One of the main routes to ensure that biomolecules or bioactive agents remain active as they are incorporated into products with applications in different industries is by their encapsulation. Liposomes are attractive platforms for encapsulation due to their ease of synthesis and manipulation and the potential to fuse with cell membranes when they are intended for drug delivery applications. We propose encapsulating our recently developed cell-penetrating nanobioconjugates based on magnetite interfaced with translocating proteins and peptides with the purpose of potentiating their cell internalization capabilities even further. To prepare the encapsulates (also known as magnetoliposomes (MLPs)), we introduced a low-cost microfluidic device equipped with a serpentine microchannel to favor the interaction between the liposomes and the nanobioconjugates. The encapsulation performance of the device, operated either passively or in the presence of ultrasound, was evaluated both in silico and experimentally. The in silico analysis was implemented through multiphysics simulations with the software COMSOL Multiphysics 5.5^® (COMSOL Inc., Stockholm, Sweden) via both a Eulerian model and a transport of diluted species model. The encapsulation efficiency was determined experimentally, aided by spectrofluorimetry. Encapsulation efficiencies obtained experimentally and in silico approached 80% for the highest flow rate ratios (FRRs). Compared with the passive mixer, the in silico results of the device under acoustic waves led to higher discrepancies with respect to those obtained experimentally. This was attributed to the complexity of the process in such a situation. The obtained MLPs demonstrated successful encapsulation of the nanobioconjugates by both methods with a 36% reduction in size for the ones obtained in the presence of ultrasound. These findings suggest that the proposed serpentine micromixers are well suited to produce MLPs very efficiently and with homogeneous key physichochemical properties.

Research in nanostructured materials has led to the development of different applications of relevance in the fields of medicine and biomedical engineering. In this regard, the field of drug delivery has probably benefited the most due to the possibility to engineer vehicles of high potency and increased activity and selectivity toward selected intracellular targets. Such vehicles can therefore potentially address one of the major cornerstones of modern pharmacology, which is increasing the bioavailability of drugs of low permeability. Our research group has developed cell-penetration nanobioconjugates by interfacing several nanomaterials (e.g., chitosan, gelatin nanoparticles, graphene oxide, and magnetite) with translocating peptides. The obtained nanobioconjugates have demonstrated facilitated cell internalization and endosomal escape abilities. To improve cell penetration even further, we encapsulated the magnetite-based nanobioconjugates into liposomes (to form magnetoliposomes) with very appealing results. Our plan is to expand the available nanoplatforms by combining the attributes of magnetite and polymeric nanoparticles through a core-shell system comprised of magnetite (core) and chitosan (shell). The encapsulation process has been successfully accomplished with the aid of passive micromixers with different channel geometries to favor intimate contact between the dispersed phase (nanoparticles) and the continuous phase (phospholipid solution). To model the encapsulation process, we implemented an Eulerian simulation in the software COMSOL Multiphysics^® 6.0 (COMSOL Inc, Stockholm, Sweden) where mixing required the Navier-Stokes equations as governing equations of momentum transport, turbulence, eddy viscosity, and damping functions to approximate turbulence using the κ-ε turbulence model near the walls. The simulation was conducted for the different geometries (i.e., SARS, chambers, and serpentine) and for Reynolds numbers ranging from 0.2 to 10 Also, we tested a low Reynolds turbulent model using the κ-ε model given in the Euler-Euler module. The Euler-Euler approach showed that the encapsulation reaches higher encapsulation efficiency (EE%) values compared with the previously implemented mixture model. Our encapsulation results indicate that including the κ-ε turbulence model with a low Reynolds turbulence model near the walls provides a higher agreement between in-silico and experimental approaches. Future work will be dedicated to evaluating the performance of our previously tested magnetophoretic separators with the newly developed encapsulates, to assure sufficient purity for further biocompatibility testing.

The delivery of bioactive compounds is often improved by their encapsulation within systems based on different materials, such as polymers and phospholipids. In this regard, one of the most attractive vehicles are liposomes, which can be produced by the self-assembly of phospholipids in aqueous buffered systems. Encapsulation of therapeutic magnetite nanoparticles (MNPs) within liposomes can be accomplished by direct translocation of their lipid bilayer by surface conjugation of potent translocating peptides (and proteins) such as Buforin-II and OmpA. Here, we put forward the notion that to achieve reproducibility and optimize this process, it is possible to develop microfluidic systems that use flow-focusing methods to manipulate the interaction of suspended MNPs (ferrofluids) with the liposomes. With that in mind, we have developed an in silico approach to predict the performance of microfluidic devices specifically designed for the encapsulation process. This was done by running multiphysics simulations in COMSOL to evaluate the macroscopic flow of liposomes and suspended MNPs via a multiphase mixture model. Moreover, we estimated the corresponding interaction using a chemical reaction model based on embedding the Michaelis–Menten equation within the diluted species module’s transport. In this case, the enzymes-substrate interaction was considered similar to that of the MNPs-liposome. As a result, we were able to approach saturation kinetics that resemble that obtained experimentally for the uptake of functionalized MNPs. Future work will be directed towards refining the model by considering more details on the possible stages during the interaction of the involved intermediates.

Endothelialization is required to maintain patency in tissue-engineered vascular grafts (TEVGs). Ligand surface functionalization is intended to induce the adhesion and spreading of Endothelial Cells (ECs). ECs surface adhesion occurs through the integrin-ligand interaction. Here, we propose a chemo-mechanical model, using COMSOL Multiphysics 5.5, to study the optimal ligand distribution in order to improve interaction under laminar blood flow. The proposed model elucidates the role of binding forces and flow velocities over cell spreading as a function of the relevant ligand concentration. This model can contribute to optimizing the surface functionalization of TEVGs for promoting successful endothelialization.