Mesenchymal stem cells (MSCs) have been widely studied as a versatile cell source for tissue regeneration and remodeling due to their potent bioactivity, which includes modulation of inflammation response, macrophage polarization toward proregenerative lineage, promotion of angiogenesis, and reduction in fibrosis. This review focuses on profiling the effects of paracrine signals of MSCs, commonly referred to as the secretome, and highlighting the various engineering approaches to tune the MSC secretome. Recent advances in biomaterials‐based therapeutic strategies for delivery of MSCs and MSC‐derived secretome in the form of extracellular vesicles are discussed, along with their advantages and challenges.

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ABSTRACT:Particulate platforms capable of delivering multiple actives while providing diagnostic features have gained considerable interest over the last few years. In this study, magnetic polymer yolkshell particles (YSPs) were engineered using a tri-needle coaxial electrospraying technique enabling dual-mode (ultrasonic and magnetic resonance) imaging capability with specific multidrug compartments via an advanced single-step encapsulation process. YSPs comprised magnetic Fe 3 O 4 nanoparticles (MNPs) embedded in the polymeric shell, an interfacing oil layer and a polymeric core (i.e. composite shell-oil interface-polymeric core). Ultrasound backscatter signal frequency was modulated through YSP loading dosage, and both T 1 and T 2 weighted MRI signal intensities were shown to reduce with increasing MNP content (YSP outer shell). Three fluorescent dyes (selected as model probes with varying hydrophobicities) were co-encapsulated separately to confirm YSP structure. Probe release profiles were tuned by varying power or frequency of an external auxillary magnetic field (AMF, 0.7 mT (LAMF) or 1.4 mT (HAMF)).In addition, an "inversion" phenomenon for AMF-enhanced drug release process was captured and is reported. Low YSP cytotoxicity (5mg/ml) and biocompatibility (murine, L929) was confirmed. In summary, magnetic YSPs demonstrate timely potential as multifunctional theranostic agents for dual-imaging modality and magnetically controlled co-active delivery.

Topography and surface morphology of micrometer and nanometer scaled fibrous biomaterials are crucial for bioactive component encapsulation, release, promoting cell proliferation and interaction within biological environment. Specifically, for drug delivery and tissue repair applications, surface engineering provides control on both aspects in tandem. In this study, the bioactive component (ganoderma lucidum spore polysaccharide (GLSP)) was loaded into zein prolamine (ZP) fiber matrices via coaxial electrospinning (CES) technique. During the CES process, various outer layer enveloping fluids were used to modulate fiber topography in-situ (from 2D to 3D). SEM and water contact angle tests indicate enveloping media impact electrospun fiber diameter (ranging from 400 nm to 3.0 μm) and morphologies (from flat ribbon-like to solid cylindrical structures), with the latter impacting GLSP release profile. Furthermore, CCK-8 assay assessment indicates fibroblast cell proliferation (L929 cell line), while cell extension was also observed for modified ZP fibers. The results demonstrate potential applications of modified fiber morphologies, which are tailored in-situ without impacting chemical stability and encapsulation.