Microfluidic encapsulation of nanoparticles in alginate microgels gelled via competitive ligand exchange crosslinking.

Efficient delivery of nanometric vectors complexed with nanoparticles at a target tissue without spreading to other tissues is one of the main challenges in gene therapy. One means to overcome this problem is to confine such vectors within microgels that can be placed in a target tissue to be released slowly and locally. Herein, a conventional optical microscope coupled to a common smartphone was employed to monitor the microfluidic production of monodisperse alginate microgels containing nanoparticles as a model for the encapsulation of vectors. Alginate microgels (1.2%) exhibited an average diameter of 125 ± 3 µm, which decreased to 106 ± 5 µm after encapsulating 30 nm fluorescent nanoparticles. The encapsulation efficiency was 70.9 ± 18.9%. In a 0.1 M NaCl solution, 55 ± 5% and 92 ± 4.7% of nanoparticles were released in 30 minutes and 48 hours, respectively. Microgel topography assessment by atomic force microscopy revealed that incorporation of nanoparticles into the alginate matrix changes the scaffold's interfacial morphology and induces crystallization with the appearance of oriented domains. The high encapsulation rate of nanoparticles, alongside their continuous release of nanoparticles over time, makes these microgels and the production unit a valuable system for vector encapsulation for gene therapy research.

Hybrid microgels produced via droplet microfluidics for sustainable delivery of hydrophobic and hydrophilic model nanocarriers.

Drug delivery for treatment of chronic diseases relies on the effective delivery of payload materials into the target cells in a long-term release. In this context, the present study investigated hybrid microgels as platforms to carry nanoparticles to drug delivery. Hybrid microgels were produced with silk fibroin (SF) and chondroitin sulfate (CS), and alginate (ALG) by droplet microfluidics. ALG/SF, ALG/CS, and ALG/CS/SF microgels, ranging from 70-90 µm, were tested to encapsulate two model nanoparticles, polystyrene latex beads in pristine form (NPs) and NPs coated with bovine serum albumin (NPs-BSA) to simulate hydrophobic and hydrophilic nanocarriers, respectively. IR spectroscopy and fluorescence microscopy analysis confirmed the presence of SF and CS within ALG-based microgels revealing marked differences in their morphology and physicochemical properties. The release profiles of model nanoparticles revealed to be dependent on microgels composition and physicochemical properties. These findings show that SF ternary hybrid microgels facilitated the entrapment of hydrophobic nanocarriers with encapsulation efficiency (EE) from 83 to 98% keeping a better sustainable profile release than nonhybrid ALG microgels. Besides, CS improved the carriage of NPs-BSA (EE = 85%) and their profile release. The results highlight the versatility and tunable properties of these biobased microgels, being a good strategy to be used as an efficient platform in using macro and nanoencapsulated systems for drug delivery.

Droplet-Based Microfluidics Methods for Detecting Enzyme Inhibitors.

Sub-nanoliter droplets produced in microfluidic devices have gained an enormous importance for performing all kinds of biochemical assays. One of the main reasons is that the amounts of reagents employed can be reduced in approximately five orders of magnitude compared to conventional microplate assays. In this chapter, we describe how to carry out the design, fabrication, and operation of a microfluidic device that allows performing enzyme kinetics and enzyme inhibition assays in droplets. This procedure can be used effectively to screen a small size library of compounds. Then, we describe how to use this droplet microfluidic setup to screen for potential inhibitor compounds eluted from a coupled high-performance liquid chromatography (HPLC) system that separates crude natural extracts.