Tunable chemical release from polyester thin film by photocatalytic zinc oxide and doped LiYF4 upconverting nanoparticles.

Once manufactured or implanted, polyester release kinetics tend to be fixed with little modulation possible for optimal local chemical concentrations. Here, a typical implantable polyester was fabricated into thin films (∼50 µm thick) with additives of photocatalytic ZnO nanoparticles, lanthanide-doped LiYF4 nanoparticle upconverting nanoparticles, or a combination thereof and irradiated with either 6 mW ultraviolet (365 nm) light emitting diodes or 50 mW near-infrared (980 nm) laser diodes to induce polymer photooxidation. Irradiated polyester films with the aforementioned photoadditives had enhanced release kinetics up to 30 times more than nonirradiated, neat films with extended release times of 28 days. Near-infrared, ZnO-mediated photocatalysis had the highest light on/light off ratio release kinetics of 15.4, while doped LiYF4 upconversion nanoparticles paired with ZnO nanoparticles had the highest linear R(2) correlation of 0.98 with respect to duty cycle and release kinetics. Future applications of the technology will aim toward modulation of previously developed polymeric reagents/drugs for real-time, feedback-optimized release.

Tissue engineering scaffold for sequential release of vancomycin and rhBMP2 to treat bone infections.

The ability of silica calcium phosphate nanocomposite (SCPC75) for the controlled sequential delivery of vancomycin (Vanc) and rhBMP2 was evaluated. Fourier transform infrared spectroscopy analyses of the SCPC75 showed an increase in the bond energy of the PO4 (-3) due to the interactions with negatively charged moieties of Vanc. Furthermore, a decrease in the bond energy of the Si-O-Si functional groups was observed after rhBMP2 adsorption. In conjunction with the differences in bond site and bond energy at the ceramic/drug interface, significant differences in drug release kinetics and bioceramic dissolution rate were found. UV-vis spectrometry showed a burst release of Vanc in the first 8 h followed by a sustained release stage for up to 28 days. ELISA showed first-order release kinetics of rhBMP2 without burst release. The rhBMP2 release from SCPC75 was associated with a significantly lower rate of Ca and a higher rate of Si dissolutions when compared with Vanc release over identical time periods. Differences in the release kinetic profiles of Vanc and rhBMP2 from the SCPC75-Vanc/SCPC75-rhBMP2 scaffolds at 70/30, 50/50, or 20/80 ratios allowed for sequential drug release profiles that could be exploited to customize doses and release duration of each drug. The released rhBMP2 significantly upregulated MC3T3-E1 expression of collagen type I, osteopontin, and osteocalcin mRNA by 12.6-, 3.3-, and 2.4-fold, respectively. The released Vanc demonstrated bactericidal effects on Staphylococcus aureus in vitro. These results suggest the potential of SCPC75-Vanc-rhBMP2 scaffolds in the treatment of damaged and/or infected bone.

Development of a probucol-releasing antithrombogenic drug eluting stent.

The success of drug eluting stents (DESs) has been challenged by the manifestation of late stent thrombosis after DES implantation. The incomplete regeneration of the endothelial layer poststenting triggers adverse signaling processes precipitating in thrombosis. Various approaches have been attempted to prevent thrombosis, including the delivery of biological agents, such as estradiol, that promote endothelialization, and the use of natural polymers as coating materials. The underlying challenge has been the inability to release the biological agent in synchronization with the temporal sequence of vascular wound healing in vivo. The natural healing process of the endothelium after an injury starts after a week and may take up to a month in humans. This article presents a novel DES formulation using a hemocompatible polyurethane (PU) matrix to sustain the release of probucol (PB), an endothelial agonist, by exploiting the greater difference in the solubility parameters of PB and PU. This results in the formation of crystalline PB aggregates retarding drug release from PU. The physicochemical properties of PB in PU were confirmed using differential scanning calorimetry and X-ray diffraction. Drug-polymer compatibility was examined using infrared spectral analysis. Also, in vitro studies using primary human aortic endothelial cells resulted in the selection of 5% w/w PB as the optimal dose, to be further tested in vitro and in vivo. This work develops and tests a promising new DES formulation to enable faster endothelial cell proliferation poststenting, potentially minimizing the incidence and severity of thrombotic events after DES implantation.

Evaluation of a bioresorbable drug delivery system for the treatment of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) represents a major global health burden. Typically HCC responds poorly to chemotherapy, and such approaches to treat HCC are commonly associated with severe hepatic and/or systemic toxicity. The aim of this study was to evaluate a porous resorbable silica-calcium phosphate nanocomposite (SCPC) as a controlled release vehicle for cisplatin. Particles of two different formulations--SCPC50 and SCPC75, containing 19.49 and 32.9 mol % silica, respectively--were loaded with cisplatin by immersion treatment and pressed into discs. In vitro release kinetics studies of cisplatin from SCPC50 and SCPC75 demonstrated an initial burst release of 0.39 ± 0.04 mg (of the 1.49 mg total loaded) and 0.87 ± 0.07 mg (of the 2.34 mg total loaded), respectively. Over the following 44-day period. SCPC75-cisplatin hybrid produced a significantly higher sustained cisplatin release than that released from SCPC50. Cisplatin release correlated well with the surface area, and silica dissolution kinetics of the SCPC carrier. Treatment of rat HCC cells (H4IIE) with cisplatin released from SCPC-cisplatin hybrids induced apoptotic cell death in H4IIE cells in vitro. Results of this study suggest that SCPC composites may be of potential use for the treatment of HCC in vivo.

A ceramic-based anticancer drug delivery system to treat breast cancer.

Drug delivery systems offer the advantage of sustained targeted release with minimal side effect. In the present study, the therapeutic efficacy of a porous silica-calcium phosphate nanocomposite (SCPC) as a new delivery system for 5-Fluorouracil (5-FU) was evaluated in vitro and in vivo. In vitro studies showed that two formulations; SCPC50/5-FU and SCPC75/5-FU hybrids were very cytotoxic for 4T1 mammary tumor cells. In contrast, control SCPCs without drug did not show any measurable toxic effect. Release kinetics studies showed that SCPC75/5-FU hybrid provided a burst release of 5-FU in the first 24 h followed by a sustained release of a therapeutic dose (30.7 microg/day) of the drug for up to 32 days. Moreover, subcutaneous implantation of SCPC75/5-FU hybrid disk in an immunocompetent murine model of breast cancer stopped 4T1 tumor growth. Blood analyses showed comparable concentrations of Ca, P and Si in animals implanted with or without SCPC75 disks. These results strongly suggest that SCPC/5-FU hybrids can provide an effective treatment for solid tumors with minimal side effects.

A study of drug release from homogeneous PLGA microstructures.

The hydrogel template method was used to fabricate homogeneous drug-PLGA microparticles. Four drugs (felodipine, risperidone, progesterone, and paclitaxel) were loaded into the PLGA particles with the homogeneous size of 10microm, 20microm, and 50microm. The drug loading into the PLGA microparticles was 50% and higher. The felodipine-PLGA microstructures of four different sizes showed that the drug release kinetics is dependent on the total surface area available for drug release. The smaller the particle size, the release rate was faster. Two types of microparticles (10microm diameter and 10microm height, and 50microm diameter and 5microm height) showed zero-order release and complete release was observed within 2weeks. The release rate, however, was not exactly proportional to the surface area. Different drugs which were loaded into the same PLGA formulation showed different release profiles. The main difference was on the initial burst release. The overall release profile seems to be similar for different drugs, if the release profile is adjusted to eliminate the burst release. The initial burst release appears to be inversely related to the water-solubility of a drug, i.e., the lower the water-solubility of a drug, the higher the burst release. The hydrogel template method allowed preparation of homogeneous particles with predefined sizes with high drug loading. It allowed study on the effect of size and shape on the drug release kinetics. With the microparticles of homogeneous size and shape, the drug release kinetics can be projected based on the size of microparticles and water-solubility of a drug. The ability of making homogeneous particles is expected to provide better prediction and reproducibility of the drug release property of a given formulation.

Drug-eluting stent for delivery of signal pathway-specific 1,3-dipropyl-8-cyclopentyl xanthine.

1,3-Dipropyl-8-cyclopentyl xanthine (DPCPX) is a highly selective antagonist of the adenosine A(1) receptor (A(1)R). The A(1)R mediates mitogenic effects of adenosine in coronary artery smooth muscle cells (CASMC). DPCPX plays a role as an antimitogen and reduces CASMC proliferation by the blockage of A(1)R. A drug-eluting stent (DES) loaded with DPCPX was prepared. The water solubility of DPCPX is 1.6 microg/mL at pH 3-9, and 38.1 +/- 2.3 microg/mL at pH 11. A series of DPCPX-eluting stents were formulated in polyurethane (PU) films with different dose densities and film thicknesses. The release of DPCPX from the PU-coated stents was nearly linear. The release rate and duration were effectively controlled by adjusting the film thickness with the same drug concentration. The eluted DPCPX from the PU films was effective in preventing CASMC proliferation, regardless of stimulation by 2-chloro-N-6-cyclopentyladenosine (CCPA), a highly selective A(1)R agonist. A(1)R specific antagonist DPCPX was effective in preventing CASMC proliferation and holds great promise for intracoronary delivery from DESs to test the role of the A(1)R signaling pathway for prevention of in-stent restenosis.

The mediating effects of sleep in the relationship between traumatic stress and health symptoms in urban police officers.

OBJECTIVE: Posttraumatic stress symptoms have been associated with increased health problems across numerous studies. Sleep disruption, one of the principal symptoms resulting from traumatic stress, has also been shown to produce health problems. This study explored the hypothesis that the relationship between posttraumatic stress symptoms and health is mediated by sleep problems. METHOD: A sample of 741 police officers were administered measures of traumatic stress symptoms, sleep, health functioning, and somatic symptoms. RESULTS: Traumatic stress symptoms were significantly related to both somatic symptoms (R2 = 0.18, p <.001) and health functioning (R2 = 0.02, p <.01). The relationship between somatic symptoms and traumatic stress symptoms was partially mediated by sleep (p <.001). The relationship between traumatic stress symptoms and health functioning was fully mediated by sleep. CONCLUSIONS: Although design characteristics, such as cross-sectional sampling, limit the inferences that can be drawn, these findings suggest that sleep may serve as an important mediator between traumatic stress and somatic symptoms.

Critical incident exposure and sleep quality in police officers.

OBJECTIVE: Police officers face many stressors that may negatively impact sleep quality. This study compares subjective sleep quality in police officers with that in control subjects not involved in police or emergency services. We examined the effects of critical incident exposure (trauma exposure) and routine (nontraumatic) work environment stressors on sleep quality after controlling for the effects of work shift schedule. METHODS: Subjective sleep disturbances were measured by the Pittsburgh Sleep Quality Index in police officers (variable-shift workers, N = 551; stable day-shift workers, N = 182) and peer-nominated comparison subjects (variable-shift workers, N = 98; stable day-shift workers, N = 232). The main predictor variables were 1) duty-related critical incident exposure to on-line policing and 2) work environment stress related to routine administrative and organizational aspects of police work. RESULTS: Police officers on both variable and stable day shifts reported significantly worse sleep quality and less average sleep time than the two corresponding control groups. Within police officers, cumulative critical incident exposure was associated with nightmares but only weakly associated with poor global sleep quality. In contrast, the stress from officers' general work environment was strongly associated with poor global sleep quality. Sleep disturbances were strongly associated with posttraumatic stress symptoms and general psychopathology. CONCLUSIONS: A large percentage of police officers report disturbances in subjective sleep quality. Although the life-threatening aspects of police work are related to nightmares, the routine stressors of police service seem to most affect global sleep quality in these subjects. These findings may have implications for health and occupational performance.