Abstract
Monodisperse polyvinyl alcohol (PVA) microspheres have been widely used for targeted drug delivery, embolization, and templates. However, the fast and facile fabrication of PVA microspheres with uniform size and internal structure and good sphericity remains a challenge. In this study, the PVA microspheres with uniformity in the size, shape, and internal structure were rapidly fabricated, using single-emulsion droplet templates by an on-chip approach. First, we designed a polydimethylsiloxane (PDMS) microfluidic chip integrated with three functional units, used for the droplet generation, mixing of reagents, and pre-curing of PVA microspheres, respectively. Then, we precisely controlled the generation of PVA aqueous droplets, mixing of reagents, and the gelation rate for the production of high-quality microspheres by adjusting the pH value, flow rate, and the channel structure. The prepared PVA microspheres are characterized with good sphericity, uniform internal structure, and narrow size distribution. The microspheres have good adsorption capacity and recyclability for small-molecule drugs, as demonstrated by the adsorption and desorption of methylene blue (MB). The adsorption behavior is well described by the pseudo-second-order model, and intraparticle diffusion is as fast as the external film diffusion.
Highlights
Monodispersed spherical polymer microspheres play an important role in many fields due to their uniform sizes and structures, such as in controlled release of stored materials [1,2,3], fabrication of cavities or interspaces templates from microspheres [4,5], and selective adsorption or separation of substances as microreactors [6,7]
Polyvinyl alcohol (PVA) is an inexpensive, commonly used, nontoxic, biocompatible polymer, which is rich in hydroxyl groups and can be modified
A flow-focusing structure with a four-way inlet was designed for droplet generation, one of which was injected with a PVA solution, one was for the mixture of GA and HCl solution, and the other two were for the liquid paraffin containing 5 wt.% EM90 as the surfactant
Summary
Monodispersed spherical polymer microspheres play an important role in many fields due to their uniform sizes and structures, such as in controlled release of stored materials [1,2,3], fabrication of cavities or interspaces templates from microspheres [4,5], and selective adsorption or separation of substances as microreactors [6,7]. PVA is frequently used to make films, fibers, microspheres, and so on [8,9,10,11,12,13]. Many methods for preparing PVA microspheres have been reported. Yong et al reported the electro-spray method for producing hydrogel microspheres [14]. Jia et al reported hydrothermally prepared PVA microspheres [15]. Polydispersity of microspheres remains the major issue with these methods. Han et al reported a freeze-thawing method for preparing PVA microspheres [16]. They achieved good uniformity and sphericity, the whole preparation process is long, requiring 60 h. Young et al have demonstrated the use of the UV polymerization method
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