Shape controllable microgel particles prepared by microfluidic combining external ionic crosslinking

Abstract

Alginate microgels with varied shapes, such as mushroom-like, hemi-spherical, red blood cell-like, and others, were generated by combining microfluidic and external ionic crosslinking methods. This novel method allows a continuous fine tuning of the microgel particles shape by simply varying the gelation conditions, e.g., viscosity of the gelation bath, collecting height, interfacial tension. The release behavior of iopamidol-loaded alginate microgel particles with varied morphologies shows significant differences. Our technique can also be extended to microgels formation from different anionic biopolymers, providing new opportunities to produce microgels with various anisotropic dimensions for the applications in drug delivery, optical devices, and in advanced materials formation.

Alginate droplets pre-crosslinked in microchannels to prepare monodispersed spherical microgels

“…The morphologies of their xerogels further verify these results of Fig. 2 In general, the collection height (h), the distance between the droplets outlet and the liquid surface of the collection bath is also an important parameter for the control of the microgel shape [19]. Fig.…”

“…As mentioned above, such tailed-shapes were usually obtained in the case of external gelation. It is mainly attributed to the deformation of Na-ALG droplets caused by gravity, interfacial tension, impact and tangential stress when the droplets dripped into a collection bath and passed through the interface of oil and aqueous phases [19,[24][25][26]. In contrast, the spherical Ca-ALG microgels with L/D ratios of almost 1.0 were obtained as shown in Fig.…”

“…4, the different heights seem to exert no influence on the shape of the Ca-ALG microgels because all samples show a uniform spherical shape. These results can be attributed to the pre-crosslinking of droplets in the microchannel while similar studies without pre-crosslinking indicated that the height has a large influence on the shape of the microgels [19].…”

“…In addition, the non-spherical fat particles can generate larger viscosities than spherical particles at the same volume fraction [13,18]. In case of their use as drug carriers, non-spherical particles could offer unpredictable degradation profiles due to the irregular shapes and different thicknesses, resulting in uncontrollable drug release profiles [15,19]. In addition, particles with an irregular shape also affect their vascular adherence, circulation time, endocytosis, intracellular trafficking and phagocytosis of the encapsulated drugs [20].…”

Microfluidic production of single micrometer-sized hydrogel beads utilizing droplet dissolution in a polar solvent

“…6(e)). Hydrogel beads with similar shapes have been reported previously, formed by droplet deformation either at the liquid/liquid interface 45,46 or in microchannels. 47,48 Together with these previous reports, the present study demonstrated the possibility for controlling the droplet shape by utilizing the interfaces in multiphase systems.…”