Blood collection and processing are two major steps in pre-analytical laboratory testing. Proper blood collection and timely processing by well-trained staff using appropriate devices are needed to ensure test reliability. Blood collection devices have been typically regarded as inert specimen carriers. Blood collection tubes are comprised of rubber stoppers, tube wall materials, surfactants, anticoagulants, separator gels, clot activators, anticoagulants, and surfactants.
Ultrasonic Spray Nozzles with extended horns have are used for coating of the inside of both evacuated and non-evacuated blood collection tubes (VBCT & BCT), with anticoagulants (EDTA K2, EDTA K3, Lithium Heparin, Sodium Heparin) ,and Blood Clotting Accelerants (Silica, Thrombin, Venom). Ultrasonic technology has its advantages over conventional air systems due to its low velocity, air-less spray that can easily be controlled to coat targeted areas within devices and well as enabling layering of coatings. Other advantages to ultrasonic spray technology for VBCT & BCT include: High transfer efficiency resulting in consistent quantities of deposited reagents and lower costs of manufacturing. Manufacturing process validation (GMP, ISO 13485, etc) is made easier with consistent reagent deposition. Perfect for solvent free processes, which are non-hazardous, lower cost, and environmentally friendly.
Polymer coatings containing drugs released over time are used to inhibit restenosis in bare-metal stents; however applying coatings to stents, which have intricate geometries, is challenging. Ultrasonic atomizing spray nozzles can be effective in achieving continuous and uniform coatings.
The polymer/drug matrix allows the drug to be released (eluted) slowly, over a period of several months, thereby inhibiting the formation of cell masses, and hence significantly reducing the probability of restenosis. Clinical trials using drug-eluting stents have shown that the occurrence of restenosis could be reduced dramatically compared with a rate in the order of 25% for uncoated stents.
Dip coating is not a viable alternative because of tight stent geometry. The spacing between struts, particularly where they join each other, can be as small as 50 µm. Dip coating would result in the bridging of these areas, something that is not allowed, because the bridged coating could eventually break off and enter the blood stream. Even spray-coated stents can exhibit bridging if not processed properly.
Coating arterial stents is a challenging application. Ultrasonic spray nozzles are ideally suited to the application because they are capable of producing low flow rates, when spraying expensive materials such as drugs in a polymer solvent solutions such as Sirolimus (Rapamycin) and Paclitaxel.precisely shaped spray patterns, low-velocity delivery, and relatively small drops. The techniques used in coating may vary, as may the drug/polymer system. These variances make it important to optimise the entire system for each specific circumstance.
ultrasonic spray coatings can replace traditional dip coating methods for parts such as guide wires, catheters and hypo-tubes resulting in less waste, improved concentricity and longitudinal uniformity. Additionally, due to the accurate spray pattern characteristics, excellent edge definition can be achieved allowing for the elimination of costly masking on medical devices.