This work describes uniform polymer coatings allowing for an adjustment of the orifice dimension of vibrating-mesh nozzles and therefore, size of emerging formulation droplets and dried particles, which is of general interest for diverse spray-drying applications. Chemical vapor deposition of poly(p-xylylene) (PPXN) on aperture templates of the B-90 spray-dryer (orifice diameters: ∼4.0μm) caused a reduction of the opening cross-sections of ∼50%. Thus, a more efficient formulation atomization was observed (finer droplets). Likewise, application of PPXN-coated, rather than plain nozzles, resulted in significantly smaller (particle diameter: 1.3 vs. 3.6μm) and narrower distributed (span: ∼1.4 vs. ∼1.8) sildenafil-loaded poly(lactide-co-glycolide) microparticles. Prediction of the size of spray-dried microparticles using the size results of atomized droplets ("residual core method") was shown to be in agreement with the observed values. Formulations prepared with plain and PPXN-coated nozzles exhibited a sustained sildenafil release profile with mean dissolution times of ∼1.5 and ∼4.0h, respectively. Regardless of the starting aperture template, any desired orifice dimension and therefore, dried particle size could be achieved by generating adequate polymer deposits.
Keywords: Chemical vapor deposition; Controlled drug delivery; Parylene coating; Polymeric microparticles; Spray-drying; Vibrating-mesh atomization.
Copyright © 2015 Elsevier B.V. All rights reserved.