Analysis of the diffusion process by pH indicator in microfluidic chips for liposome production

In recent years, the development of nano- and micro-particles has attracted considerable interest from researchers and enterprises, because of the potential utility of such particles as drug delivery vehicles. Amongst the different techniques employed for the production of nanoparticles, microfluidic-based methods have proven to be the most effective for controlling particle size and dispersity, and for achieving high encapsulation efficiency of bioactive compounds. In this study, we specifically focus on the production of liposomes, spherical vesicles formed by a lipid bilayer encapsulating an aqueous core. The formation of liposomes in microfluidic devices is often governed by diffusive mass transfer of chemical species at the liquid interface between a solvent (i.e., alcohol) and a non-solvent (i.e., water). In this work, we developed a new approach for the analysis of mixing processes within microfluidic devices. The method relies on the use of a pH indicator, and we demonstrate its utility by characterizing the transfer of ethanol and water within two different microfluidic architectures. Our approach represents an effective route to experimentally characterize diffusion and advection processes governing the formation of vesicular/micellar systems in microfluidics, and can also be employed to validate the results of numerical modelling

Complexation to cationic microspheres of double-stranded peptide nucleic acid-DNA chimeras exhibiting decoy activity

The major aim of this paper was to determine whether cationic microspheres (CM), consisting of the permeable polymer Eudragit\uc2\uae RS 100 plus the cationic surfactant dioctadecyl-dimethyl-ammonium bromide (DDAB18), could bind to double-stranded peptide nucleic acid PNA-DNA-PNA (PDP) chimeras exhibiting decoy activity against NF-\uce\ubaB transcription factors. Microspheres were produced by the 'solvent evaporation method' and centrifugation at 500, 1,000 and 3,000 rpm to obtain different-sized microparticles. Microsphere morphology, size and size distribution were determined by optical and electron microscopy observations. In order to determine their binding activity, double-stranded DNA-based and PDP-based decoy molecules were incubated with different amounts of microparticles in the presence of 100 ng of either32P-labeled DNA-DNA or DNA-PDP hybrid molecules or cold PDP-PDP hybrids. The complexes were analyzed by agarose gel electrophoresis. The resistance of32P-labeled DNA-DNA and DNA-PDP molecules in the presence of serum or cellular extracts was evaluated after binding to CM by gel electrophoresis analysis. DDAB18Eudragit RS 100 microspheres are able to bind to DNA-PDP and PDP-PDP hybrids, to deliver these molecules to target cells and to protect DNA-PDP molecules from enzymatic degradation in simulated biological fluids. In addition, when assayed in ex vivo conditions, DDAB18Eudragit RS 100 microspheres exhibited low toxicity. The results presented in this paper demonstrate that CM can be considered suitable formulations for pharmacogenomic therapy employing double-stranded PDP chimeras

DoE Analysis of Approaches for Hydrogel Microbeads' Preparation by Millifluidic Methods

Hydrogel microbeads hold great promise for immune-protective cell transplants and in vitro studies. Millifluidic generation of hydrogel microbeads is a highly efficient and reproducible approach enabling a mass production. This paper illustrates the preparation and characterization of highly controlled and reproducible microbeads made by different types of hydrogel using millifluidic approaches. The optimization of the process was made by a design of experiments (DoE) approach. The microbeads' large-scale production can be potentially used for single cells or clusters encapsulation

Dedifferentiated Chondrocytes in Composite Microfibers As Tool for Cartilage Repair.

Tissue engineering (TE) approaches using biomaterials have gain important roles in the regeneration of cartilage. This paper describes the production by microfluidics of alginate-based microfibers containing both extracellular matrix (ECM)-derived biomaterials and chondrocytes. As ECM components gelatin or decellularized urinary bladder matrix (UBM) were investigated. The effectiveness of the composite microfibers has been tested to modulate the behavior and redifferentiation of dedifferentiated chondrocytes. The complete redifferentiation, at the single-cell level, of the chondrocytes, without cell aggregate formation, was observed after 14 days of cell culture. Specific chondrogenic markers and high cellular secretory activity was observed in embedded cells. Notably, no sign of collagen type 10 deposition was determined. The obtained data suggest that dedifferentiated chondrocytes regain a functional chondrocyte phenotype when embedded in appropriate 3D scaffold based on alginate plus gelatin or UBM. The proposed scaffolds are indeed valuable to form a cellular microenvironment mimicking the in vivo ECM, opening the way to their use in cartilage TE

Preparation of microspheres based on alginate/agarose blends by microfluidic technique

The paper reports the preparation of microspheres based on alginate/agarose blends by microfluidic techniqu

Tunable and Reversible Gelatin-Based Bonding for Microfluidic Cell Culture

The development of novel bonding techniques could enable new applications and uses of plastics in microfluidic cell culture, complementing the omnipresent polydimethylsiloxane (PDMS). In this respect, the present paper describes a reversible gelatin-based method (named GEL-D) for bonding microfluidic chip parts, constituted of different materials. The herein introduced method enables the bonding of the most of the commonly used materials in microfluidics such as PMMA, PDMS, glass and NOA. Notably, the fabricated chips resist to pressure up to 0.7 MPa, to organic solvent exposure and temperature up to 70 °C. To show the versatility of the described method, microchips with different sizes, materials, and geometries were bonded, including microchannel down to 200 µm (width x depth) and round microstructures. The bonded chips are suitable to microfluidic cell culture procedures, including formation of microtissues, cells viability analysis and confocal microscopy. Therefore, the room-temperature bonding method appear to be highly efficient for cell culture on plastic chips, where in situ analysis of the seeded cells is required after microchip de-bonding

Physico-chemical characterization of Ca-alginate microparticles produced with different methods

In the present paper the physico-chemical characterization of Ca-alginate microparticles produced with different methods is presented. Ca-alginate microparticles were obtained either by emulsification method or by dripping an aqueous alginate solution into a solution of calcium salt. Inverse Size Exclusion Chromatography (ISEC) was used for the determination of dimensions of the pores and porous volume of microparticles having a mean diameter of 220 ?m when obtained by emulsification method