Continuous Polymer Coating/Encapsulation of Submicrometer Particles Using a Solid Hollow Fiber Cooling Crystallization Method

Abstract

Currently, no technique is available to continuously film coat nanosized drug particles with a polymer to produce large amounts of free-flowing coated particles. In this work, Eudragit RL 100 and poly(d,l-lactide-co-glycolide) (PLGA) were chosen as the coating polymers and Cosmo 55 (550 nm silica particles) as a surrogate for drug particles. After determining the cloud point of the polymer solutions by UV spectrophotometry, we adopted the solid hollow fiber cooling crystallization (SHFCC) technique to continuously coat the submicrometer particles with the polymer. In this method the polymer solution containing a suspension of submicrometer particles flows in the lumen of a solid polymeric hollow fiber. Controlled cooling of the polymer solution by a coolant on the shell side of the hollow fibers allows for polymer nucleation on the surface of the particles; the precipitated polymer forms a thin film around the particles, the thickness of which can be varied depending on the operating conditions. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectrometry, laser diffraction spectroscopy, and thermogravimetric analysis were all used to characterize the coatings. The results indicate that a uniformly coated and free-flowing product can be achieved under optimized conditions in the SHFCC and suitable posttreatments. Furthermore, scale-up of the method can be easily accomplished by using a larger SHFCC module containing a much larger number of solid hollow fibers. This method is easily adaptable for coating nanosized drug particles as well.

Continuous preparation of polymer coated drug crystals by solid hollow fiber membrane-based cooling crystallization

“…An evaluation of the crystalline products from the device outlet suggests that the drug crystallized first; the polymer precipitated later and covered the pre-existing drug crystals and the new drug crystals formed. Our earlier studies (Chen et al, 2014a;Chen et al, 2014b;Chen et al, 2015) have shown that Eudragit precipitation is a somewhat slow process regardless of the precipitation technique employed. No free uncoated crystals were visible.…”

“…Details of the relation between cloud point temperature and the ratio of acetone/water are provided in Chen et al (2014a). A cloud point temperature of 15 o C was selected; it is easily achieved in the laboratory for cooling crystallization experiments; correspondingly, the ratio of acetone/water in ml/ml for this cloud point was 2.5/0.5.…”

“…The internal diameter of the FEP tubing was ~ 14 mm. Details describing of the construction of the module can be found in Chen et al (2014a).…”

“…Such a technique was employed recently by us (Chen et al, 2014a) to generate a thin coating of the polymer Eudragit RL 100 or poly (D,L-lactide-co-glycolide) (PLGA) from its solution in acetone on 550 nm submicron silica particles; the silica particles were in suspension which was flowing continuously through the bore of the hollow fine fibers. The polymer coating thickness could be varied by changing the operating conditions.…”

Drug‐Eluting Medical Textiles: From Fiber Production and Textile Fabrication to Drug Loading and Delivery

“…[186] One of the main issues in the controlled drug delivery systems is the initial burst release. There are some strategies applied to the coating procedure, which can help to achieve sustained release over time, such as using microcapsules and adhesives drugs that can adhere to biological tissues for an extended period of time, [183,187] repeated layers of drug coating on fibers using L-B-L deposition, [188] or taking advantage of processes, such as ultrasound, ion-beam, and irradiation. [4,28,189] For instance, Ma et al [183] coated cotton fabrics with a solution comprised of tamoxifen drug microencapsulated in gelatin B and acacia gum as an anti-cancer drug for the treatment of breast cancer.…”