Strontium/Silicon/Calcium-Releasing Hierarchically Structured 3D-Printed Scaffolds Accelerate Osteochondral Defect Repair

Articular cartilage defects are a global challenge, causing substantial disability. Repairing large defects is problematic, often exceeding cartilage's self-healing capacity and damaging bone structures. To tackle this problem, a scaffold-mediated therapeutic ion delivery system is developed. These scaffolds are constructed from poly(ε-caprolactone) and strontium (Sr)-doped bioactive nanoglasses (SrBGn), creating a unique hierarchical structure featuring macropores from 3D printing, micropores, and nanotopologies due to SrBGn integration. The SrBGn-embedded scaffolds (SrBGn-µCh) release Sr, silicon (Si), and calcium (Ca) ions, which improve chondrocyte activation, adhesion, proliferation, and maturation-related gene expression. This multiple ion delivery significantly affects metabolic activity and maturation of chondrocytes. Importantly, Sr ions may play a role in chondrocyte regulation through the Notch signaling pathway. Notably, the scaffold's structure and topological cues expedite the recruitment, adhesion, spreading, and proliferation of chondrocytes and bone marrow-derived mesenchymal stem cells. Si and Ca ions accelerate osteogenic differentiation and blood vessel formation, while Sr ions enhance the polarization of M2 macrophages. The findings show that SrBGn-µCh scaffolds accelerate osteochondral defect repair by delivering multiple ions and providing structural/topological cues, ultimately supporting host cell functions and defect healing. This scaffold holds great promise for osteochondral repair applications.

Finite-element modeling of neuromodulation via controlled delivery of potassium ions using conductive polymer-coated microelectrodes

Objective. The controlled delivery of potassium is an interesting neuromodulation modality, being potassium ions involved in shaping neuron excitability, synaptic transmission, network synchronization, and playing a key role in pathological conditions like epilepsy and spreading depression. Despite many successful examples of pre-clinical devices able to influence the extracellular potassium concentration, computational frameworks capturing the corresponding impact on neuronal activity are still missing.Approach. We present a finite-element model describing a PEDOT:PSS-coated microelectrode (herein, simplyionic actuator) able to release potassium and thus modulate the activity of a cortical neuron in anin-vitro-like setting. The dynamics of ions in the ionic actuator, the neural membrane, and the cellular fluids are solved self-consistently.Main results. We showcase the capability of the model to describe on a physical basis the modulation of the intrinsic excitability of the cell and of the synaptic transmission following the electro-ionic stimulation produced by the actuator. We consider three case studies for the ionic actuator with different levels of selectivity to potassium: ideal selectivity, no selectivity, and selectivity achieved by embedding ionophores in the polymer.Significance. This work is the first step toward a comprehensive computational framework aimed to investigate novel neuromodulation devices targeting specific ionic species, as well as to optimize their design and performance, in terms of the induced modulation of neural activity.

Role of inorganic ions in wound healing: an insight into the various approaches for localized delivery

Recently, the role of inorganic ions has been explored for its wound-healing applications. Ions do play key role in the normal functioning of the skin, including the epidermal barrier property, maintaining redox balance, enzymatic activities, tissue remodeling, etc. The care of chronic wounds is a concern and new cost-effective therapeutic strategies that modulate the wound microenvironment and cell behaviour are needed. First, this review illustrates the ions that play a role in wound healing and their molecular mechanisms that are accountable for modifying the wound. Further, the emerging strategies using metal ions to modulate the healing will be discussed. In this direction, localized delivery of inorganic ions of importance using advanced wound care biomaterials for wound healing applications is discussed.

Fabrication and characterization of Ag- and Ga-doped mesoporous glass-coated scaffolds based on natural marine sponges with improved mechanical properties

Natural marine sponges were used as sacrificial template for the fabrication of bioactive glass-based scaffolds. After sintering at 1050°C, the resulting samples were additionally coated with a silicate solution containing biologically active ions (Ag and Ga), well-known for their antibacterial properties. The produced scaffolds were characterized by superior mechanical properties (maximum compressive strength of 4 MPa) and total porosity of ~80% in comparison to standard scaffolds made by using PU foam templates. Direct cell culture tests performed on the uncoated and coated samples showed positive results in terms of adhesion, proliferation, and differentiation of MC3T3-E1 cells. Moreover, vascular endothelial growth factor (VEGF) secretion from cells in contact with scaffold dissolution products was measured after 7 and 10 days of incubation, showing promising angiogenic results for bone tissue engineering applications. The antibacterial potential of the produced samples was assessed by performing agar diffusion tests against both Gram-positive and Gram-negative bacteria.

Iron oxide nanoparticle-mediated development of cellular gap junction crosstalk to improve mesenchymal stem cells' therapeutic efficacy for myocardial infarction

Electrophysiological phenotype development and paracrine action of mesenchymal stem cells (MSCs) are the critical factors that determine the therapeutic efficacy of MSCs for myocardial infarction (MI). In such respect, coculture of MSCs with cardiac cells has windowed a platform for cardiac priming of MSCs. Particularly, active gap junctional crosstalk of MSCs with cardiac cells in coculture has been known to play a major role in the MSC modification through coculture. Here, we report that iron oxide nanoparticles (IONPs) significantly augment the expression of connexin 43 (Cx43), a gap junction protein, of cardiomyoblasts (H9C2), which would be critical for gap junctional communication with MSCs in coculture for the generation of therapeutic potential-improved MSCs. MSCs cocultured with IONP-harboring H9C2 (cocultured MSCs: cMSCs) showed active cellular crosstalk with H9C2 and displayed significantly higher levels of electrophysiological cardiac biomarkers and a cardiac repair-favorable paracrine profile, both of which are responsible for MI repair. Accordingly, significantly improved animal survival and heart function were observed upon cMSC injection into rat MI models compared with the injection of unmodified MSCs. The present study highlights an application of IONPs in developing gap junctional crosstalk among the cells and generating cMSCs that exceeds the reparative potentials of conventional MSCs. On the basis of our finding, the potential application of IONPs can be extended in cell biology and stem cell-based therapies.

Luminal flow regulates NO and O2(-) along the nephron

Urinary flow is not constant but in fact highly variable, altering the mechanical forces (shear stress, stretch, and pressure) exerted on the epithelial cells of the nephron as well as solute delivery. Nitric oxide (NO) and superoxide (O(2)(-)) play important roles in various processes within the kidney. Reductions in NO and increases in O(2)(-) lead to abnormal NaCl and water absorption and hypertension. In the last few years, luminal flow has been shown to be a regulator of NO and O(2)(-) production along the nephron. Increases in luminal flow enhance fluid, Na, and bicarbonate transport in the proximal tubule. However, we know of no reports directly addressing flow regulation of NO and O(2)(-) in this segment. In the thick ascending limb, flow-stimulated NO and O(2)(-) formation has been extensively studied. Luminal flow stimulates NO production by nitric oxide synthase type 3 and its translocation to the apical membrane in medullary thick ascending limbs. These effects are mediated by flow-induced shear stress. In contrast, flow-induced stretch and NaCl delivery stimulate O(2)(-) production by NADPH oxidase in this segment. The interaction between flow-induced NO and O(2)(-) is complex and involves more than one simply scavenging the other. Flow-induced NO prevents flow from increasing O(2)(-) production via cGMP-dependent protein kinase in thick ascending limbs. In macula densa cells, shear stress increases NO production and this requires that the primary cilia be intact. The role of luminal flow in NO and O(2)(-) production in the distal tubule is not known. In cultured inner medullary collecting duct cells, shear stress enhances nitrite accumulation, a measure of NO production. Although much progress has been made on this subject in the last few years, there are still many unanswered questions.