RESUMO
Inflammatory bowel disease (IBD) is mediated by an overexpression of tumor necrosis factor-α (TNF) by mononuclear cells in the intestinal mucosa. Intravenous delivery of neutralizing anti-TNF antibodies can cause systemic immunosuppression, and up to one-third of people are non-responsive to treatment. Oral delivery of anti-TNF could reduce adverse effects; however, it is hampered by antibody degradation in the harsh gut environment during transit and poor bioavailability. To overcome these shortcomings, we demonstrate magnetically powered hydrogel particles that roll along mucosal surfaces, provide protection from degradation, and sustain the local release of anti-TNF. Iron oxide particles are embedded into a cross-linked chitosan hydrogel and sieved to produce 100-200 µm particles called milliwheels (m-wheels). Once loaded with anti-TNF, these m-wheels release 10 to 80% of their payload over 1 week at a rate that depends on the cross-linking density and pH. A rotating magnetic field induces a torque on the m-wheels that results in rolling velocities greater than 500 µm/s on glass and mucus-secreting cells. The permeability of the TNF-challenged gut epithelial cell monolayers was rescued in the presence of anti-TNF carrying m-wheels, which both neutralized the TNF and created an impermeable patch over leaky cell junctions. With the ability to translate over mucosal surfaces at high speed, provide sustained release directly to the inflamed epithelium, and provide barrier rescue, m-wheels demonstrate a potential strategy to deliver therapeutic proteins for the treatment of IBD.
RESUMO
For targeted transport in the body, biomedical microbots (µbots) must move effectively in three-dimensional (3D) microenvironments. Swimming µbots translate via asymmetric or screw-like motions while rolling ones use friction with available surfaces to generate propulsive forces. We have previously shown that planar rotating magnetic fields assemble µm-scale superparamagnetic beads into circular µbots that roll along surfaces. In this, gravity is required to pull µbots near the surface; however, this is not necessarily practical in complex geometries. Here we show that rotating magnetic fields, in tandem with directional magnetic gradient forces, can be used to roll µbots on surfaces regardless of orientation. Simplifying implementation, we use a spinning permanent magnet to generate differing ratios of rotating and gradient fields, optimizing control for different environments. This use of a single magnetic actuator sidesteps the need for complex electromagnet or tandem field setups, removes requisite gravitational load forces, and enables µbot targeting in complex 3D biomimetic microenvironments.
RESUMO
For disease of the lung, the physical key to effective inhalation-based therapy is size; too large (10's of µm) and the particles or droplets do not remain suspended in air to reach deep within the lungs, too small (subµm) and they are simply exhaled without deposition. µBots within this ideal low-µm size range however are challenging to fabricate and would lead to devices that lack the speed and power necessary for performing work throughout the pulmonary network. To uncouple size from structure and function, here we demonstrate an approach where individual building blocks are aerosolized and subsequently assembled in situ into µbots capable of translation, drug delivery, and mechanical work deep within lung mimics. With this strategy, a variety of pulmonary diseases previously difficult to treat may now be receptive to µbot-based therapies.
RESUMO
Within the last decade, interest in using biphasic systems for producing furans from biomass has grown significantly. Biphasic systems continuously extract furans into the organic phase, which prevents degradation reactions and potentially allows for easier separations of the products. Several heterogeneous catalyst types, including zeolites, ion exchange resins, niobium-based, and others, have been used with various organic solvents to increase furan yields from sugar dehydration reactions. In this minireview, we summarized the use of heterogeneous catalysts in biphasic systems for furfural and 5-hydroxymethylfurfural production from the past five years, highlighting trends in chemical and physical properties that effect catalytic activity. Additionally, the selection of an organic solvent for a biphasic system is extremely important and we review and discuss properties of the most commonly used organic solvents.
