Modified vibrating-mesh nozzles for advanced spray-drying applications

•Nozzle elements of the B-90 spray-dryer were coated by uniform polymer films.•Adjustment of orifice dimensions resulted in a more efficient formulation atomization (finer droplets).•Modified nozzle elements generated smaller particles with modified release properties.•Adequate polymer deposits would allow for powder fabrication matching the needs of the individual application.•Polymer coated nozzles reveal significant potential for a number of other applications in chemistry and medicine.

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: ∼4.0 μm) 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. 3.6 μm) 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 ∼4.0 h, respectively.Regardless of the starting aperture template, any desired orifice dimension and therefore, dried particle size could be achieved by generating adequate polymer deposits.

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