Fusion of polymer-coated liposomes and centrifugally spun microfibers as hybrid materials to enhance sustained release

Abstract

Liposomes are employed for the delivery of molecular cargo in several classes of systems. For instance, the embedding of loaded liposomes in polymeric fibrous scaffolds has enabled the creation of hybrid materials that mimic biological membranes. Liposomes with unmodified surfaces have been predominantly integrated into fibers, which leads to instabilities due to interfacial incompatibility. In addition, electrospinning has been almost exclusively employed for fiber fabrication, which limits the potential for scale-up production. Here, we present the fabrication of hybrid biomimetic materials by fusing polymer-coated liposomes to force-spun microfibers to increase the stability of the hybrid materials and enhance the sustained release of the cargo. L-α-Phosphatidylcholine liposomes were coated with chitosan or polyethylene glycol (PEG). The nano-differential scanning calorimetry results confirm that polymer coating does not affect the phase transition temperature (T_m) of the liposomes, where only the model drug, quercetin, reduced T_m. Centrifugal spinning was employed to fabricate hydrophobic polycaprolactone (PCL) microfibers at various polymer concentrations and using various solvents and spinning parameters to increase the yield at the lowest fiber diameter. The highest microfiber production rate obtained occurred at a 20% (w/v) PCL concentration in 50 : 50 (v/v) chloroform and methanol solution with an average fiber diameter of 584.85 ± 26.30 nm. The non-chemical fusion of the polymer-coated liposomes and the fibrous scaffolds was promoted by immersion at T > T_m, under ultrasonication. We hypothesize that the fusion is driven by hydrophobic interactions between the liposomes and the fibers, which merge the materials through the lipid bilayer. The fused hybrid material solved the burst release problem observed when adhering plain liposomes to nanofibers. Both PEG and chitosan yielded a sustained release, where the release rate with the former was faster. These results demonstrate that the fusion of polymer-coated liposomes and microfibers enables more effective blending of the loaded carriers into the polymer microfibers. Ultimately, the fused liposome/microfiber hybrids are stable matrices and enhance the sustained release of molecular cargo.