Laser Direct Writing of Flexible Thermal Flow Sensors.

Thin film-based thermal flow sensors afford applications in healthcare and industries owing to their merits in preserving initial flow distributions. However, traditional thermal flow sensors are primarily applied to track flow intensities based on hot-wire or hot-film sensing mechanisms due to their relatively facile device configurations and fabrication strategies. Herein, a calorimetric thermal flow sensor is proposed based on laser direct writing to form laser-induced graphene as heaters and temperature sensors, resulting in monitoring both flow intensities and orientations. Via homogeneously surrounding spiral heaters with multiple temperature sensors, the device exhibits high sensitivity (∼162 K·s/m) at small flows with an extended flow detection range (∼25 m/s). Integrating the device with a data-acquisition board and a dual-mode graphical user interface enables wirelessly and dynamically monitoring respiration and the motion of robotic arms. This versatile flow sensor with facile manufacturing affords potentials in health inspection, remote monitoring, and studying hydrodynamics.

Drug Release Property of Poly 3-Hydroxybutyrate 4-Hydroxybutyrate (P34HB) as Drug-Eluting Coatings on Metal Coronary Stents.

Drug-eluting stents (DES) have become the main method of interventional therapy for coronary heart disease, because their drug coating can effectively reduce the incidence of restenosis after stent implantation. Biodegradable polymers for coatings are the latest development direction for coating polymers, because they can be degraded into small molecules in the human body. In this study, the polymer P34HB(P34HB-1:4HB% = 1 mol%, Mw: 225,000; P34HB-10:4HB% = 10 mol%, Mw: 182,000), the fourth generation of biodegradable Polyhydroxy alkanoates (PHAs), was coated on stents to evaluate the drug release properties of the DES. Both P34HB-1 and P34HB-10 coatings showed increased drug release rates, as the polymer concentrations were gradually increased from 8 mg/mL to 28 mg/mL. Both P34HB-1 and P34HB-10 coatings showed increased drug release rates as the drug polymer ratios were gradually changed from 1:10 to 1:2. The drug release rates of the P34HB-1 coatings became slower than P34HB-10, thus showing sustained drug release effects. The drug release rates of the P34HB-1 coatings decreased when Rates of solution flow increased, decreased when Focusing pressures decreased, and decreased when Mandrel moving speeds increased. P34HB-1 coatings prepared with CHCl3/NPA (10:1) mixed solvents had better controlled drug release rates compared to Firebird2®. The drug release rates of P34HB-1 coatings prepared with CHCl3 solutions decreased as the outer layer weights were increased from 0 to 800 µg. When the outer layer weights reached 800 µg, the drug release rates of P34HB-1 coatings were slower than Firebird2®. P34HB-1 coatings prepared with both CHCl3/NPA (10:1) mixed solvents and double layers had more effectively controlled drug release rates than P34HB-1 coatings prepared with only mixed solvents or double layers and these effects were far greater than Firebird2@; thus, P34HB-1 represents a latent polymer for DES.

Poly 3-Hydroxybutyrate 4-hydroxybutyrate (P34HB) as a Potential Polymer for Drug-Eluting Coatings on Metal Coronary Stents.

Drug-eluting stents (DES) are a main interventional therapeutic instrument to treat coronary diseases. Degradable polymers such as polylactic acid (PLA) for coatings that only degrade into small molecules in human bodies have been developed for coating polymers, but most coatings often lack ductility and can be easily peeled off from the stents after balloon expansion. In this study, biodegradable poly 3-hydroxybutyrate 4-hydroxybutyrate (P34HB) with good ductility was proposed to be a latent polymer for drug-eluting coatings on the stents. Using P34HB-1 (4HB% = 1%wt, Mw: 225,000) and P34HB-10 (4HB% = 10%wt, Mw: 182,000) as two candidates, both P34HB-1 and P34HB-10 exhibited excellent solubility in CHCl3. Their drug solutions remained highly stable and did not become turbid over a period of 48 h, and were conducive to batch preparation of uniform drug coatings. Drug coatings made by both P34HB-1 and P34HB-10 on the stents were almost complete before and after dilation by balloon owing to their excellent adhesion and extrusion resistance properties. Furthermore, both P34HB-1 and P34HB-10 had excellent biocompatibility in cytotoxicity and hemolysis tests. However, P34HB-1 drug coatings showed better drug release control than P34HB-10 drug coatings and Firebird2®, indicating that P34HB-1 is more suitable for a latent coating polymer of coronary stents.