Abstract
Phospholipids constitute biocompatible and safe excipients for pulmonary drug delivery. They can retard the drug release and, when PEGylated, also prolong the residence time in the lung. The aim of this work was to assess the structure and coherence of phospholipid coatings formed by spray drying on hydrophilic surfaces (silica microparticles) on the nanoscale and, in particular, the effect of addition of PEGylated lipids thereon. Scanning electron microscopy showed the presence of nanoparticles of varying sizes on the microparticles with different PEGylated lipid concentrations. Atomic force microscopy confirmed the presence of a lipid coating on the spray-dried microparticles. It also revealed that the lipid-coated microparticles without PEGylated lipids had a rather homogenous coating whereas those with PEGylated lipids had a very heterogeneous coating with defects, which was corroborated by confocal laser scanning microscopy. All coated microparticles had good dispersibility without agglomerate formation, as indicated by particle size measurements. This study has demonstrated that coherent coatings of phospholipids on hydrophilic surfaces can be obtained by spray drying. However, the incorporation of PEGylated lipids in a one-step spray-drying process to prepare lipid coated microparticles with both controlled-release and stealth properties is very challenging.
Highlights
Phospholipids constitute biocompatible and safe excipients for pulmonary drug delivery
The distribution of the dye-labeled lipids over the L1 and P1 lipid coated silica microparticles (LCmPs) was observed by confocal laser scanning microscopy (CLSM), and the particle size distribution was analyzed by laser diffraction
The effect of polyethylene glycol (PEG) on the surface properties and performance of the lipid-coated microparticles. Both the morphology images obtained with scanning electron microscopy (SEM) and height images obtained with tapping mode atomic force microscopy (AFM) demonstrated that the size of the nanoparticles on the LCmPs increased with the presence of PEGylated lipids
Summary
Phospholipids constitute biocompatible and safe excipients for pulmonary drug delivery They can retard the drug release and, when PEGylated, prolong the residence time in the lung. Phospholipids, which constitute the main components of endogenous lung surfactants, are promising multifunctional excipients that are considered as biocompatible and safe for pulmonary drug delivery They are amphiphilic molecules composed of a hydrophilic head group and (a) hydrophobic tail(s). The application of phospholipids as excipients can aid the delivery of drugs to the lungs as they are able to improve particle migration to the lung periphery due to the reduction in surface tension [7] Their low aqueous solubility, resulting from the long hydrophobic tails, can help controlling drug dissolution and release. The coating quality and surface structure of the coated or encapsulated particle greatly affect its dissolution [9,35], this has never been investigated due to the difficulty of studying the surface structure of a micronized particle on a nanoscale level
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