduced therapeutic efficacy and higher disease relapse. A preliminary audit had previously revealed a poor and inconsistent adherence to local isotretinoin prescribing guidelines by physicians. To achieve greater than 90% adherence to isotretinoin guidelines for all acne patients prescribed systemic isotretinoin at the National Skin Centre, Singapore, key areas and the reasons for non-adherence were identified. A specifically designed 'one-stop' electronic isotretinoin chart was launched within the electronic medical records (EMR) system to address important safety areas; namely, informed patient consent, pregnancy testing, baseline laboratory tests, and automatic calculation of cumulative and target doses of isotretinoin. Physician adherence to prescribing guidelines improved from a baseline of 50-60% to greater than 90% (range 95-100%) for 30 consecutive months post intervention. The e-isotretinoin chart has resulted in significant improvement in physicians' adherence to isotretinoin prescription guidelines and highlights the utility of EMR technology in influencing safe prescribing behaviour among doctors.

In situ SAXRD study of sol-gel induced well-ordered mesoporous bioglasses for drug delivery.

In this work, two systems of mesoporous bioglasses (MBGs) were sol-gel derived using block copolymer pluronic F127 and P123, respectively, as templates. A two-dimensional hexagonal (P6mm) mesoporous structure was obtained for the two systems, with d-spacing in (100) reflection of 8.49 nm for P123-templated MBG (P123-MBG) and 10.26 nm for F127-templated MBG (F127-MBG). The phase transformation behavior for the systems was elucidated using an in situ synchrotron small angle X-ray diffraction approach, with the corresponding mechanisms proposed. It was indicated that both systems go through a complicated phase transformation, from a disordered to a finely ordered hexagonal structure during the self-evaporation process. The surfactants not only acted as templates for the ordered structure, but also enhanced the rigidity of Si-O network, which prevented disruption to the ordered Si-O arrangement by the Ca(2+) and P-O group. In vitro bioactivity study showed similar bioactivity for both the P123-MBG and F127-MBG systems. Drug loading and release studies using a model metoclopramide drug showed that both MBGs presented better loading and release compared to normal bioglass (BG). The significantly higher loading and better sustained release for P123-MBG, compared to F127-MBG, is attributed to its higher pore volume and surface area.

Effects of controlled-released sirolimus from polymer matrices on human coronary artery smooth muscle cells.

Sirolimus-loaded bi-layer polymer matrices were fabricated and the effects of sirolimus release on proliferation and viability of human coronary artery smooth muscle cells (cSMCs) were investigated. Human cSMC recovery after sirolimus treatment and the attachment of human cSMC to sirolimus-eluting films were also studied. It was found that the released sirolimus inhibited growth factor stimulated human cSMC proliferation successfully. However, different drug doses appeared to have the same effect in the extent of inhibition of proliferation in this study. Cell viability was also observed to decrease with the presence of sirolimus and the attachment to sirolimus-eluting films was inhibited. The recovery of human cSMCs was found to be related to the duration of inhibition time by sirolimus. Longer inhibition resulted in a slower recovery, which suggests that sustained release is more effective than rapid release of a higher amount in the inhibition of cSMC proliferation. This observation may be important for the design of a drug-eluting stent.

Differential effects of GH stimulation on fasting and prandial metabolism and plasma IGFs and IGF-binding proteins in lean and obese sheep.

The effect of body condition per se on plasma IGFs and IGF-binding proteins (IGFBPs) and the whole-body metabolic responses to recombinant DNA-derived bovine GH (rbGH) in both the fed and the fasted state were determined in lean and dietary obese sheep (n = 6/group). Sheep at zero-energy balance and equilibrium body weight were injected s.c. for 12 days with 100 micrograms/kg rbGH immediately before their morning feeding. Before GH treatment, fasting plasma concentrations of insulin (17.0 +/- 1.9 vs 7.5 +/- 0.7 microU/ml), IGF-I (345 +/- 25 vs 248 +/- 10 ng/ml), glucose (52.6 +/- 1.1 vs 48.3 +/- 0.7 mg/dl), and free fatty acid (FFA) (355 +/- 45 vs 229 +/- 24 nmol/ml) were greater (P < 0.05) and those of GH (1.1 +/- 0.2 vs 2.6 +/- 0.3 ng/ml) were lower (P < 0.05) in obese than in lean sheep. Fasting concentrations of IGF-II and glucagon were not affected (P > 0.05) by obesity. GH concentrations were increased equivalently by 6-9 ng/ml in lean and obese sheep during GH treatment. GH caused an immediate and a marked fivefold increase in the fasting insulin level in obese sheep but only minimally affected insulin concentration in lean sheep. The increment in fasting glucose during GH treatment was greater (P < 0.05) in obese (8-12 mg/dl) than in lean (2-5 mg/dl) sheep. Frequent measurements in the first 8 h after feeding and injection of excipient (day 0) or the first (day 1) sixth (day 6) and twelfth (day 12) daily injection of GH showed that prandial metabolism in both groups of sheep was affected minimally by GH. However, GH treatment on day 1 (not days 6 or 12) acutely attenuated the feeding-induced suppression of plasma FFA in both groups of sheep and this effect was significantly greater in obese than in lean sheep. Although obese sheep were hyposomatotropic, the basal and GH-induced increases in plasma IGF-I concentrations were greater (P < 0.05) in obese than in lean sheep. Plasma IGF-II was unaffected by obesity and was not increased by GH stimulation. Western ligand blotting showed that IGFBP-3 accounted for approximately 50-60% of the plasma IGF-I binding capacity in sheep respectively both before and during GH treatment. Basal plasma levels of IGFBP-2 were lower (P < 0.05) and those of IGFBP-3 greater (P < 0.05) in obese compared with lean sheep. GH increased the level of IGFBP-3 equally in lean and obese sheep, but suppressed the expression of IGFBP-2 more (P < 0.05) in lean than in obese sheep. We concluded that the diabetogenic-like actions of GH in sheep were exaggerated markedly by obesity, and were expressed more during the fasted than the fed states. The effects of GH stimulation on the endocrine pancreas may be selective for beta-cells and preferentially enhanced by obesity. GH regulation of IGF-I and the IGFBPs differs in lean and obese sheep.

Adrenergic stimulation of regional plasminogen activator release in rabbits.

The purpose of this study was to determine whether different regions of the rabbit vascular system show variations in the rate of plasminogen activator (PA) secretion. To start, we evaluated the time course, dose response and adrenergic specificity of PA release. Infusion of 1 microgram/kg of epinephrine stimulated a 116 +/- 60% (SD) increase in PA activity that peaked 30 to 60 s after epinephrine administration. Infusion of 1 microgram/kg of norepinephrine, isoproterenol and phenylephrine had no effect on PA activity. Pretreatment with phentolamine, an alpha adrenergic antagonist, blocked the release of PA by epinephrine while pretreatment with the beta blocker propranolol had no effect. This suggests that PA release in the rabbit was mediated by some form of alpha receptor. Significant arterio-venous differences in basal PA activity were found across the pulmonary and splanchnic vascular beds but not the lower extremity/pelvic bed. After stimulation with epinephrine, PA activity increased 46% across the splanchnic bed while no change was seen across the lower extremity/pelvic bed. We conclude that several vascular beds contribute to circulating PA activity in the rabbit, and that these beds secrete PA at different rates under both basal and stimulated conditions.

Effect of PAI-1 levels on the molar concentrations of active tissue plasminogen activator (t-PA) and t-PA/PAI-1 complex in plasma.

We determined the in vivo molar concentrations of active tissue plasminogen activator (t-PA), active plasminogen activator inhibitor type 1 (PAI-1), and t-PA/PAI-1 complex. t-PA activity was measured in plasma stabilized by immediate acidification. PAI-1 activity and t-PA/PAI-1 complex antigen were measured in citrated plasma; these measurements were corrected for the loss in PAI-1 activity and increase in complex that occurs in unacidified plasma samples due to the continued reaction between t-PA and PAI-1 after the sample was drawn. To convert t-PA and PAI-1 activity measurements into molar concentrations we determined the specific molar activity of t-PA and PAI-1 in vivo: 4.48 x 10(13) IU/mol. Of 72 subjects studied, 13 had less than 150 pmol/L active PAI-1; in these individuals 33% +/- 21% of their t-PA was active and the molar ratio of active t-PA to active PAI-1 was 0.20 +/- 0.13. In the 11 subjects with greater than 500 pmol/L active PAI-1, 1.5% = 1.1% of the t-PA was active and the molar ratio of active t-PA to active PAI-1 was 0.0043 +/- 0.0036. Overall, the fraction of active t-PA declined exponentially as a function of the active PAI-1 concentration. During the day, the percentage of total t-PA that was active increased from 12% at 8:00 AM to 31% at 8:00 PM, while the molar ratio of active t-PA to active PAI-1 increased from 0.05 to 0.22 from morning to evening (n = 12).

Standardization of methods for measuring plasminogen activator inhibitor activity in human plasma.

We have standardized the measurement of plasminogen activator inhibitor type 1 (PAI-1) activity in plasma. One-chain tissue-type plasminogen activator (t-PA; EC 3.4.21.31; final activity, 5 int. units/mL) was incubated with plasma (final dilutions 1:4 to 1:40) in phosphate buffer (pH 7.4, ionic strength = 0.15) for 15 min at 37 degrees C, followed by acidification and measurement of residual t-PA activity by an amidolytic method. The PAI-1 activity assay was 98% specific for PAI-1 activity in samples from both pregnancy and nonpregnancy, and varied linearly with added plasma volume when the percent inhibition of t-PA was between 8% and 50%. For the standardized method, analytical recovery was 93 +/- 5%, the detection limit was 1.6 arbitrary units per milliliter (1 arb. unit of PAI-1 activity = inhibition of 1 int. unit of t-PA activity), and total imprecision was 10.2 (SD 0.7) arb. units/mL (CV = 7%, n = 20). The average PAI-1 activity in 10 healthy individuals drawn between 0800 and 1000 hours was 23.9 +/- 15.4 arb. units/mL. Compared with the standardized assay, two of three previously described assays underestimated PAI-1 activity in plasma by 77% and 85%, respectively.