Softer Zwitterionic Nanogels for Longer Circulation and Lower Splenic Accumulation

Zwitterionic nanogels of varying stiffness were prepared by tuning their cross-linking densities and reactant contents. <i>In vivo</i> studies of these nanogels show that softer nanogels pass through physiological barriers, especially the splenic filtration, more easily than their stiffer counterparts, consequently leading to longer circulation half-life and lower splenic accumulation. Results from this work emphasize the role of stiffness in designing long-circulating nanoparticles

Polycation‑<i>b</i>-Polyzwitterion Copolymer Grafted Luminescent Carbon Dots As a Multifunctional Platform for Serum-Resistant Gene Delivery and Bioimaging

Nanomaterials that integrate functions of imaging and gene delivery have been of great interest due to their potential use in simultaneous diagnosis and therapy. Herein, polycation-<i>b</i>-polysulfobetaine block copolymer, poly­[2-(dimethylamino) ethyl methacrylate]-<i>b</i>-poly­[<i>N</i>-(3-(methacryloylamino) propyl)-<i>N</i>,<i>N</i>-dimethyl-<i>N</i>-(3-sulfopropyl) ammonium hydroxide] (PDMAEMA-<i>b</i>-PMPDSAH) grafted luminescent carbon dots (CDs) were prepared via surface-initiated atom transfer radical polymerization (ATRP) and investigated as a multifunctional gene delivery system (denoted as CD-PDMA-PMPD) in which the CD cores acted as good multicolor cell imaging probes, the cationic PDMAEMA acted as a DNA condensing agent, and the outer shell of zwitterionic PMPDSAH block protected the vector against nonspecific interactions with serum components. As revealed by the fluorescent spectrum study, the photoluminescent attributes, especially the tunable emission property, were well inherited from the parent CDs. The CD-PDMA-PMPD could condense plasmid DNA into nanospheres with sizes of approximate 50 nm at a proper complex ratio, posing little cytotoxicity at higher ratios. It was shown that the hybrid vector exhibited significantly suppressed BSA protein adsorption and superior hemocompatibility compared to those of the widely used PEI25k. In the in vitro transfection assay, an increased serum concentration from 10 to 50% caused a dramatic drop in PEI25k transfection performance, whereas the transfection efficiency of CD-PDMA-PMPD was well maintained; CD-PDMA80-PMPD40 showed 13 and 28 times higher transfection efficiencies than PEI25k at 30 and 50% serum concentration, respectively. Intriguingly, the carbon dots in the transfected cells displayed excitation-dependent fluorescent emissions, portending that this polycation-polyzwitterion modified CD will be a promising theranostic vector with excellent stealth performance

Sea Cucumber-Inspired Autolytic Hydrogels Exhibiting Tunable High Mechanical Performances, Repairability, and Reusability

Inspired by stimuli-responsive remarkable changes in consistency (hardening, softening, autolysis) of sea cucumbers, we synthesized a supramolecular polymer­(SP) hydrogel directly by photoinitiated aqueous polymerization of <i>N</i>-acryloyl 2-glycine monomer bearing one amide and one carboxyl group on the side chain. The SP hydrogels doped with Ca²⁺ demonstrated excellent mechanical properties–high tensile strength (∼1.3 MPa), large stretchability (up to 2300%), high compressive strength (∼10.8 MPa), and good toughness (∼1000 J m^–2) due to cooperative hydrogen bonding interactions from amide and carboxyl together with Ca²⁺ cross-linking. Responding to the change in pH and Ca²⁺ concentration, the hydrogels could modulate their network stability and mechanical properties: at pH3.0 and higher Ca²⁺ content, the hydrogel formed low swelling network which was stiff and stable; in alkaline or neutral buffer with lower content of or without Ca²⁺, the hydrogel formed a highly swollen transient network, which was soft and eventually autolyzed. The reversible multiple noncovalent bonds enabled the hydrogels to achieve thermoplasticity, self-healability, and reusability. Notably, distinct formulations of hydrogels could be welded together under heating to form a gradient hydrogel. In vitro cytotoxicity assay and subcutaneous implantation indicated that the SP hydrogels were biocompatible and autolytic in vivo. The SP hydrogels may find applications as temporary biodevices for intestinal drug delivery or for injectable filling in assisting suturing small vessels

The role of the <i>SDF-1</i>-<i>CXCR4</i> pathway in the homing of MSCs.

<p>(<b>A</b>) Kidney uptake of eGFP-labeled MSCs was measured by fluorescence microscopy 48 h after systemic administration (a: MSCs<i>^CXCR4</i>^/GFP, b: MSCs^GFP, c: MSCs^{sh<i>CXCR4</i>/GFP}). Labeled cells were detected surrounding the glomerulus (arrows). (<b>B and C</b>) Chemotaxis into transplanted kidneys was measured by RT-PCR andWestern blot. Recipients treated with MSCs^GFP were used as control. ★P<0.05 vs. control. (<b>D</b>) The expression of eGFP in different organs from recipient rats was measured 48 h after infusion.</p

Regulation of <i>CXCR4</i> expression affects the proliferation of MSCs in vitro.

<p>(<b>A</b>) Viability was decreased in MSCs^{sh<i>CXCR4</i>/GFP} and increased in MSCs<i>^CXCR4</i>^/GFP compared to MSCs^GFP or MSCs^native (control), as measured by the MTT assay (Mean ± SD; n = 6; P<0.05 from NO. 4 to 5 time point). (<b>B</b>) All cell nuclei exhibited blue fluorescent Hoechst 33342 staining, and EdU labeling indicated replicating cells. In MSCs<i>^CXCR4</i>, an increased number of cells exhibited red fluorescent EdU labeling following <i>CXCR4</i> overexpression. In MSCs^{sh<i>CXCR4</i>/GFP}, fewer cells exhibited red fluorescence, indicating that EdU labeling decreased with <i>CXCR4</i> knockdown. (<b>C</b>) The percentages of red fluorescent cells for different MSC groups are indicated in the histogram. There were more replicating cells for MSCs<i>^CXCR4</i>^/GFP than the control group. ★P<0.05 vs. control, and ▵P<0.01 vs. MSCs^{sh<i>CXCR4</i>/GFP}.</p

Characterization of rat bone marrow MSCs (α-MEM).

<p>(<b>A</b>) Isolated MSCs were round and small at 2 days after isolation. (<b>B</b>) After three passages, MSCs became larger and multiangular. (<b>C</b>) Before use, MSCs were mostly found in the clostridial form. (<b>D, E, F, G</b>) Fluorescent immunocytostaining showed that cultivated cells expressed CD29, strongly expressed CD105 and did not express CD14 and CD45. (<b>H</b>) Osteocyte lineage differentiation potential was determined by Alizarin Red S staining. (<b>I</b>) Oil Red O staining indicated the accumulation of oil droplets in cells that differentiated to adipocytes.</p

High Strength Multifunctional Multiwalled Hydrogel Tubes: Ion-Triggered Shape Memory, Antibacterial, and Anti-inflammatory Efficacies

In this study, ion-responsive hydrogen bonding strengthened hydrogels (termed as PVV) were synthesized by one-pot copolymerization of 2-vinyl-4,6-diamino-1,3,5-triazine (VDT), 1-vinylimidazole (VI), and polyethylene glycol diacrylate. The diaminotriazine–diaminotriazine (DAT–DAT) H-bonding interaction and copolymerization of VI contributed to a notable increase in comprehensive performances including tensile/compressive strength, elasticity, modulus, and fracture energy. In addition, introducing mM levels of zinc ions could further increase the mechanical properties of PVV hydrogels and fix a variety of temporary shapes due to the strong coordination of zinc with imidazole. The release of zinc ions from the hydrogel contributed to an antibacterial effect, without compromising the shape memory effect. Remarkably, a multiwalled hydrogel tube (MWHT) fixed with Zn²⁺ demonstrated much higher flexural strengths and a more sustainable release of zinc ions than the solid hydrogel cylinder (SHC). A Zn²⁺-fixed MWHT was implanted subcutaneously in rats, and it was found that the Zn²⁺-fixed MWHT exhibited anti-inflammatory and wound healing efficacies. The reported high strength hydrogel with integrated functions holds potential as a tissue engineering scaffold

Transplantation of MSCs was renoprotective.

<p>The effects of the <i>SDF-1</i>-<i>CXCR4</i> pathway on the therapeutic efficacy of MSCs for the treatment of injury in transplanted kidneys was evaluated by measuring serum urea, serum creatinine, pathology scores, and immunohistochemisty staining. BUN and Scr levels were measured in recipients that received MSCs or PBS 12 h and 72 h after the surgery. There were no difference between each group 12 h after the surgery (<b>A and B</b>), but there were significant diversity 72 h after the surgery (<b>C and D</b>). ★P<0.05 vs. MSCs^CXCR4/GFP; ▵P<0.05 vs. PBS. (<b>E</b>) HSK in transplanted kidneys that received different MSCs or PBS were calculated 72 h after the surgery (n = 8 per group). ★P<0.05 vs.MSCs<i>^CXCR4</i>^/GFP ; ▵P<0.05 vs. PBS. (<b>F</b>) Expression of CD25, FOXP3, or CD45 in the renal interstitium of native renal tissues or at different MSCs-treated groups after renal transplantation by immunohistochemistry. a, b, c: Paraffin-embedded sections of normal renal tissues showing weaker expression of CD25, or FOXP3, or CD45 [diaminobenzidine (DAB), original magnification 200×]. P<0.05 vs. transplanted kidney. d∼p: Paraffin-embedded sections of transplanted kidney exhibiting positive expression of CD25, or FOXP3, or CD45 in the renal interstitium (DAB, original magnification 200×). The expression of CD45,CD25 and FOXP3 were hyper in MSCs<i>^CXCR4</i>^/GFP-treated group.★ P<0.05 vs. MSCs<i>^CXCR4</i>^/GFP-treated group. ▵P<0.05 vs. PBS-treated group. Scale bars represent 50 µm.</p

Injury in transplanted organs.

<p>(<b>A, B</b>) Morphology analysis showed apparent injury in transplanted organs. (<b>C</b>) <i>SDF-1</i> protein was up-regulated in transplanted kidneys. The kidney tissue lysates from recipient rats were analyzed by ELISA to determine <i>SDF-1</i> protein expression at 5 time points after transplant surgery. The histogram indicates that <i>SDF-1</i> expression was up-regulated in transplanted kidneys at different time points post-surgery time. ★P<0.05 vs. normal kidney. (<b>D</b>) Pathology score analysis showed a disparity. Normal kidneys were used as controls (methods not shown). ★P<0.05 vs. control.</p

Antibody-based protein array system.

<p>Positive controls are located in the upper left-hand corner (four spots) and lower right-hand corner (two spots) of each membrane. (<b>A</b>) MSCs<i>^CXCR4</i>^/GFP. (<b>B</b>) MSCs<i>^shCXCR4</i>^/GFP. (<b>C</b>) MSCs^GFP. (<b>D</b>) MSCs^native. Down-regulated or up-regulated proteins are indicated with arrowheads. Histogram shows protein array results. (<b>E</b>) down-regulated proteins. (<b>F</b>) up-regulated proteins. ★P<0.05 vs. MSCs^GFP.</p