Study protocol for IMAGE: implementing multidisciplinary assessments for geriatric patients in an emergency department observation unit, a hybrid effectiveness/implementation study using the Consolidated Framework for Implementation Research.

BACKGROUND: Older adults in the emergency department (ED) are at high risk for functional decline, unrecognized delirium, falls, and medication interactions. Holistic assessment by a multidisciplinary team in the ED decreases these adverse outcomes and decreases admissions, but there are many barriers to incorporating this type of care during the ED visit. METHODS: This is a hybrid type II effectiveness-implementation study using a pre-/post-cohort design (n = 380) at a tertiary care academic ED with an ED observation unit (Obs Unit). The intervention is a two-step protocol of (step 1) ED nurses screening adult patients ≥ 65 years old for geriatric needs using the Delirium Triage Screen, 4-Stage Balance Test, and the Identifying Seniors at Risk score. Patients who have geriatric needs identified by this screening but who do not meet hospital admission criteria will (step 2) be placed in the Obs Unit for multidisciplinary geriatric assessment by the hospital's geriatric consultation team, physical therapists, occupational therapists, pharmacists, and/or case managers. Not all patients may require all elements of the multidisciplinary geriatric assessment. The Consolidated Framework for Implementation Research: Care Transitions Framework was used to identify barriers to implementation. Lean Six Sigma processes will be used to overcome these identified barriers with the goal of achieving geriatric screening rates of > 80%. Implementation success and associated factors will be reported. For the effectiveness aim, pre-/post-cohorts of adults ≥ 65 years old cared for in the Obs Unit will be followed for 90 days post-ED visit (n = 150 pre and 230 post). The primary outcome is the prevention of functional decline. Secondary outcomes include health-related quality of life, new geriatric syndromes identified, new services provided, and Obs Unit metrics such as length of stay and admission rates. DISCUSSION: A protocol for implementing integrated multidisciplinary geriatric assessment into the ED setting has the potential to improve patient functional status by identifying and addressing geriatric issues and needs prior to discharge from the ED. Using validated frameworks and implementation strategies will increase our understanding of how to improve the quality of ED care for older adults in the acute care setting. TRIAL REGISTRATION: ClinicalTrials.gov Identifier, NCT04068311, registered 28 August 2019.

Circulating Gasdermin-D in Critically Ill Patients.

The key to further improving outcomes in sepsis lies in understanding and abrogating the dysfunctional immune response that leads to organ failure. Activation of gasdermin-D, a pore-forming protein within the inflammasome cascade, has recently been recognized as the critical step in pyroptosis and organ dysfunction. In this study, we sought to investigate the presence of gasdermin-D in critically ill subjects. DESIGN SETTING AND PATIENTS: Prospective pilot study comparing microparticulate active gasdermin-D levels in critically ill patients admitted to the medical ICU at The Ohio State University Medical Center to healthy donors and clinical outcomes. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Plasma was collected from subjects upon consent and microparticles were isolated by ultracentrifugation. Proteins of interest were identified by immunoblot analysis of microparticle lysates. Quantification was accomplished by densitometry using ImageJ software (National Institutes of Health, Bethesda, MD). Investigators were then unblinded and compared microparticulate active gasdermin-D levels to physician adjudicated clinical diagnoses and outcomes. No appreciable levels of active gasdermin-D were observed in microparticles from healthy volunteers and nonseptic critically ill patients. However, elevated levels of gasdermin-D were noted in microparticles from the septic cohort of critically ill patients. Furthermore, a significant positive correlation by linear regression was noted when microparticulate active gasdermin-D levels were compared with microparticulate levels of CD63, an exosomal marker, CD14, a monocyte marker, and CD69, a marker of monocyte activation (R 2 = 0.37, p = 0.0011, R 2 = 0.85, p < 0.0001, and R2 = 0.43, p = 0.0003, respectively). CONCLUSIONS: This is the first study to demonstrate circulating active gasdermin-D in septic patients in the intensive care setting. Our findings also suggest that active gasdermin-D in septic patients is encapsulated in exosomes derived from activated monocytes. Further characterization in the clinical setting is warranted.

Novel ImPACT validity indices in collegiate student-athletes with and without histories of ADHD or academic difficulties.

Objective: Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) assesses neurocognitive functioning in sports-related concussion. Previous work demonstrates ImPACT's validity indices detect poor effort at disproportionately higher rates in athletes with histories of attention deficit hyperactivity disorder (ADHD) or academic difficulties. The present study examines whether previously suggested 'dormant' validity indices, Word Memory Correct Distractors (WMCD), and Design Memory Correct Distractors (DMCD), reduce disproportionate invalidity in collegiate athletes with such histories.Method: Six seasons of ImPACT protocols were examined (n = 1727). Athletes were grouped by self-reported histories of ADHD, academic difficulties, or comorbid ADHD and academic difficulties. Chi-square analyses compared invalidity rates using existing validity indices and both standard and conservative cutoffs for WMCD and DMCD.Results: Using standard cutoffs for dormant indices (WMCD < 22, DMCD < 16) produced significant differences in rates of athletes identified as having an invalid protocol, with the comorbid group exhibiting the highest invalidity rate (63.2%) and the no history group producing the lowest (42.0%), χ2 (3) = 11.57, p < .01, Cramer's V = 0.08. This difference remained when utilizing conservative cutoffs (WMCD < 18, DMCD < 10), with the comorbid group again producing the highest (26.3%) and the no history group producing the lowest (10.4%), χ2 (3) = 15.64, p < .005, Cramer's V = 0.10.Conclusions: Student-athletes with self-reported histories of ADHD and academic difficulties are more likely to produce invalid protocols, even with dormant indices. These findings emphasize the difficulty in assessing validity in special populations of athletes and encourage further work in this area.

Reprint of: Pendant allyl crosslinking as a tunable shape memory actuator for vascular applications.

Thermo-responsive shape memory polymers (SMPs) can be programmed to fit into small-bore incisions and recover their functional shape upon deployment in the body. This property is of significant interest for developing the next generation of minimally-invasive medical devices. To be used in such applications, SMPs should exhibit adequate mechanical strengths that minimize adverse compliance mismatch-induced host responses (e.g. thrombosis, hyperplasia), be biodegradable, and demonstrate switch-like shape recovery near body temperature with favorable biocompatibility. Combinatorial approaches are essential in optimizing SMP material properties for a particular application. In this study, a new class of thermo-responsive SMPs with pendant, photocrosslinkable allyl groups, x%poly(ε-caprolactone)-co-y%(α-allyl carboxylate ε-caprolactone) (x%PCL-y%ACPCL), are created in a robust, facile manner with readily tunable material properties. Thermomechanical and shape memory properties can be drastically altered through subtle changes in allyl composition. Molecular weight and gel content can also be altered in this combinatorial format to fine-tune material properties. Materials exhibit highly elastic, switch-like shape recovery near 37 °C. Endothelial compatibility is comparable to tissue culture polystyrene (TCPS) and 100%PCL in vitro and vascular compatibility is demonstrated in vivo in a murine model of hindlimb ischemia, indicating promising suitability for vascular applications. STATEMENT OF SIGNIFICANCE: With the ongoing thrust to make surgeries minimally-invasive, it is prudent to develop new biomaterials that are highly compatible and effective in this workflow. Thermo-responsive shape memory polymers (SMPs) have great potential for minimally-invasive applications because SMP medical devices (e.g. stents, grafts) can fit into small-bore minimally-invasive surgical devices and recover their functional shape when deployed in the body. To realize their potential, it is imperative to devise combinatorial approaches that enable optimization of mechanical, SM, and cellular responses for a particular application. In this study, a new class of thermo-responsive SMPs is created in a robust, facile manner with readily tunable material properties. Materials exhibit excellent, switch-like shape recovery near body temperature and promising biocompatibility for minimally-invasive vascular applications.

Pendant allyl crosslinking as a tunable shape memory actuator for vascular applications.

Thermo-responsive shape memory polymers (SMPs) can be programmed to fit into small-bore incisions and recover their functional shape upon deployment in the body. This property is of significant interest for developing the next generation of minimally-invasive medical devices. To be used in such applications, SMPs should exhibit adequate mechanical strengths that minimize adverse compliance mismatch-induced host responses (e.g. thrombosis, hyperplasia), be biodegradable, and demonstrate switch-like shape recovery near body temperature with favorable biocompatibility. Combinatorial approaches are essential in optimizing SMP material properties for a particular application. In this study, a new class of thermo-responsive SMPs with pendant, photocrosslinkable allyl groups, x%poly(ε-caprolactone)-co-y%(α-allyl carboxylate ε-caprolactone) (x%PCL-y%ACPCL), are created in a robust, facile manner with readily tunable material properties. Thermomechanical and shape memory properties can be drastically altered through subtle changes in allyl composition. Molecular weight and gel content can also be altered in this combinatorial format to fine-tune material properties. Materials exhibit highly elastic, switch-like shape recovery near 37°C. Endothelial compatibility is comparable to tissue culture polystyrene (TCPS) and 100%PCL in vitro and vascular compatibility is demonstrated in vivo in a murine model of hindlimb ischemia, indicating promising suitability for vascular applications. STATEMENT OF SIGNIFICANCE: With the ongoing thrust to make surgeries minimally-invasive, it is prudent to develop new biomaterials that are highly compatible and effective in this workflow. Thermo-responsive shape memory polymers (SMPs) have great potential for minimally-invasive applications because SMP medical devices (e.g. stents, grafts) can fit into small-bore minimally-invasive surgical devices and recover their functional shape when deployed in the body. To realize their potential, it is imperative to devise combinatorial approaches that enable optimization of mechanical, SM, and cellular responses for a particular application. In this study, a new class of thermo-responsive SMPs is created in a robust, facile manner with readily tunable material properties. Materials exhibit excellent, switch-like shape recovery near body temperature and promising biocompatibility for minimally-invasive vascular applications.

ROS-cleavable proline oligomer crosslinking of polycaprolactone for pro-angiogenic host response.

A reactive oxygen species (ROS)-degradable scaffold is fabricated by crosslinking biocompatible, hydrolytically-degradable poly(ε-caprolactone) (PCL) with a ROS-degradable oligoproline peptide, KP7K. The ROS-mediated degradability triggers favorable host responses of the scaffold including improved cell infiltration and angiogenesis in vivo, indicating its unique advantages for tissue engineering applications.

Uncoupling angiogenesis and inflammation in peripheral artery disease with therapeutic peptide-loaded microgels.

Peripheral artery disease (PAD) is characterized by vessel occlusion and ischemia in the limbs. Treatment for PAD with surgical interventions has been showing limited success. Moreover, recent clinical trials with treatment of angiogenic growth factors proved ineffective as increased angiogenesis triggered severe inflammation in a proportionally coupled fashion. Hence, the overarching goal of this research was to address this issue by developing a biomaterial system that enables controlled, dual delivery of pro-angiogenic C16 and anti-inflammatory Ac-SDKP peptides in a minimally-invasive way. To achieve the goal, a peptide-loaded injectable microgel system was developed and tested in a mouse model of PAD. When delivered through multiple, low volume injections, the combination of C16 and Ac-SDKP peptides promoted angiogenesis, muscle regeneration, and perfusion recovery, while minimizing detrimental inflammation. Additionally, this peptide combination regulated inflammatory TNF-α pathways independently of MMP-9 mediated pathways of angiogenesis in vitro, suggesting a potential mechanism by which angiogenic and inflammatory responses can be uncoupled in the context of PAD. This study demonstrates a translatable potential of the dual peptide-loaded injectable microgel system for PAD treatment.

Polymeric stent materials dysregulate macrophage and endothelial cell functions: implications for coronary artery stent.

BACKGROUND: Biodegradable polymers have been applied as bulk or coating materials for coronary artery stents. The degradation of polymers, however, could induce endothelial dysfunction and aggravate neointimal formation. Here we use polymeric microparticles to simulate and demonstrate the effects of degraded stent materials on phagocytic activity, cell death and dysfunction of macrophages and endothelial cells. METHODS: Microparticles made of low molecular weight polyesters were incubated with human macrophages and coronary artery endothelial cells (ECs). Microparticle-induced phagocytosis, cytotoxicity, apoptosis, cytokine release and surface marker expression were determined by immunostaining or ELISA. Elastase expression was analyzed by ELISA and the elastase-mediated polymer degradation was assessed by mass spectrometry. RESULTS: We demonstrated that poly(D,L-lactic acid) (PLLA) and polycaprolactone (PCL) microparticles induced cytotoxicity in macrophages and ECs, partially through cell apoptosis. The particle treatment alleviated EC phagocytosis, as opposed to macrophages, but enhanced the expression of vascular cell adhesion molecule (VCAM)-1 along with decreased nitric oxide production, indicating that ECs were activated and lost their capacity to maintain homeostasis. The activation of both cell types induced the release of elastase or elastase-like protease, which further accelerated polymer degradation. CONCLUSIONS: This study revealed that low molecule weight PLLA and PCL microparticles increased cytotoxicity and dysregulated endothelial cell function, which in turn enhanced elastase release and polymer degradation. These indicate that polymer or polymer-coated stents impose a risk of endothelial dysfunction after deployment which can potentially lead to delayed endothelialization, neointimal hyperplasia and late thrombosis.

Combined usage of stem cells in end-stage heart failure therapies.

Remarkable achievements have been made in the clinical application of mechanical circulatory support and cardiac transplantation for patients with end-stage heart failure. Despite the successes, complications associated with these therapies continue to drive cardiac regenerative research utilizing stem cell based therapies. Multiple stem cell lineages hold clinical promise for cardiac regeneration-mostly through cellular differentiation, cellular fusion, and paracrine signaling mechanisms. Bone marrow-derived endothelial progenitor cells are among the most intriguing and controversial cell types currently being investigated. Formidable barriers exist, however, in finding the ideal cardiac regenerative stem cell, such as identifying specific lineage markers, optimizing in vitro cellular expansion and improving methods of stem cell delivery. Hybrid approaches of cardiac regeneration using stem cell therapies in conjunction with immunomodulation after cardiac transplantation or with mechanical circulatory support produce cutting edge stem cell technologies. This review summarizes the current knowledge and therapeutic applications of stem cells in patients with end-stage heart failure, including stem cell therapy after implantation of mechanical circulatory support and cardiac transplantation.

Femtosecond laser-patterned nanopore arrays for surface-mediated peptide treatment.

The major goal of this study was to create easy-to-use, reusable substrates capable of storing any peptides or bioactive molecules for a desired period of time until cells uptake them without the need for bioactive molecule or peptide-specific techniques. Nanopore arrays of uniform size and distribution were machined into fused silica substrates using femtosecond laser ablation and loaded with peptides by simple adsorption. The nanopore substrates were validated by examining the effect of N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) loaded nanopores on macrophage phagocytosis and intracellular production of reactive oxygen species (ROS) with and without the pro-inflammatory lipopolysaccharide (LPS). Our results demonstrated that nanopores were generated in a uniform array fashion. Ac-SDKP peptides were stably stored in nanopores and internalized by macrophages. Significant reductions in ROS production and phagocytosis in macrophages were observed over control substrates, even in combination with LPS stimulation, indicating that loading Ac-SDKP peptides in pores significantly improved the anti-inflammatory effects. FROM THE CLINICAL EDITOR: This team of scientists intended to create easy-to-use, reusable substrates for storing peptides or bioactive molecules for a desired period of time before cellular uptake occurs, and without the need for bioactive molecule or peptide-specific techniques. They demonstrate the successful generation of nanopores in a uniform array that stably stores Ac-SDKP peptides in the nanopores. When peptides were internalized by macrophages, significant reductions in ROS production and phagocytosis were observed, indicating improved anti-inflammatory effects.

Pro-angiogenic and anti-inflammatory regulation by functional peptides loaded in polymeric implants for soft tissue regeneration.

Inflammation and angiogenesis are inevitable in vivo responses to biomaterial implants. Continuous progress has been made in biomaterial design to improve tissue interactions with an implant by either reducing inflammation or promoting angiogenesis. However, it has become increasingly clear that the physiological processes of inflammation and angiogenesis are interconnected through various molecular mechanisms. Hence, there is an unmet need for engineering functional tissues by simultaneous activation of pro-angiogenic and anti-inflammatory responses to biomaterial implants. In this work, the modulus and fibrinogen adsorption of porous scaffolds were tuned to meet the requirements (i.e., ~100 kPa and ~10 nm, respectively), for soft tissue regeneration by employing tyrosine-derived combinatorial polymers with polyethylene glycol crosslinkers. Two types of functional peptides (i.e., pro-angiogenic laminin-derived C16 and anti-inflammatory thymosin ß4-derived Ac-SDKP) were loaded in porous scaffolds through collagen gel embedding so that peptides were released in a controlled fashion, mimicking degradation of the extracellular matrix. The results from (1) in vitro coculture of human umbilical vein endothelial cells and human blood-derived macrophages and (2) in vivo subcutaneous implantation revealed the directly proportional relationship between angiogenic activities (i.e., tubulogenesis and perfusion capacity) and inflammatory activities (i.e., phagocytosis and F4/80 expression) upon treatment with either type of peptide. Interestingly, cotreatment with both types of peptides upregulated the angiogenic responses, while downregulating the inflammatory responses. Also, anti-inflammatory Ac-SDKP peptides reduced production of pro-inflammatory cytokines (i.e., interleukin [IL]-1ß, IL-6, IL-8, and tumor necrosis factor alpha) even when treated in combination with pro-angiogenic C16 peptides. In addition to independent regulation of angiogenesis and inflammation, this study suggests a promising approach to improve soft tissue regeneration (e.g., blood vessel and heart muscle) when inflammatory diseases (e.g., ischemic tissue fibrosis and atherosclerosis) limit the regeneration process.

Elucidation of adhesion-dependent spontaneous apoptosis in macrophages using phase separated PEG/polyurethane films.

Circulating monocytes undergo spontaneous apoptosis when there is no activation stimulus, which is critical to population control for proper host response to implants. As activation and apoptosis of monocytes/macrophages are regulated by cell-cell and cell-matrix interactions, their regulatory mechanism was investigated in this study using polyethylene glycol (PEG)-containing polyurethane films in which PEG-rich and polyester-rich domains were phase separated. Human blood monocyte-derived macrophages (HBMs) preferentially adhered to PEG domains (cell-matrix interaction) due to the low molecular weight (600 g mol⁻¹), resulting in increased HBM density (cell-cell interaction). As both cell-cell and cell-matrix interactions were promoted, HBM apoptosis increased, while their activation as measured by phagocytosis, intracellular reactive oxygen species (ROS) level and matrix metalloproteinase-9 production decreased compared to PEG-free films. When cell seeding density and cell-adhesive gelatin coating on silicone films were controlled, a cooperative role of cell-matrix (adhesion) and cell-cell (density) interactions in inducing HBM apoptosis was observed. Expression of the macrophage adhesion molecule CD11b caused apoptosis in this context, which was mediated by tissue necrosis factor-α signaling but down-regulated by the ROS inhibitor diphenylene iodonium and the anti-inflammatory peptide Ac-SDKP, suggesting a new concept for the design of biomaterials that allows for cell adhesion without excessive inflammatory activation.

Decoupling polymer properties to elucidate mechanisms governing cell behavior.

Determining how a biomaterial interacts with cells ("structure-function relationship") reflects its eventual clinical applicability. Therefore, a fundamental understanding of how individual material properties modulate cell-biomaterial interactions is pivotal to improving the efficacy and safety of clinically translatable biomaterial systems. However, due to the coupled nature of material properties, their individual effects on cellular responses are difficult to understand. Structure-function relationships can be more clearly understood by the effective decoupling of each individual parameter. In this article, we discuss three basic decoupling strategies: (1) surface modification, (2) cross-linking, and (3) combinatorial approaches (i.e., copolymerization and polymer blending). Relevant examples of coupled material properties are briefly reviewed in each section to highlight the need for improved decoupling methods. This follows with examples of more effective decoupling techniques, mainly from the perspective of three primary classes of synthetic materials: polyesters, polyethylene glycol, and polyacrylamide. Recent strides in decoupling methodologies, especially surface-patterning and combinatorial techniques, offer much promise in further understanding the structure-function relationships that largely govern the success of future advancements in biomaterials, tissue engineering, and drug delivery.

Modular polymer design to regulate phenotype and oxidative response of human coronary artery cells for potential stent coating applications.

Polymer properties can be tailored by copolymerizing subunits with specific physico-chemical characteristics. Vascular stent materials require biocompatibility, mechanical strength, and prevention of restenosis. Here we copolymerized poly(ε-caprolactone) (PCL), poly(ethylene glycol) (PEG), and carboxyl-PCL (cPCL) at varying molar ratios and characterized the resulting material properties. We then performed a short-term evaluation of these polymers for their applicability as potential coronary stent coating materials with two primary human coronary artery cell types: smooth muscle cells (HCASMC) and endothelial cells (HCAEC). Changes in proliferation and phenotype were dependent upon intracellular reactive oxygen species (ROS) levels, and 4%PEG-96%PCL-0%cPCL was identified as the most appropriate coating material for this application. After 3days on this substrate HCASMC maintained a healthy contractile phenotype and HCAEC exhibited a physiologically relevant proliferation rate and a balanced redox state. Other test substrates promoted a pathological, synthetic phenotype of HCASMC and/or hyperproliferation of HCAEC. Phenotypic changes of HCASMC appeared to be modulated by the Young's modulus and surface charge of the test substrates, indicating a structure-function relationship that can be exploited for intricate control over vascular cell functions. These data indicate that tailored copolymer properties can direct vascular cell behavior and provide insights for further development of biologically instructive stent coating materials.

Physiologically relevant oxidative degradation of oligo(proline) cross-linked polymeric scaffolds.

Chronic inflammation-mediated oxidative stress is a common mechanism of implant rejection and failure. Therefore, polymer scaffolds that can degrade slowly in response to this environment may provide a viable platform for implant site-specific, sustained release of immunomodulatory agents over a long time period. In this work, proline oligomers of varying lengths (P(n)) were synthesized and exposed to oxidative environments, and their accelerated degradation under oxidative conditions was verified via high performance liquid chromatography and gel permeation chromatography. Next, diblock copolymers of poly(ethylene glycol) (PEG) and poly(ε-caprolactone) (PCL) were carboxylated to form 100 kDa terpolymers of 4%PEG-86%PCL-10%cPCL (cPCL = poly(carboxyl-ε-caprolactone); i% indicates molar ratio). The polymers were then cross-linked with biaminated PEG-P(n)-PEG chains, where P(n) indicates the length of the proline oligomer flanked by PEG chains. Salt-leaching of the polymeric matrices created scaffolds of macroporous and microporous architecture, as observed by scanning electron microscopy. The degradation of scaffolds was accelerated under oxidative conditions, as evidenced by mass loss and differential scanning calorimetry measurements. Immortalized murine bone-marrow-derived macrophages were then seeded on the scaffolds and activated through the addition of γ-interferon and lipopolysaccharide throughout the 9-day study period. This treatment promoted the release of H(2)O(2) by the macrophages and the degradation of proline-containing scaffolds compared to the control scaffolds. The accelerated degradation was evidenced by increased scaffold porosity, as visualized through scanning electron microscopy and X-ray microtomography imaging. The current study provides insight into the development of scaffolds that respond to oxidative environments through gradual degradation for the controlled release of therapeutics targeted to diseases that feature chronic inflammation and oxidative stress.

Characterization of the degradation mechanisms of lysine-derived aliphatic poly(ester urethane) scaffolds.

Characterization of the degradation mechanism of polymeric scaffolds and delivery systems for regenerative medicine is essential to assess their clinical applicability. Key performance criteria include induction of a minimal, transient inflammatory response and controlled degradation to soluble non-cytotoxic breakdown products that are cleared from the body by physiological processes. Scaffolds fabricated from biodegradable poly(ester urethane)s (PEURs) undergo controlled degradation to non-cytotoxic breakdown products and support the ingrowth of new tissue in preclinical models of tissue regeneration. While previous studies have shown that PEUR scaffolds prepared from lysine-derived polyisocyanates degrade faster under in vivo compared to in vitro conditions, the degradation mechanism is not well understood. In this study, we have shown that PEUR scaffolds prepared from lysine triisocyanate (LTI) or a trimer of hexamethylene diisocyanate (HDIt) undergo hydrolytic, esterolytic, and oxidative degradation. Hydrolysis of ester bonds to yield α-hydroxy acids is the dominant mechanism in buffer, and esterolytic media modestly increase the degradation rate. While HDIt scaffolds show a modest (<20%) increase in degradation rate in oxidative medium, LTI scaffolds degrade six times faster in oxidative medium. Furthermore, the in vitro rate of degradation of LTI scaffolds in oxidative medium approximates the in vivo rate in rat excisional wounds, and histological sections show macrophages expressing myeloperoxidase at the material surface. While recent preclinical studies have underscored the potential of injectable PEUR scaffolds and delivery systems for tissue regeneration, this promising class of biomaterials has a limited regulatory history. Elucidation of the macrophage-mediated oxidative mechanism by which LTI scaffolds degrade in vivo provides key insights into the ultimate fate of these materials when injected into the body.

Effects of topography on the functional development of human neural progenitor cells.

We have fabricated a topographical substrate with a packed polystyrene bead array for the development of cell-based assay systems targeting voltage-gated calcium channels (VGCCs). Human neural progenitor cells (H945RB.3) cultured on both flat and topographical substrates were analyzed in terms of morphological spreading, neuronal commitment, resting membrane potential (V(m)) establishment and VGCC function development. We found, by SEM imaging, that arrayed substrates, formed with both sub-micrometer (of 0.51 microm in mean diameter) and micrometer (of 1.98 microm in mean diameter) beads, were capable of promoting the spreading of the progenitor cells as compared with the flat polystyrene surfaces. With the micrometer beads, it was found that arrayed substrates facilitated the neural progenitor cells' maintenance of less negative V(m) values upon differentiation with bFGF starvation, which favored predominant neuronal commitment. Almost all the progenitor cells were responsive to 50 mM K(+) depolarization with an increase in [Ca(2+)](i) either before or upon differentiation, suggesting the expression of functional VGCCs. Compared to the flat polystyrene surfaces, microbead arrayed substrates facilitated the development of higher VGCC responsiveness by the progenitor cells upon differentiation. The enhancement of both VGCC responsiveness and cell spreading by arrays of micrometer beads was most significant on day 14 into differentiation, which was the latest time point of measurement in this study. This study thus rationalized the possibility for future substrate topography engineering to manipulate ion channel function and to meet the challenge of low VGCC responsiveness found in early drug discovery.