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
Biomaterial controlled osteoinduction is influenced by the porous microenvironment and the composition of incorporated calcium orthophosphate (CaPi) polymorphs, however, for the design of materials that rival the efficacies of natural grafts a systematic approach to assessing the physicochemical properties that affects cellular differentiation is needed. In this research, we introduce a bioinspired synthetic approach to the mineralization of preformed porous collagen hydrogel scaffolds with tunable apatite coatings. Initially, collagen scaffolds are mineralized with dicalcium phosphate dihydrate (DCPD) by alternate immersion in Ca2+ and HPO42- salt solutions. Utilizing classic DCPD conversion chemistry, the surface coatings are selectively transformed to apatite by immersion of the DCPD-collagen substrate in Tris buffer at pH 7.4, 37°C, for 5 days. The composition and morphology of the deposited mineral coatings are characterized by XRD, SEM, and AFM. Variations in the porous microarchitecture of the collagen hydrogel substrate, pore size (9.5 ± 5 µm, 165 ± 50 µm) and pore alignment altered the morphology of the deposited apatite particles. Intrafibrillar and extrafibrillar mineralization of the collagen templates were observed for both investigated pore sizes. However, templates with aligned pores of both sizes were observed to restrict intrafibrillar mineralization resulting in the exclusive deposition of surface coatings. The osteoinductive activity of the apatite-collagen materials with varied pore microarchitectures was evaluated by in vitro culture of human mesenchymal stem cells for 28 days based on cellular proliferation, alkaline phosphatase activity, and the expression of RUNX2. The combined effects of apatite coatings, reduced pore size, and pore alignment contributed to reductions in cellular proliferation. However, the apatite mineral coating was determined to induce high levels of RUNX2 expression in the absence of additional osteoinductive agents, indicative of biomaterial-induced osteogenesis. This work establishes a versatile synthetic platform for the preparation of bone-like apatite collagen materials with osteoinductive activity.