Selective targeting of microglia by quantum dots

Background

Microglia, the resident immune cells of the brain, have been implicated in brain injury and various neurological disorders. However, their precise roles in different pathophysiological situations remain enigmatic and may range from detrimental to protective. Targeting the delivery of biologically active compounds to microglia could help elucidate these roles and facilitate the therapeutic modulation of microglial functions in neurological diseases.

Methods

Here we employ primary cell cultures and stereotaxic injections into mouse brain to investigate the cell type specific localization of semiconductor quantum dots (QDs) in vitro and in vivo. Two potential receptors for QDs are identified using pharmacological inhibitors and neutralizing antibodies.

Results

In mixed primary cortical cultures, QDs were selectively taken up by microglia; this uptake was decreased by inhibitors of clathrin-dependent endocytosis, implicating the endosomal pathway as the major route of entry for QDs into microglia. Furthermore, inhibiting mannose receptors and macrophage scavenger receptors blocked the uptake of QDs by microglia, indicating that QD uptake occurs through microglia-specific receptor endocytosis. When injected into the brain, QDs were taken up primarily by microglia and with high efficiency. In primary cortical cultures, QDs conjugated to the toxin saporin depleted microglia in mixed primary cortical cultures, protecting neurons in these cultures against amyloid beta-induced neurotoxicity.

Conclusions

These findings demonstrate that QDs can be used to specifically label and modulate microglia in primary cortical cultures and in brain and may allow for the selective delivery of therapeutic agents to these cells.

Off-wafer fabrication and surface modification of asymmetric 3D SU-8 microparticles

This protocol details a method of fabricating off-wafer, multilayered, asymmetric microparticles from the epoxy-based photosensitive polymer SU-8. Also included are methods for altering the surface properties of SU-8 and introducing functional groups for further covalent coupling reactions. These techniques may be used to create microparticles for applications in drug delivery and tissue engineering. Microparticle design, fabrication and surface modification can be completed in 2 d.

Effects of pore size, implantation time, and nano-surface properties on rat skin ingrowth into percutaneous porous titanium implants

The main problem of percutaneous osseointegrated implants is poor skin-implant integration, which may cause infection. This study investigated the effects of pore size (Small, 40-100 μm and Large, 100-160 μm), nanotubular surface treatment (Nano), and duration of implantation (3 and 6 weeks) on skin ingrowth into porous titanium. Each implant type was percutaneously inserted in the back of 35 rats randomly assigned to seven groups. Implant extrusion rate was measured weekly and skin ingrowth into implants was determined histologically after harvesting implants. It was found that all three types of implants demonstrated skin tissue ingrowth of over 30% (at week 3) and 50% (at weeks 4-6) of total implant porous area under the skin; longer implantation resulted in greater skin ingrowth (p < 0.05). Only one case of infection was observed (infection rate 2.9%). Small and Nano groups showed the same implant extrusion rate which was lower than the Large group rate (0.06 ± 0.01 vs. 0.16 ± 0.02 cm/week; p < 0.05). Ingrowth area was comparable in the Small, Large, and Nano implants. However, qualitatively, the Nano implants showed greatest cellular inhabitation within first 3 weeks. We concluded that percutaneous porous titanium implants allow for skin integration with the potential for a safe seal.

Hemodynamic Performance and Thrombogenic Properties of a Superhydrophobic Bileaflet Mechanical Heart Valve

In this study, we explore how blood-material interactions and hemodynamics are impacted by rendering a clinical quality 25 mm St. Jude Medical Bileaflet mechanical heart valve (BMHV) superhydrophobic (SH) with the aim of reducing thrombo-embolic complications associated with BMHVs. Basic cell adhesion is evaluated to assess blood-material interactions, while hemodynamic performance is analyzed with and without the SH coating. Results show that a SH coating with a receding contact angle (CA) of 160° strikingly eliminates platelet and leukocyte adhesion to the surface. Alternatively, many platelets attach to and activate on pyrolytic carbon (receding CA = 47), the base material for BMHVs. We further show that the performance index increases by 2.5% for coated valve relative to an uncoated valve, with a maximum possible improved performance of 5%. Both valves exhibit instantaneous shear stress below 10 N/m² and Reynolds Shear Stress below 100 N/m². Therefore, a SH BMHV has the potential to relax the requirement for antiplatelet and anticoagulant drug regimens typically required for patients receiving MHVs by minimizing blood-material interactions, while having a minimal impact on hemodynamics. We show for the first time that SH-coated surfaces may be a promising direction to minimize thrombotic complications in complex devices such as heart valves.

Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

Resorbable bacterial cellulose membranes with strontium release for guided bone regeneration

Hybrid materials, based on bacterial cellulose (BC) and hydroxyapatite (HA), have been investigated for guided bone regeneration (GBR). However, for some GBR, degradability in the physiological environment is an essential requirement. The present study aimed to explore the use of oxidized bacterial cellulose (OxBC) membranes, associated with strontium apatite, for GBR applications. BC membranes were produced by fermentation and purified, before oxidizing and mineralizing by immersing in strontium chloride solution and sodium bibasic phosphate for 5 cycles. The hybrid materials (BC/HA/Sr, BC/SrAp, OxBC/HA/Sr and OxBC/SrAp) were characterized for biodegradability and bioactivity and for their physicochemical and morphological properties. In vitro cytotoxicity and hemolytic properties of the materials were also investigated. In vivo biocompatibility was analyzed by performing histopathological evaluation at 1, 3 and 9 weeks in mices. Results showed that the samples presented different strontium release profiles and that oxidation enhances degradation under physiological conditions. All the hybrid materials were bioactive. Cell viability assay indicated that the materials are non-cytotoxic and in vivo studies showed low inflammatory response and increased connective tissue repair, as well as degradation in most of the materials, especially the oxidized membranes. This study confirms the potential use of bacterial cellulose-derived hybrid membranes for GBR.

Cluster-based probability model and its application to image and texture processing

We develop, analyze, and apply a specific form of mixture modeling for density estimation within the context of image and texture processing. The technique captures much of the higher order, nonlinear statistical relationships present among vector elements by combining aspects of kernel estimation and cluster analysis. Experimental results are presented in the following applications: image restoration, image and texture compression, and texture classification.

Intraoperative serum lactate is not a predictor of survival after glioblastoma surgery

BACKGROUND

Cancer cells can produce lactate in high concentrations. Two previous studies examined the clinical relevance of serum lactate as a biomarker in patients with brain tumors. Patients with high-grade tumors have higher serum concentrations of lactate than those with low-grade tumors. We hypothesized that serum lactic could be used of biomarker to predictor of survival in patients with glioblastoma (GB).

METHODS

This was a retrospective study. Demographic, lactate concentrations and imaging data from 275 adult patients with primary GB was included in the analysis. The progression free survival (PFS) and overall survival (OS) rates were compared in patients who had above and below the median concentrations of lactate. We also investigated the correlation between lactate concentrations and tumor volume. Multivariate analyses were conducted to test the association lactate, tumor volume and demographic variables with PFS and OS.

RESULTS

The median serum concentration of lactate was 2.3mmol/L. A weak correlation was found between lactate concentrations and tumor volume. Kaplan-Meier curves demonstrated similar survival in patients with higher or lower than 2.3mmol/L of lactate. The multivariate analysis indicated that the intraoperative levels of lactate were not independently associated with changes in survival. On another hand, a preoperative T1 volume was an independent predictor PFS (HR 95%CI: 1.41, 1.02-1.82, p=0.006) and OS (HR 95%CI: 1.47, 1.11-1.96, p=0.006).

CONCLUSION

This retrospective study suggests that the serum concentrations of lactate cannot be used as a biomarker to predict survival after GB surgery. To date, there are no clinically available serum biomarkers to determine prognosis in patients with high-grade gliomas. These tumors may produce high levels of lactic acid. We hypothesized that serum lactic could be used of biomarker to predictor of survival in patients with glioblastoma (GB). In this study, we collected perioperative and survival data from 275 adult patients with primary high-grade gliomas to determine whether intraoperative serum acid lactic concentrations can serve as a marker of prognosis. The median serum concentration of lactate was 2.3mmol/L. Our analysis indicated the intraoperative levels of lactate were not independently associated with changes in survival. This retrospective study suggests that the serum concentrations of lactate cannot be used as a biomarker to predict survival after GB surgery.

Effects of calcium and phosphorus incorporation on the properties and bioactivity of TiO2 nanotubes

In this study, we investigate the formation of calcium and phosphorus-doped TiO₂ nanotubes, produced by potentiostatic anodization of Ti in viscous electrolyte-containing HF and Ca/P ions. Characterization of the produced oxide layer was conducted using scanning electron microscopy, glancing-angle X-ray diffraction, X-ray photoelectron spectroscopy, contact angle, and protein adsorption measurements. Adipose-derived stem cells were used to study material cytotoxicity, cell viability and proliferation, and cell morphology and growth. To evaluate the adipose-derived stem-cell differentiation, we investigated the expression of osteocalcin and osteopontin by cells as well as calcium mineralization. Results show that it was possible to produce a superhydrophilic titanium oxide nanotube layer with incorporation of Ca and P ions. The presence of Ca and P in the oxide layer not only improved the cell adhesion and proliferation but also stimulated the production of key marker proteins indicating differentiation of cells.

Pulmonary gas exchange during exercise in patients with chronic obliterative pulmonary hypertension

The effect of exercise on pulmonary gas exchange was investigated in 7 patients with pulmonary hypertension resulting from primary pulmonary hypertension or recurrent pulmonary emboli. During supine bicycle exercise averaging 2.4 times baseline O2 consumption there was a significant fall in the arterial PO2 (64 +/- 1.1 to 56 +/- 5.4) and widening of the alveolar-arterial gradient for O2 (50 +/- 4.6 to 62 +/- 5.5). Measurement of the distribution of ventilation-perfusion (VA/Q) ratios by the multiple inert gas technique demonstrated no increase in VA/Q inequality. The increased hypoxemia was due to the fall in the mixed venous PO2 and its impact on the end-capillary blood of the shunt and low VA/Q units present at both rest and exercise. A concomitant shift in the mean VA/Q ratio for the normal lung units mitigated but could not eliminate the fall in the arterial PO2. We conclude that the increased hypoxemia seen during exercise in these patients is due to the widened arterial-venous O2 difference expected with exercise and its effect on the mild VA/Q inequality characteristic of this disorder.

Recent Advances in Tissue-Engineered Cardiac Scaffolds-The Progress and Gap in Mimicking Native Myocardium Mechanical Behaviors

Heart failure is the leading cause of death in the US and worldwide. Despite modern therapy, challenges remain to rescue the damaged organ that contains cells with a very low proliferation rate after birth. Developments in tissue engineering and regeneration offer new tools to investigate the pathology of cardiac diseases and develop therapeutic strategies for heart failure patients. Tissue -engineered cardiac scaffolds should be designed to provide structural, biochemical, mechanical, and/or electrical properties similar to native myocardium tissues. This review primarily focuses on the mechanical behaviors of cardiac scaffolds and their significance in cardiac research. Specifically, we summarize the recent development of synthetic (including hydrogel) scaffolds that have achieved various types of mechanical behavior-nonlinear elasticity, anisotropy, and viscoelasticity-all of which are characteristic of the myocardium and heart valves. For each type of mechanical behavior, we review the current fabrication methods to enable the biomimetic mechanical behavior, the advantages and limitations of the existing scaffolds, and how the mechanical environment affects biological responses and/or treatment outcomes for cardiac diseases. Lastly, we discuss the remaining challenges in this field and suggestions for future directions to improve our understanding of mechanical control over cardiac function and inspire better regenerative therapies for myocardial restoration.

Mechanical properties of a hierarchical electrospun scaffold for ovine anterior cruciate ligament replacement

The anterior cruciate ligament (ACL) acts to stabilize the knee and prevent excessive motion of the tibia relative to the femur. Tears of the ACL are common and can result in pain and damage to surrounding tissues. Thus a torn ACL is often surgically replaced with an autograft or allograft material. Drawbacks to clinically available ACL grafts motivate the development of a tissue engineered ACL replacement. Our group has previously developed a polycaprolactone electrospun scaffold that mimics the hierarchical structure of the ACL. The goal of this study was to investigate the mechanical properties of the electrospun scaffold as an ACL replacement. Scaffold mechanical properties were assessed prior to implantation via stress relaxation and pull to failure testing. Following in vitro characterization, electrospun scaffolds and soft tissue grafts were implanted into ovine cadaver stifle joints as ACL replacements. Stifle joints with ACL replacements were tested via a simulated anterior drawer test as well as in situ stress relaxation and pull to failure tests and compared to stifle joints with the native ACL intact. Prior to implantation the scaffold matched the native ovine ACL well in the range of functional strains as evidenced by stress relaxation measures and the toe region stiffness. After implantation the scaffold was more similar to the native ACL than the soft tissue graft, particularly when it came to reducing joint laxity and matching stress relaxation measures. These results demonstrate that the electrospun scaffold has the potential to be a suitable material for ACL replacement. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:421-430, 2019.

Gentamicin-Releasing Titania Nanotube Surfaces Inhibit Bacteria and Support Adipose-Derived Stem Cell Growth in Cocultures

Infection is the second leading cause of failure of orthopedic implants following incomplete osseointegration. Materials that increase the antimicrobial properties of surfaces while maintaining the ability for bone cells to attach and proliferate could reduce the failure rates of orthopedic implants. In this study, titania nanotubes (Nts) were modified with chitosan/heparin polyelectrolyte multilayers (PEMs) for gentamicin delivery. The antimicrobial activity of the surfaces was tested by coculturing bacteria with mammalian cells. Over 60% of gentamicin remained on the surface after an initial burst release on the first day. Antimicrobial activity of these surfaces was determined by exposure to Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) for up to 24 h. Gentamicin surfaces had less live E. coli and S. aureus by 6 h and less E. coli by 24 h compared to Nt surfaces. S. aureus and human adipose-derived stem cells (hADSCs) were cocultured on surfaces for up to 7 days to characterize the so-called "race to the surface" between bacteria and mammalian cells, which is hypothesized to ultimately determine the outcome of orthopedic implants. By day 7, there was no significant difference in bacteria between surfaces with gentamicin adsorbed on the surface and surfaces with gentamicin in solution. However, gentamicin delivered in solution is toxic to hADSCs. Alternatively, gentamicin presented from PEMs enhances the antimicrobial properties of the surfaces without inhibiting hADSC attachment and cell growth. Delivering gentamicin from the surfaces is therefore superior to delivering gentamicin in solution and represents a strategy that could improve the antimicrobial activity of orthopedic implants and reduce risk of failure due to infection, without reducing mammalian cell attachment.

Oxygen-Vacancy Abundant Nanoporous Ni/NiMnO3/MnO2@NiMn Electrodes with Ultrahigh Capacitance and Energy Density for Supercapacitors

High-performance energy storage devices (HPEDs) play a critical role in the realization of clean energy and thus enable the overarching pursuit of nonpolluting, green technologies. Supercapacitors are one class of such lucrative HPEDs; however, a serious limiting factor of supercapacitor technology is its sub-par energy density. This report presents hitherto unchartered pathway of physical deformation, chemical dealloying, and microstructure engineering to produce ultrahigh-capacitance, energy-dense NiMn alloy electrodes. The activated electrode delivered an ultrahigh specific-capacitance of 2700 F/cm³ at 0.5 A/cm³. The symmetric device showcased an excellent energy density of 96.94 Wh/L and a remarkable cycle life of 95% retention after 10,000 cycles. Transmission electron microscopy and atom probe tomography studies revealed the evolution of a unique hierarchical microstructure comprising fine Ni/NiMnO₃ nanoligaments within MnO₂-rich nanoflakes. Theoretical analysis using density functional theory showed semimetallic nature of the nanoscaled oxygen-vacancy-rich NiMnO₃ structure, highlighting enhanced carrier concentration and electronic conductivity of the active region. Furthermore, the geometrical model of NiMnO₃ crystals revealed relatively large voids, likely providing channels for the ion intercalation/de-intercalation. The current processing approach is highly adaptable and can be applied to a wide range of material systems for designing highly efficient electrodes for energy-storage devices.

The Effect of Anterior Cruciate Ligament Reconstruction with an Electropsun Scaffold on Tibiofemoral Contact Mechanics

Surgical reconstruction of the torn ACL is performed to restore native contact mechanics. Drawbacks to traditional ACL repair techniques motivate the development of a tissue engineered ACL scaffold. Our group has developed a hierarchical electrospun polycaprolactone (PCL) scaffold that consists of rolled nanofiber bundles attached at each end with solvent-case blocks of PCL. The goal of this study was to compare ovine cadaver tibiofemoral contact mechanics after ACL reconstruction with the electrospun scaffold to a clinically applicable ACL reconstruction with a soft tissue graft and the ACL transected condition (ACLX). In the ACLX group and after ACL reconstruction with either the electrospun scaffold or soft tissue graft, pressure sensors were inserted under the menisci. Loads up to 890 N were applied at various flexion angles. The scaffold performed the best at restoring contact mechanics in the medial hemijoint to that of the native ACL. The scaffold was good at maintaining a medial-lateral balance of pressures as in the native joint whereas the ACLX shifted pressure off the lateral and on to the medial hemijoint. While the ACL scaffold didn't restore mechanics to that of the native condition, it improved contact mechanics compared to the standard graft replacement and ACLX condition.

Excellent Electroluminescent Property of Eu3+-Induced Polystyrene-co-poly(acrylic acid) Aggregates (EIPAs) in Polymeric Light-Emitting Diodes

Eu3+-induced polystyrene-co-poly(acrylic acid) aggregates (EIPAs) were synthesized using a self-assembly approach, and their structures and photophysical characteristics were examined to achieve effective monochromatic red emission in polymer light-emitting diodes (PLEDs). By adjusting the monomer ratio in RAFT polymerization, the size of Eu3+-induced block copolymer nanoaggregates can be regulated, thereby modulating the luminescence intensity. High-performance bilayer polymer light-emitting devices were fabricated using poly(9,9-dioctylfluorene) (PFO) and 2-(tert-butylphenyl)-5-biphenylyl-1,3,4-oxadiazole (PBD) as the host matrix, with EIPAs as the guest dopant. The devices exhibited narrow red emission at 615 nm with a full width at half-maximum (fwhm) of 15 nm across doping concentrations of 1, 3, 5, and 10 wt %. At a doping concentration of 3 wt %, the device achieved a maximum brightness of 1864.48 cd/m2 at 193.82 mA/cm2 and an external quantum efficiency of 3.20% at a current density of 3.5 mA/cm2. These results indicate that incorporating polystyrene-co-poly(acrylic acid) with Eu3+ complexes enhances the excitation and emission intensity, as well as the structural stability of the emitting layer in PLEDs, thereby improving the device performance.

Paraplegia following intra-aortic balloon support. Report of a case

A case is presented of paraplegia associated with the intra-aortic balloon pump used in a post-operative patient. The published experience with this complication is reviewed.

Stainless steel and titanium alloys coated with sulfated chitosan to improve hemocompatibility properties

The main drawbacks of blood-contacting metallic devices are corrosion and thrombus formation on the surface, so polymeric coatings have been proposed to improve its hemocompatibility. Sulfated chitosan (SC) was obtained from natural chitosan (NC) reaction with chlorosulfonic acid to be used as a coating for metallic surfaces. The sulfated chitosan showed no platelet aggregation, an extended clotting time, and non-toxicity to rat fibroblast L929 cells. In this study, stainless steel (SS) and titanium alloys modified with TiO2 nanotube (NTT) growth received a NC and SC coating. The titanium surface coated with sulfated chitosan presented the lowest percentage of platelet coverage area. Sulfated chitosan proved to be a promising material for use as a coating for metallic surfaces applied for cardiovascular devices.

Antimicrobial and Antiproliferative Coatings for Stents in Veterinary Medicine-State of the Art and Perspectives

Microbial colonization in veterinary stents poses a significant and concerning issue in veterinary medicine. Over time, these pathogens, particularly bacteria, can colonize the stent surfaces, leading to various complications. Two weeks following the stent insertion procedure, the colonization becomes observable, with the aggressiveness of bacterial growth directly correlating with the duration of stent placement. Such microbial colonization can result in infections and inflammations, compromising the stent's efficacy and, subsequently, the animal patient's overall well-being. Managing and mitigating the impact of these pathogens on veterinary stents is a crucial challenge that veterinarians and researchers are actively addressing to ensure the successful treatment and recovery of their animal patients. In addition, irritation of the tissue in the form of an inserted stent can lead to overgrowth of granulation tissue, leading to the closure of the stent lumen, as is most often the case in the trachea. Such serious complications after stent placement require improvements in the procedures used to date. In this review, antibacterial or antibiofilm strategies for several stents used in veterinary medicine have been discussed based on the current literature and the perspectives have been drawn. Various coating strategies such as coating with hydrogel, antibiotic, or other antimicrobial agents have been reviewed.