Degradation behaviour of porous poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) scaffolds in cell culture.

Exploring the degradation behaviour of biomaterials in a complex in vitro physiological environment can assist in predicting their performance in vivo, yet this aspect remains largely unexplored. In this study, the in vitro degradation over 12 weeks of porous poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) bone scaffolds in human osteoblast (hOB) culture was investigated. The objective was to evaluate how the presence of cells influenced both the degradation behaviour and mechanical stability of these scaffolds. The molecular weight (Mw) of the scaffolds decreased with increasing incubation time and the Mw reduction rate (6.2 ± 0.4 kg mol-1 week-1) was similar to that observed when incubated in phosphate buffered saline (PBS) solution, implying that the scaffolds underwent hydrolytic degradation in hOB culture. The mass of the scaffolds increased by 0.8 ± 0.2 % in the first 4 weeks, attributed to cells attachment and extracellular matrix (ECM) deposition including biomineralisation. During the first 8 weeks, the nominal compressive modulus, E⁎, of the scaffolds remained constant. However, it increased significantly from Week 8 to 12, with increments of 55 % and 42 % in normal and lateral directions, respectively, attributed to the reinforcement effect of cells, ECM and minerals attached on the surface of the scaffold. This study has highlighted, that while the use of PBS in degradation studies is suitable for evaluating Mw changes it cannot predict changes in mechanical properties to PHBV scaffolds in the presence of cells and culture media. Furthermore, the PHBV scaffolds had mechanical stability in cell culture for 12 weeks validating their suitability for tissue engineering applications.

In vitro evaluation of porous poly(hydroxybutyrate-co-hydroxyvalerate)/akermanite composite scaffolds manufactured using selective laser sintering.

Incorporation of a bioactive mineral filler in a biodegradable polyester scaffold is a promising strategy for scaffold assisted bone tissue engineering (TE). The current study evaluates the in vitro behavior of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)/Akermanite (AKM) composite scaffolds manufactured using selective laser sintering (SLS). Exposure of the mineral filler on the surface of the scaffold skeleton was evident from in vitro mineralization in PBS. PHBV scaffolds and solvent cast films served as control samples and all materials showed preferential adsorption of fibronectin compared to serum albumin as well as non-cytotoxic response in human osteoblasts (hOB) at 24 h. hOB culture for up to 21 days revealed that the metabolic activity in PHBV films and scaffolds was significantly higher than that of PHBV/AKM scaffolds within the first two weeks of incubation. Afterwards, the metabolic activity in PHBV/AKM scaffolds exceeded that of the control samples. Confocal imaging showed cell penetration into the porous scaffolds. Significantly higher ALP activity was observed in PHBV/AKM scaffolds at all time points in both basal and osteogenic media. Mineralization during cell culture was observed on all samples with PHBV/AKM scaffolds exhibiting distinctly different mineral morphology. This study has demonstrated that the bioactivity of PHBV SLS scaffolds can be enhanced by incorporating AKM, making this an attractive candidate for bone TE application.

Establishment of ion channel and ABC transporter assays in 3D-cultured ReNcell VM on a 384-pillar plate for neurotoxicity potential.

Neurotoxicity potential of compounds by inhibition of ion channels and efflux transporters has been studied traditionally using two-dimensionally (2D) cultured cell lines such as CHO and HEK-293 overexpressing the protein of interest. However, these approaches are time consuming and do not recapitulate the activity of ion channels and efflux transporters indigenously expressed in neural stem cells (NSCs) in vivo. To overcome these issues, we established ion channel and transporter assays on a 384-pillar plate with three-dimensionally (3D) cultured ReNcell VM and demonstrated high-throughput measurement of ion channel and transporter activity. RNA sequencing analysis identified major ion channels and efflux transporters expressed in ReNcell VM, followed by validating 3D ReNcell-based ion channel and transporter assays with model compounds. Major ion channel activities were measured by specifically inhibiting potassium channels Kv 7.2 with XE-991 and Kv 4.3 with fluoxetine, and a calcium channel with 2-APB. Activities of major efflux transporters, MDR1, MRP1, and BCRP, were assessed using their respective blockers, verapamil, probenecid, and novobiocin. From this study, we demonstrated that 3D-cultured ReNcell VM on the 384-pillar plate could be a good alternative to rapidly identify environmental chemicals and therapeutic compounds for their role in modulating the activity of ion channels and efflux transporters, potentially leading to neurotoxicity.

Discrete element and finite element methods provide similar estimations for hip joint contact mechanics during walking gait.

Finite element analysis (FEA) provides a powerful approach for estimating the in-vivo loading characteristics of the hip joint during various locomotory and functional activities. However, time-consuming procedures, such as the generation of high-quality FE meshes and setup of FE simulation, typically make the method impractical for rapid applications which could be used in clinical routine. Alternatively, discrete element analysis (DEA) has been developed to quantify mechanical conditions of the hip joint in a fraction of time compared to FEA. Although DEA has proven effective in the estimation of contact stresses and areas in various complex applications, it has not yet been well characterised by its ability to evaluate contact mechanics for the hip joint during gait cycle loading using data from several individuals. The objective of this work was to compare DEA modelling against well-established FEA for analysing contact mechanics of the hip joint during walking gait. Subject-specific models were generated from magnetic resonance images of the hip joints in five asymptomatic subjects. The DEA and FEA models were then simulated for 13 loading time-points extracted from a full gait cycle. Computationally, DEA was substantially more efficient compared to FEA (simulation times of seconds vs. hours). The DEA and FEA methods had similar predictions for contact pressure distribution for the hip joint during normal walking. In all 13 simulated loading time-points across five subjects, the maximum difference in average contact pressures between DEA and FEA was within ±0.06 MPa. Furthermore, the difference in contact area ratio computed using DEA and FEA was less than ±6%.

TiB Nanowhisker Reinforced Titanium Matrix Composite with Improved Hardness for Biomedical Applications.

Titanium and its alloys have been employed in the biomedical industry as implants and show promise for more broad applications because of their excellent mechanical properties and low density. However, high cost, poor wear properties, low hardness and associated side effects caused by leaching of alloy elements in some titanium alloys has been the bottleneck to their wide application. TiB reinforcement has shown promise as both a surface coating for Ti implants and also as a composite reinforcement phase. In this study, a low-cost TiB-reinforced alpha titanium matrix composite (TMC) is developed. The composite microstructure includes ultrahigh aspect ratio TiB nanowhiskers with a length up to 23 µm and aspect ratio of 400 and a low average Ti grain size. TiB nanowhiskers are formed in situ by the reaction between Ti and BN nanopowder. The TMC exhibited hardness of above 10.4 GPa, elastic modulus above 165 GPa and hardness to Young's modulus ratio of 0.062 representing 304%, 170% and 180% increases in hardness, modulus and hardness to modulus ratio, respectively, when compared to commercially pure titanium. The TiB nanowhisker-reinforced TMC has good biocompatibility and shows excellent mechanical properties for biomedical implant applications.

Pediatric population health analysis of southern and central Illinois region: A cross sectional retrospective study using association rule mining and multiple logistic regression.

BACKGROUND: Southern Illinois University School of Medicine (SIUSOM) collects large amounts of data every day. SIUSOM and other similar healthcare systems are always looking for better ways to use the data to understand and address population level problems. The purpose of this study is to analyze the administrative dataset for pediatric patients served by Southern Illinois University School of Medicine (SIUSOM) to uncover patterns that correlate specific demographic information to diagnoses of pediatric diseases. The study uses a cross-sectional database of medical billing information for all pediatric patients served by SIUSOM between June 2013 and December 2016. The dataset consists of about 980.9K clinical visits for 65.4K unique patients and includes patient demographic identifiers such as their sex, date of birth, race, anonymous zipcode and primary and secondary insurance plan as well as the related pediatric diagnosis codes. The goal is to find unknown correlations in this database. METHOD: We proposed a two step methodology to derive unknown correlations in SIUSOM administrative database. First, Class association rule mining was used as a well-established data mining method to generate hypothesis and derive associations of the form D → M, where D is diagnosis code of a pediatric disease and M is a patient demographic identifier (age,sex, anonymous zipcode, insurance plan, or race). The resulting associations were pruned and filtered using measures such as lift, odds ratio, relative risk, and confidence. The final associations were selected by a pediatric doctor based on their clinical significance. Second,each association rule in the final set was further validated and adjusted odds ratios were obtained using multiple logistic regression. RESULTS: Several associations were found correlating specific patients' residential zip codes with the diagnosis codes for viral hepatitis carrier, exposure to communicable diseases, screening for mental and developmental disorder in childhood, history allergy to medications, disturbance of emotions specific to childhood, and acute sinusitis. In addition, the results show that African American patients are more likely to be screened for mental and developmental disorders compared to White patients for SIUSOM pediatric population (Odds Ratio (OR):3.56, 95% Confidence Interval (CI):[3.29,3.85]). CONCLUSION: Class association rule mining is an effective method for detecting signals in a large patient administrative database and generating hypotheses which correlate patients' demographics with diagnosis of pediatric diseases. A post processing of the hypotheses generated by this method is necessary to prune spurious associations and select a set of clinically relevant hypotheses.

Deformation behavior of porous PHBV scaffold in compression: A finite element analysis study.

Macroscopic mechanical properties of porous PHBV bone TE scaffolds have been well studied. However, their mechanical behavior at microscopic level has yet to be explored. In this study, the micro-mechanical behavior of a PHBV bone scaffold under compression was investigated using a numerical method that combines micro-computed tomography (µ-CT) and finite element analysis (FEA). It was found that the use of a linear-elastic model resulted in an overestimation of the stiffness of the scaffold, whereas a more realistic estimation of the scaffold's deformation behavior was obtained by utilizing a bilinear material model. The onset of plastic deformation occurred in the very early stage of loading resulting in significantly reduced stiffness of the scaffold. The non-uniform and arbitrary microstructure of the scaffold led to a heterogeneous stress distribution within the porous construct, which was subjected to a mixture of compressive and tensile stresses. Nevertheless, the resultant stress contours showed that the scaffold experienced primarily elastic deformation when it was loaded up to 0.003 strain, while localized plastic deformation occurred at sharp corners and necked regions of the micro-struts. The scaffold expanded slightly in the horizontal direction as it was compressed and the change in geometries of pores within the scaffold was insignificant. The proposed method provides a valuable tool to study the localized mechanical behavior of bone scaffolds in micrometer scale with arbitrary porous architecture. This approach could prove highly useful for guiding the fabrication of scaffolds that have anatomy specific mechanical properties and porous architecture.

Secreted metalloproteases ADAMTS9 and ADAMTS20 have a non-canonical role in ciliary vesicle growth during ciliogenesis.

Although hundreds of cytosolic or transmembrane molecules form the primary cilium, few secreted molecules are known to contribute to ciliogenesis. Here, homologous secreted metalloproteases ADAMTS9 and ADAMTS20 are identified as ciliogenesis regulators that act intracellularly. Secreted and furin-processed ADAMTS9 bound heparan sulfate and was internalized by LRP1, LRP2 and clathrin-mediated endocytosis to be gathered in Rab11 vesicles with a unique periciliary localization defined by super-resolution microscopy. CRISPR-Cas9 inactivation of ADAMTS9 impaired ciliogenesis in RPE-1 cells, which was restored by catalytically active ADAMTS9 or ADAMTS20 acting in trans, but not by their proteolytically inactive mutants. Their mutagenesis in mice impaired neural and yolk sac ciliogenesis, leading to morphogenetic anomalies resulting from impaired hedgehog signaling, which is transduced by primary cilia. In addition to their cognate extracellular proteolytic activity, ADAMTS9 and ADAMTS20 thus have an additional proteolytic role intracellularly, revealing an unexpected regulatory dimension in ciliogenesis.