Fabrication of ß-CoV3O8 nanorods embedded in graphene sheets and their application for electrochemical charge storage electrode.

The fabrication of ß-CoV3O8 nanorods embedded in graphene sheets and their application as electrochemical charge storage electrodes is reported. From the surfactant treatment of raw graphite, graphene was directly prepared and its nanocomposite with ß-CoV3O8 nanorods distributed between graphene layers (ß-CoV3O8-G) was synthesized by a hydrothermal method. When applied as an anode in lithium-ion batteries, the ß-CoV3O8-G anode exhibits greatly improved charge and discharge capacities of 790 and 627 mAh · g-1, respectively, with unexpectedly high initial efficiency of 82%. The observed discharge capacity reflected that at least 3.7 mol of Li+ is selectively accumulated within the ß-CoV3O8 phase (LixCoV3O8, x > 3.7), indicative of significantly improved Li+ uptake when compared with aggregated ß-CoV3O8 nanorods. Moreover, very distinct peak plateaus and greatly advanced cycling performance are observed, showing more improved Li+ storage within the ß-CoV3O8 phase. As a supercapacitor electrode, moreover, our composite electrode exhibits very high peak pseudocapacitances of 2.71 F · cm-2 and 433.65 F · g-1 in the ß-CoV3O8 phase with extremely stable cycling performance. This remarkably enhanced performance in the individual electrochemical charge storage electrodes is attributed to the novel phase formation of ß-CoV3O8 and its optimized nanocomposite structure with graphene, which yield fast electrical conduction through graphene, easy accessibility of ions through the open multilayer nanosheet structure, and a relaxation space between the ß-CoV3O8-G.

Degrees of Inflammation in the Treatment of Subglottic Stenosis in a Rabbit Model: Histopathological Assessment of a Novel Bioabsorbable Ultra-high Ductility Magnesium Alloy Stent.

OBJECTIVE: Utilizing a novel histopathological scoring system and subglottic stenosis (SGS) rabbit model, we aimed to compare degrees of inflammation and severity of narrowing in the subglottis between two minimally invasive therapeutic modalities: endoscopic balloon dilation (EBD) alone versus EBD with placement of a bioabsorbable ultra-high ductility magnesium (UHD-Mg) alloy stent. METHODS: SGS was induced endoscopically via microsuspension laryngoscopy in 23 New Zealand white rabbits. The control group (n = 11) underwent EBD alone, the study arm (n = 12) underwent EBD with implantation of bioabsorbable UHD-Mg alloy stents. Rabbits were euthanized at 2-, 3-, and 6-weeks after SGS induction, coinciding with wound healing stages. Using Optical Coherence Tomography (OCT), cross-sectional areas of airways were compared to calculate the mean percentage of intraluminal area at sequential time points. A novel histopathological scoring system was used to analyze frozen sections of laryngotracheal complexes. The degree of inflammation was quantified by scoring changes in inflammatory cell infiltration, epithelial ulceration/metaplasia, subepithelial edema/fibrosis, and capillary number/dilation. Univariate analysis was utilized to analyze these markers. RESULTS: We found rabbits implanted with the bioabsorbable UHD-Mg alloy stent had statistically significantly higher scores in categories of hyperplastic change (stents vs controls: 1.48 vs 0.46 p < 0.001), squamous metaplasia (22 vs 5 p < 0.001), and neutrophils/fibrin in lumen (31 vs 8, p < 0.001). Rabbits who received EBD alone had higher scores of subepithelial edema and fibrosis (2.70 vs 3.49, p < 0.0256). The stented rabbits demonstrated significantly increased mean percent stenosis by intraluminal mean area compared to controls at 2 weeks (88.56 vs 58.98, p = 0.032), however at all other time points there was no significant difference between intraluminal subglottic stenosis by mean percent stenosis area. DISCUSSION: Rabbits with SGS treated with UHD-Mg alloy stents demonstrated histopathologic findings suggestive of lower levels of tracheal fibrosis. This could indicate a reduced tendency towards the development of stenosis when compared to EBD alone. There was not a difference in luminal size between stent and non-stented rabbits at the six-week end point. Histologically, however, overall the use of bioabsorbable UHD-Mg alloy stenting elicited a greater tissue response at the level of the superficial mucosa rather than fibrosis of the lamina propria seen in the stented rabbits. This suggests more favorable healing and less of a tendency towards fibrosis and stenosis even though there may not be a benefit from a luminal size standpoint during this early healing period. Compared to known complications of currently available non-bioabsorbable metal or silicone-based stents, this proof-of-concept investigation highlights the potential use of a novel biodegradable UHD-Mg stent as a therapeutic modality for pediatric SGS.

Biodegradable poly(lactide-co-glycolide) coatings on magnesium alloys for orthopedic applications.

Polymeric film coatings were applied by dip coating on two magnesium alloy systems, AZ31 and Mg4Y, in an attempt to slow the degradation of these alloys under in vitro conditions. Poly(lactic-co-glycolic acid) polymer in solution was explored at various concentrations, yielding coatings of varying thicknesses on the alloy substrates. Electrochemical corrosion studies indicate that the coatings initially provide some corrosion protection. Degradation studies showed reduced degradation over 3 days, but beyond this time point however, do not maintain a reduction in corrosion rate. Scanning electron microscopy indicates inhomogeneous coating durability, with gas pocket formation in the polymer coating, resulting in eventual detachment from the alloy surface. In vitro studies of cell viability utilizing mouse osteoblast cells showed improved biocompatibility of polymer coated substrates over the bare AZ31 and Mg4Y substrates. Results demonstrate that while challenges remain for long term degradation control, the developed polymeric coatings nevertheless provide short term corrosion protection and improved biocompatibility of magnesium alloys for possible use in orthopedic applications.

Bioactive Synthetic Polymer-Based Polyelectrolyte LbL Coating Assembly on Surface Treated AZ31-Mg Alloys.

Polyelectrolyte layer-by-layer (LbL) films on pretreated Mg containing 3 wt.% Al and 1 wt.% Zn (MgAZ31) alloy surfaces were prepared under physiological conditions offering improved bioresponse and corrosive protection. Pretreatments of the model MgAZ31 substrate surfaces were performed by alkaline and fluoride coating methods. The anti-corrosion and cytocompatibility behavior of pretreated substrates were evaluated. The LbL film assembly consisted of an initial layer of polyethyleneimine (PEI), followed by alternate layers of poly (lactic-co-glycolic acid) (PLGA) and poly (allylamine hydrochloride) (PAH), which self-arrange via electrostatic interactions on the pretreated MgAZ31 alloy substrate surface. The physicochemical characterization, surface morphologies, and microstructures of the LbL films were investigated using Fourier-transformed infrared spectroscopy (FTIR), atomic force microscopy (AFM), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The in vitro stability studies related to the LbL coatings confirmed that the surface treatments are imperative to achieve the lasting stability of PLGA/PAH layers. Electrochemical impedance spectroscopy measurements demonstrated that pretreated and LbL multilayered coated substrates enhanced the corrosion resistance of the bare MgAZ31 alloy. Cytocompatibility studies using human mesenchymal stem cells seeded directly over the substrates showed that the pretreated and LbL-generated surfaces were more cytocompatible, displaying reduced cytotoxicity than the bare MgAZ31. The release of bovine serum albumin protein from the LbL films was also studied. The initial data presented cooperatively demonstrate the promise of creating LbL layers on Mg-related bioresorbable scaffolds to obtain improved surface bio-related activity.

3D printing of drug-eluting bioactive multifunctional coatings for orthopedic applications.

Three-dimensional (3D) printing is implemented for surface modification of titanium alloy substrates with multilayered biofunctional polymeric coatings. Poly(lactic-co-glycolic) acid (PLGA) and polycaprolactone (PCL) polymers were embedded with amorphous calcium phosphate (ACP) and vancomycin (VA) therapeutic agents to promote osseointegration and antibacterial activity, respectively. PCL coatings revealed a uniform deposition pattern of the ACP-laden formulation and enhanced cell adhesion on the titanium alloy substrates as compared to the PLGA coatings. Scanning electron microscopy and Fourier-transform infrared spectroscopy confirmed a nanocomposite structure of ACP particles showing strong binding with the polymers. Cell viability data showed comparable MC3T3 osteoblast proliferation on polymeric coatings as equivalent to positive controls. In vitro live/dead assessment indicated higher cell attachments for 10 layers (burst release of ACP) as compared to 20 layers (steady release) for PCL coatings. The PCL coatings loaded with the antibacterial drug VA displayed a tunable release kinetics profile based on the multilayered design and drug content of the coatings. Moreover, the concentration of active VA released from the coatings was above the minimum inhibitory concentration and minimum bactericidal concentration, demonstrating its effectiveness against Staphylococcus aureus bacterial strain. This research provides a basis for developing antibacterial biocompatible coatings to promote osseointegration of orthopedic implants.

Expression of phosphophoryn is sufficient for the induction of matrix mineralization by mammalian cells.

Mineralized tissues such as dentin and bone assemble extracellular matrices uniquely rich in a variety of acidic phosphoproteins. Although these proteins are presumed to play a role in the process of biomineralization, key questions regarding the nature of their contributions remain unanswered. First, it is not known whether highly phosphorylated proteins alone can induce matrix mineralization, or whether this activity requires the involvement of other bone/dentin non-collagenous proteins. Second, it remains to be established whether the protein kinases that phosphorylate these acidic proteins are unique to cells responsible for producing mineralized tissues. To begin to address these questions, we consider the case of phosphophoryn (PP), due to its high content of phosphate, high affinity for Ca(2+), and its potential role in hydroxyapatite nucleation. We have created a model system of biomineralization in a cellular environment by expressing PP in NIH3T3 fibroblasts (which do not produce a mineralized matrix); as a positive control, PP was expressed in MC3T3-E1 osteoblastic cells, which normally mineralize their matrices. We show that expression of PP in NIH3T3 cells is sufficient for the induction of matrix mineralization. In addition, assessment of the phosphorylation status of PP in these cells reveals that the transfected NIH3T3 cells are able to phosphorylate PP. We suggest that the phosphorylation of PP is essential for mineral formation. The principle goal of this study is to enrich the current knowledge of mineralized tissue phosphorylation events by analyzing them in the context of a complete cellular environment.

Effect of Lithium and Aluminum on the Mechanical Properties, In Vivo and In Vitro Degradation, and Toxicity of Multiphase Ultrahigh Ductility Mg-Li-Al-Zn Quaternary Alloys for Vascular Stent Application.

Magnesium alloys are the most widely studied biodegradable metals for biodegradable vascular stent application. Two major issues with current magnesium alloy based stents are their low ductility and fast corrosion rates. Several studies have validated that introduction of Li into the magnesium alloys will significantly improve the ductility while alloying with Al will improve the corrosion resistance and strength. In the present study, we studied the effects of alloying different amounts of Li and Al on the Mg-Li-Al-Zn (LAZ) quaternary alloy system. Rods were made from four different LAZ alloys, namely, LAZ611, LAZ631, LAZ911, and LAZ931 following melting, casting, and then extrusion. Systematic assessment of mechanical properties, in vitro corrosion, cytotoxicity, and in vivo degradation including local and systemic toxicity conducted demonstrated the beneficial effects of Li and Al on the mechanical properties. Our results specifically suggest that alloying with Li significantly improved the ductility while Al enhanced the strength of the LAZ alloys. Four of the LAZ alloys exhibited different corrosion rates in Hank's balanced salt solution depending on the chemical composition. Indirect in vitro cytotoxicity tests also showed lower cytotoxicity for the alloys exhibiting higher corrosion resistance. In vivo corrosion rates in the mouse subcutaneous model showed different corrosion rates compared to the in vitro tests. Nevertheless, all of the four LAZ alloys displayed no local and systemic toxicity based on the histology analysis. This research study, therefore, demonstrated the benefits of using Li and Al as alloying elements in LAZ alloys and the potential use of LAZ alloys for vascular stent application.

In-vivo efficacy of biodegradable ultrahigh ductility Mg-Li-Zn alloy tracheal stents for pediatric airway obstruction.

Pediatric laryngotracheal stenosis is a complex congenital or acquired airway injury that may manifest into a potentially life-threatening airway emergency condition. Depending on the severity of obstruction, treatment often requires a combination of endoscopic techniques, open surgical repair, intraluminal stenting, or tracheostomy. A balloon expandable biodegradable airway stent maintaining patency while safely degrading over time may address the complications and morbidity issues of existing treatments providing a less invasive and more effective management technique. Previous studies have focused on implementation of degradable polymeric scaffolds associated with potentially life-threatening pitfalls. The feasibility of an ultra-high ductility magnesium-alloy based biodegradable airway stents was demonstrated for the first time. The stents were highly corrosion resistant under in vitro flow environments, while safely degrading in vivo without affecting growth of the rabbit airway. The metallic matrix and degradation products were well tolerated by the airway tissue without exhibiting any noticeable local or systemic toxicity.

Subglottic Stenosis: Development of a Clinically Relevant Endoscopic Animal Model.

OBJECTIVE: Develop a clinically relevant and reproducible endoscopic animal model for subglottic stenosis amenable to testing of minimally invasive therapeutic modalities. STUDY DESIGN: Cohort study. SETTING: Division of Laboratory Animals Research, University of Pittsburgh. SUBJECTS AND METHODS: Subglottic stenosis was induced endoscopically via microsuspension laryngoscopy in 26 New Zealand white rabbits. A trimmed polypropylene brush connected to a novel electronic stenosis induction apparatus was used to create circumferential trauma to the subglottis. By using open source image analysis software, the cross-sectional areas of the stenotic and native airways were compared to calculate the percentage of stenosis and the Myer-Cotton classification grade. RESULTS: Of the 26 rabbits, 24 (92%) exhibited stenosis after the first attempt. The mean percentage of airway stenosis was 57% (range, 34%-85%; SD, 15%). Five rabbits (19.2%) died on the day of stenosis induction from procedural complications. Of the 21 rabbits, 2 demonstrated no stenosis 7 days after initial injury and so underwent reinduction of airway injury, upon which they developed stenosis. Overall, 14 of the 21 rabbits (67%) exhibited moderate to severe stenosis (grade 2 or 3). CONCLUSION: The stenosis induction apparatus reliably induced stenosis with a low mortality rate as compared with that of other methods in the literature. The device could be improved to generate a predetermined potentially reproducible grade of stenosis as desired by the operator. This method sets the stage for a clinically relevant and reproducible subglottic stenosis disease model that is amenable to testing of minimally invasive treatment modalities.

A Novel Sulforaphane-Regulated Gene Network in Suppression of Breast Cancer-Induced Osteolytic Bone Resorption.

Bone is the most preferred site for colonization of metastatic breast cancer cells for each subtype of the disease. The standard of therapeutic care for breast cancer patients with bone metastasis includes bisphosphonates (e.g., zoledronic acid), which have poor oral bioavailability, and a humanized antibody (denosumab). However, these therapies are palliative, and a subset of patients still develop new bone lesions and/or experience serious adverse effects. Therefore, a safe and orally bioavailable intervention for therapy of osteolytic bone resorption is still a clinically unmet need. This study demonstrates suppression of breast cancer-induced bone resorption by a small molecule (sulforaphane, SFN) that is safe clinically and orally bioavailable. In vitro osteoclast differentiation was inhibited in a dose-dependent manner upon addition of conditioned media from SFN-treated breast cancer cells representative of different subtypes. Targeted microarrays coupled with interrogation of The Cancer Genome Atlas data set revealed a novel SFN-regulated gene signature involving cross-regulation of runt-related transcription factor 2 (RUNX2) and nuclear factor-κB and their downstream effectors. Both RUNX2 and p65/p50 expression were higher in human breast cancer tissues compared with normal mammary tissues. RUNX2 was recruited at the promotor of NFKB1 Inhibition of osteoclast differentiation by SFN was augmented by doxycycline-inducible stable knockdown of RUNX2. Oral SFN administration significantly increased the percentage of bone volume/total volume of affected bones in the intracardiac MDA-MB-231-Luc model indicating in vivo suppression of osteolytic bone resorption by SFN. These results indicate that SFN is a novel inhibitor of breast cancer-induced osteolytic bone resorption in vitro and in vivo.

Nanostructured silicon anodes for lithium ion rechargeable batteries.

Rechargeable lithium ion batteries are integral to today's information-rich, mobile society. Currently they are one of the most popular types of battery used in portable electronics because of their high energy density and flexible design. Despite their increasing use at the present time, there is great continued commercial interest in developing new and improved electrode materials for lithium ion batteries that would lead to dramatically higher energy capacity and longer cycle life. Silicon is one of the most promising anode materials because it has the highest known theoretical charge capacity and is the second most abundant element on earth. However, silicon anodes have limited applications because of the huge volume change associated with the insertion and extraction of lithium. This causes cracking and pulverization of the anode, which leads to a loss of electrical contact and eventual fading of capacity. Nanostructured silicon anodes, as compared to the previously tested silicon film anodes, can help overcome the above issues. As arrays of silicon nanowires or nanorods, which help accommodate the volume changes, or as nanoscale compliant layers, which increase the stress resilience of silicon films, nanoengineered silicon anodes show potential to enable a new generation of lithium ion batteries with significantly higher reversible charge capacity and longer cycle life.

Cell derived hierarchical assembly of a novel phosphophoryn-based biomaterial.

Phosphophoryn (PP) is an acidic phosphoprotein belonging to the small integrin-bindingligand N-linked glycoprotein (SIBLING) protein family. PP is highly phosphorylated with approximately 200 phosphates per molecule and has a high affinity for calcium. The aim of this manuscript is to demonstrate that PP has the ability to self-assemble when it is overexpressed in a mammalian cell in the presence of calcium. Our data show that when PP is overexpressed using an adenovirus, the self-assembly occurs in the endoplasmic reticulum (ER) which contains high calcium concentration. We hypothesize that the physicochemical properties of the highly phosphorylated state and acidic nature of PP are playing an important role in its assembly in the ER. It appears that when a critical concentration of PP is reached, the assembly is then favored and facilitated. This self-assembly could be due to several factors. (1) The ER provides an ideal environment for this phenomenon to occur, since the ER environment usually promotes aggregation [Stevens and Argon: Semin Cell Dev Biol 1999;10:443-454]. (2) In addition to PP's physicochemical properties, the unfolded protein response could also be playing a role in this self-assembly [Schroder and Kaufman: Mutat Res 2005;569:29-63]. Unfolded protein response could be activated by a broad spectrum of insults that result in protein misfolding and ultimately blocking of the protein synthesis progression to the Golgi apparatus resulting in an accumulation of the protein in the ER. In summary, our data show that PP has the ability to self-assemble in a hierarchical manner.

Evaluation of magnesium alloys for use as an intraluminal tracheal for pediatric applications in a rat tracheal bypass model.

Tracheal stenting currently using non-degradable stents is commonplace for treatment of trauma, prolonged intubation related adult airway obstructions, and pediatric patients-associated tracheal stenosis conditions. Degradable tracheal stent placement will avoid complications of stent removal and restenosis. Widespread reports exist on degradable magnesium alloys success for orthopedic and cardiovascular applications but none to date for intra tracheal use. This research explores the use of pure Mg, AZ31, and Mg-3Y alloys for degradable tracheal stent assessment. In vitro evaluation of magnesium, prototype stents in a bioreactor simulate the airway environment and corrosion. Micro-CT imaging and biocompatibility evaluation helped assess the 24-week degradation of intraluminal alloy stents following implantation in a rat tracheal in vivo bypass model. Histological analysis indicate tissue response of the harvested stented trachea segments after each time point. Corrosion studies for each alloy indicate significant differences between the simulated and control in vitro conditions. AZ31 exhibited the lowest volume loss of 6.8% in saline, while pure Mg displayed the lowest volume loss of 4.6% in simulated airway fluid (SAF), both at 1-week time points. Significant differences in percentage of total volume lost after 6 months were determined between the alloys over time. MgY alloy displayed the slowest corrosion losing only 15.1% volume after 24 weeks of immersion. Additionally, in vitro magnesium alloy corrosion was not significantly different from the percentage of total volume lost in vivo at 1-week time point. The study demonstrates promise of magnesium alloys for intraluminal tracheal stent application albeit viability of a clinically translatable model warrants further studies. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1844-1853, 2019.

Corrosion and bone healing of Mg-Y-Zn-Zr-Ca alloy implants: Comparative in vivo study in a non-immobilized rat femoral fracture model.

Biodegradable magnesium (Mg) alloys exhibit improved mechanical properties compared to degradable polymers while degrading in vivo circumventing the complications of permanent metals, obviating the need for surgical removal. This study investigated the safety and efficacy of Mg-Y-Zn-Zr-Ca (WZ42) alloy compared to non-degradable Ti6Al4V over a 14-week follow-up implanted as pins to fix a full osteotomy in rat femurs and as wires wrapped around the outside of the femurs as a cerclage. We used a fully load bearing model allowing implants to intentionally experience realistic loads without immobilization. To assess systemic toxicity, blood cell count and serum biochemical tests were performed. Livers and kidneys were harvested to observe any accumulation of alloying elements. Hard and soft tissues adjacent to the fracture site were also histologically examined. Degradation behavior and bone morphology were determined using micro-computed tomography scans. Corrosion occurred gradually, with degradation seen after two weeks of implantation with points of high stress observed near the fracture site ultimately resulting in WZ42 alloy pin fracture. At 14 weeks however, normal bone healing was observed in femurs fixed with the WZ42 alloy confirmed by the presence of osteoid, osteoblast activity, and new bone formation. Blood testing exhibited no significant changes arising from the WZ42 alloy compared to the two control groups. No recognizable differences in the morphology and more importantly, no accumulation of Mg, Zn, and Ca in the kidney and liver of rats were observed. These load bearing model results collectively taken, thus demonstrate the feasibility for use of the Mg-Y-Zn-Zr-Ca alloy for long bone fracture fixation applications.

In Vitro Biodegradation and In Vivo Biocompatibility of Forsterite Bio-Ceramics: Effects of Strontium Substitution.

The present study investigates the potential use of forsterite as an orthopedic biomaterial along with the role of strontium oxide (SrO) as a dopant. The in vitro degradation behavior was measured as a function of immersion time in simulated body fluid (SBF) for up to 8 weeks and was analyzed by micro computed tomography (µ-CT) and scanning electron microscopy (SEM). All the doped samples showed higher degradation than pure sample. The in vitro cytocompatibility study showed good cytocompatibility and proliferation of MC3T3-E1 cells on Sr-doped MgS samples. The in vivo experiments were carried out by implanting the ceramics in a rabbit femur for 30 and 90 days. The 3D µ-CT and SEM images of 2 and 3 wt % Sr-doped MgS showed increased bone regeneration around the implant materials compared with pure and 1 wt % Sr-doped MgS, which was further confirmed by quantitative oxytetracycline labeling. The histological examination of three major organs of heart, kidney, and liver confirmed that the degradation product of the MgS ceramics, with or without doping, had no toxicological side effects. These results indicate that Sr-doped MgS bioceramics exhibit enhanced degradability with the potential to be used for temporary bone regeneration.

Cross-linked enzyme aggregates of alginate lyase: A systematic engineered approach to controlled degradation of alginate hydrogel.

An enzyme aggregate of alginate lyase (EC 4.2.2.3) from flavobactierium was prepared using ammonium sulfate. The resultant aggregates upon cross-linking with glutaraldehyde produced insoluble and catalytically active cross-linked enzyme aggregate (CLEA) enzyme. The catalytic activity and stability of the cross-linked enzyme aggregate of alginate lyase (CLEA-AL) was studied in the presence of various pH, temperatures and organic solvents. Reusability, storage stability and surface morphology of the CLEA-AL were also studied. The native enzyme and CLEA-AL exhibited maximum enzyme activity at pH of 6.3 and at a temperature of 40°C. The CLEA-AL has good stability in nonpolar organic solvents and is thermally stable up to 50°C over a period of 8h. By encapsulating CLEA-AL into alginate hydrogel, we demonstrate that alginate hydrogels can be enzymatically degraded in a controlled fashion. The results also showed that degradation of alginate hydrogel with CLEA-AL incorporated beads is slower than native enzyme and therefore, CLEA-AL can be used for controlled degradation and release of various biologics from the degrading gel.

In Vivo Biocompatibility of Zinc-Doped Magnesium Silicate Bio-Ceramics.

Magnesium-based bioceramics have emerged as a new class of biodegradable bone replacement material due to their higher degradation and good cytocompatibility. In the current research, we have prepared pure and zinc-doped magnesium silicate (MgS) bioceramics by solid state method and evaluated the in vitro degradability and in vivo biocompatibility. In vitro degradation of the MgS bioceramics was assessed in simulated body fluid (SBF) which showed enhanced degradability for 0.5 wt % Zn doped MgS samples. The in vivo biocompatibility was evaluated by implanting the samples in rabbit femur critical size defect. All the MgS samples were well-integrated at the host tissue site as evident in 90 day radiographic images and micro computed tomography (µ-CT). Oxytetracycline labeling indicated that 0.5 wt % Zn doped MgS samples had better bone regeneration after 90 days of implantation as compared to pure and 0.25 wt % Zn-doped samples. Any systemic and organ toxicity was negated by normal vital organ (heart, kidney, and liver) histology at 90 days.

Development of an Alginate Array Platform to Decouple the Effect of Multiparametric Perturbations on Human Pluripotent Stem Cells During Pancreatic Differentiation.

Human embryonic stem cells (hESC)-derived functional cells hold great promise for regenerative cell therapy. Currently approved strategies for clinical translation requires the isolation of the hESCs-derived cells in materials allowing transfer of reagents but preventing integration with the host. However, hESC fate is known to be sensitive to its local microenvironment, both chemical and physical. Given the complexity of hESC response to environmental parameters, it will be important to evaluate the cell response to multiple combinatorial perturbations. Such complex perturbations are best enabled by exploiting high-throughput screening platforms. In this study, the authors report the effect of multivariate perturbations on hESC differentiation, enabled by the development of high throughput 3D alginate array platform. Specifically, the sensitivity of hESC propagation and pancreatic differentiation to substrate properties and cell culture configuration is analyzed. Cellular response to array perturbations is analyzed by quantitative imaging, and cell sensitivity was determined through statistical modeling. The results indicate that configuration is the stronger determinant of hESC proliferation and differentiation, while substrate properties fine-tune the expression around the average levels. This platform allowed for multiparametric perturbations, and in combination with statistical modeling, allows to identify the sensitivity of hESC proliferation and fate to multiparametric modulation.

In Vitro and in Vivo Evaluation of Multiphase Ultrahigh Ductility Mg-Li-Zn Alloys for Cardiovascular Stent Application.

Magnesium alloys have been extensively studied as a novel biodegradable metallic material for cardiovascular stent application. However, the ductility limitation of magnesium alloy has been a key issue for biodegradable stents applications. In this study, two different multiphase ultrahigh ductility Mg-Li-Zn alloys, LZ61 and LZ91, are fabricated in the form of extruded rods and evaluated both in vitro and in vivo. The microstructure, mechanical properties and in vitro degradation are evaluated as well as in vitro cytotoxicity. The in vivo degradation, tissue response, and systematic toxicity are evaluated in a mouse subcutaneous model. Measurements show that LZ61 and LZ91 exhibit more than 40% elongation at fracture without significantly compromising the strength. Both in vitro and in vivo degradation showed low degradation rates for LZ61 but high degradation rate for the LZ91 alloy. Excellent biocompatibility is observed both in vivo and in vitro for LZ61 and LZ91. In summary, this study successfully demonstrates that the ultraductility multiphase Mg-Li-Zn alloy has the potential to be used for stent applications. Compared to LZ91, the LZ61 alloy shows better balance of mechanical properties, corrosion resistance, and biocompatibility, indicating its promise for cardiovascular stent applications.

3D heterogeneous islet organoid generation from human embryonic stem cells using a novel engineered hydrogel platform.

Organoids, which exhibit spontaneous organ specific organization, function, and multi-cellular complexity, are in essence the in vitro reproduction of specific in vivo organ systems. Recent work has demonstrated human pluripotent stem cells (hPSCs) as a viable regenerative cell source for tissue-specific organoid engineering. This is especially relevant for engineering islet organoids, due to the recent advances in generating functional beta-like cells from human pluripotent stem cells. In this study, we report specific engineering of regenerative islet organoids of precise size and cellular heterogeneity, using a novel hydrogel system, Amikagel. Amikagel facilitated controlled and spontaneous aggregation of human embryonic stem cell derived pancreatic progenitor cells (hESC-PP) into robust homogeneous spheroids. This platform further allowed fine control over the integration of multiple cell populations to produce heterogeneous spheroids, which is a necessity for complex organoid engineering. Amikagel induced hESC-PP spheroid formation enhanced pancreatic islet-specific Pdx-1 and NKX6.1 gene and protein expression, while also increasing the percentage of committed population. hESC-PP spheroids were further induced towards mature beta-like cells which demonstrated increased Beta-cell specific INS1 gene and C-peptide protein expression along with functional insulin production in response to in vitro glucose challenge. Further integration of hESC-PP with biologically relevant supporting endothelial cells resulted in multicellular organoids which demonstrated spontaneous maturation towards islet-specific INS1 gene and C-peptide protein expression along with a significantly developed extracellular matrix support system. These findings establish Amikagel -facilitated platform ideal for islet organoid engineering.