Low Modulus Biomimetic Microgel Particles with High Loading of Hemoglobin

Abstract

We synthesized extremely deformable red blood cell-like microgel particles and loaded them with bovine hemoglobin (Hb) to potentiate oxygen transport. With similar shape and size as red blood cells (RBCs), the particles were fabricated using the PRINT® (Particle Replication In Non-wetting Templates) technique. Low crosslinking of the hydrogel resulted in very low mesh density for these particles, allowing passive diffusion of hemoglobin throughout the particles. Hb was secured in the particles through covalent conjugation of the lysine groups of Hb to carboxyl groups in the particles via EDC/NHS coupling. Confocal microscopy of particles bound to fluorescent dye-labeled Hb confirmed the uniform distribution of Hb throughout the particle interior, as opposed to the surface conjugation only. High loading ratios, up to 5 times the amount of Hb to polymer by weight, were obtained, without a significant effect on particle stability, shape, though particle diameter decreased slightly with Hb conjugation. Analysis of the protein by circular dichroism (CD) spectroscopy showed that the secondary structure of Hb was unperturbed by conjugation to the particles. Methemoglobin in the particles could be maintained at a low level and the loaded Hb could still bind oxygen as studied by UV-vis spectroscopy. Hb-loaded particles with moderate loading ratios demonstrated excellent deformability in microfluidic devices, easily deforming to pass through restricted pores half as wide as the diameter of the particles. The suspension of concentrated particles with Hb concentration of 5.2 g/dL showed comparable viscosity to that of mouse blood, and the particles remained intact even after being sheared at a constant high rate (1,000 1/s) for 10 min. Armed with the ability to control size, shape, deformability, and loading of Hb into RBC mimics, we will discuss the implications for artificial blood.

Biodegradable colloidal microgels with tunable thermosensitive volume phase transitions for controllable drug delivery

“…Biodegradability is one of the most important considerations of scaffolds for tissue engineering. However, the use of PNIPAMbased microgels (including nanogels) as carriers for drug delivery has been limited by their insufficient biocompatibility and biodegradability [17], which may result in accumulation in the body for longer duration that trigger cytotoxicity [18,19], and hindrance of microcirculation [20]. Furthermore, high aggregation of the PNIPAM microgels in aqueous environments, due to their hydrophobic surfaces at temperature above LCST, has been a major barrier for the drug delivery applications.…”

Engineered PRINT® nanoparticles for controlled delivery of antigens and immunostimulants

“…6,8,11,13,14 This allowed functionalization of PRINT particles with specific antibodies for targeted delivery. 28 Overall compatibility of PRINT process with immunoglobulins 11,28 suggests that PRINT particles can be used to deliver pathogen-specific antibodies for passive immunity applications or enhance delivery of the current antibody therapies used for immunosuppression.…”

Red blood cells: Supercarriers for drugs, biologicals, and nanoparticles and inspiration for advanced delivery systems

“…Moreover, PRINT® sRBCs were designed to harbor hemoglobin and were shown to possess oxygen binding capacity (Fig. 5d) [175]. PRINT® sRBCs were also engineered to possess functions that natural RBCs do not have, namely, pH-modulated swelling (Fig.…”

“…(a–c) Reprinted from [168]. (d) Adapted with permission from [175]. Copyright (2012) American Chemical Society.…”