One-step Approaches Research Articles

Classification based on extensions of LS-PLS using logistic regression: application to clinical and multiple genomic data

BackgroundTo address high-dimensional genomic data, most of the proposed prediction methods make use of genomic data alone without considering clinical data, which are often available and known to have predictive value. Recent studies suggest that combining clinical and genomic information may improve predictions. We consider here methods for classification purposes that simultaneously use both types of variables but apply dimensionality reduction only to the high-dimensional genomic ones.ResultsUsing partial least squares (PLS), we propose some one-step approaches based on three extensions of the least squares (LS)-PLS method for logistic regression. A comparison of their prediction performances via a simulation and on real data sets from cancer studies is conducted.ConclusionIn general, those methods using only clinical data or only genomic data perform poorly. The advantage of using LS-PLS methods for classification and their performances are shown and then used to analyze clinical and genomic data. The corresponding prediction results are encouraging and stable regardless of the data set and/or number of selected features. These extensions have been implemented in the R package lsplsGlm to enhance their use.

One-step versus two-step diagnostic testing for gestational diabetes: a randomized controlled trial

Objective: To evaluate the incidence of gestational diabetes mellitus (GDM) using the one-step as compared with the two-step approach.Study design: This was a parallel group nonblinded randomized trial conducted at Thomas Jefferson University Hospital (TJUH) in Philadelphia, Pennsylvania from June 2016 to December 2016. The primary outcome was GDM incidence in the one-step compared to the two-approach. Pregnant women without a history of pregestational diabetes were offered screening for GDM at gestational age 24–28 weeks. Obese women, defined as having a BMI ≥30 kg/m2, as well as those with a history of a pregnancy complicated by GDM, a history of a macrosomic baby (>4000 g), or with polycystic ovarian syndrome (PCOS), were offered early screening at their initial prenatal visit, and screening was repeated at 24–28 weeks if initially normal. Women were excluded if they had pre-existing diabetes or had a history of bariatric surgery. Women who were eligible were randomized in a 1:1 ratio to either the one-step or two-step approaches. A sample size of 142 women was planned per group. Women randomized to the one-step approach, after an overnight fast, were given a 2-h glucose tolerance test, which consisted of a 75-g glucose load. Blood glucose levels were measured fasting, at 1 h and 2 h after the glucose load. Diagnostic cutoffs for GDM diagnosis were one value of either fasting ≥92 mg/dL, 1 h ≥180 mg/dL, or 2 h ≥153 mg/dL, respectively. Women randomized to the two-step approach were given a nonfasting 50-g glucose load, and the blood glucose level was measured an hour after the glucose load. If that value was ≥135 mg/dL, the patient had a 3-h glucose tolerance test consisting of a 100-g glucose load. Diagnostic cutoffs for GDM diagnosis for this 3-h test were ≥2 abnormal values of fasting ≥95 mg/dL, 1 h ≥180 mg/dL, 2 h ≥155 mg/dL and 3 h ≥140 mg/dL, respectively. All analyses were done using an intention-to-treat approach, evaluating women according to the treatment group to which they were randomly allocated.Results: Two hundred eighty-four women agreed to take part in the study and underwent randomization from June 2015 to December 2015. Of them, 249 completed the screening and were followed up for the primary endpoint. Out of the 249 women who completed the screening, 123 were assigned to the one-step group and 126 to the two-step group. GDM occurred in 10 women (8.1%) in the one-step group, and 7 women (5.6%) in the two-step group (p = .42). Preeclampsia, preterm birth (PTB), induction of labor, mode of delivery and incidence of gestational age (OASIS) were not significantly different. Perinatal outcomes were similar as well.Conclusions: Screening for GDM with one-step, compared with the two-step approach, resulted in a similar incidence of GDM.

Incidence, risk factors, and pregnancy outcomes of gestational diabetes mellitus using one-step versus two-step diagnostic approaches: A population-based cohort study in Isfahan, Iran

AimsTo study the incidence, risk factors, and pregnancy outcomes associated with gestational diabetes mellitus (GDM) diagnosed with one-step and two-step screening approaches. Methods1000 pregnant women who were eligible and consented to participate underwent fasting plasma glucose testing at the first prenatal visit (6–14 weeks). The women free from GDM or overt diabetes were screened at 24–28 weeks using the 50-g glucose challenge test (GCT) followed by 100-g, 3-h oral glucose tolerance test (OGTT) (two-step method). Regardless of the GCT result, all women underwent a 75-g, 2-h OGTT within one-week interval (one-step method). ResultsGDM incidence using the one-step and two-step methods was 9.3% (95% CI: 7.4–11.2) and 4.2% (95% CI: 2.9–5.5). GDM significantly increased the risk of macrosomia, gestational hypertension, preeclampsia, and cesarean section and older age and family history of diabetes significantly increased the risk of developing GDM in both approaches. In two-step method, higher pre-pregnancy body mass index and lower physical activity during pregnancy along with higher earlier cesarean section also increased significantly the risk of developing GDM. ConclusionsDespite a higher incidence of GDM using the one-step approach, more risk factors for and a stronger effect of GDM on adverse pregnancy outcomes were found when using the two-step approach. Longer follow-up of women with and without GDM may change the results using both approaches.

A Comparison of One-Step and Three-Step Approaches for Including Covariates in the Shared Parameter Growth Mixture Model

The shared parameter growth mixture model (SPGMM) has been proposed as a method to handle missing not at random (MNAR) data in longitudinal studies. This Monte Carlo simulation study compared the one-step approach with a three-step approach for adding covariates into the SPGMM. The results showed that performances of one-step and three-step approaches did not differ, but the estimate of the coefficient of the covariate was biased in most conditions with MNAR data. However, means, variances, and covariance of the intercept and slope as well as their standard errors were estimated without bias in most conditions, except for some combinations of small class distances and MNAR dropout missingness that was not related to the underlying growth trajectory. Classification accuracy was similar with both one-step and three-step SPGMM.

The efficiency of several one-step testing strategies for the diagnosis of hepatitis C.

implementing one-step strategies for hepatitis C diagnosis would help shorten the time to treatment access. Thus avoiding disease progression and complications, while facilitating hepatitis C virus (HCV) elimination. to assess the validity and certainty of potential one-step strategies for the diagnosis of HCV infection and their associated cost and efficiency. the study design is an economic appraisal of efficiency (cost/efficacy) using decision trees and deterministic sensitivity analysis. The analysis was performed from the payer perspective (Spanish National Health System), which exclusively considers the direct costs. Only the differential costs (diagnostic testing costs) were taken into account and the study was set in Spain. The efficacy of a diagnostic strategy was defined as the percentage of patients with an active HCV infection who received a positive diagnosis and the efficiency was defined as the cost per patient with a correctly diagnosed and active infection. the one-step strategies evaluated for the diagnosis of HCV had an acceptable validity and certainty due to the high sensitivity and specificity of the considered tests. The Ab-Ag strategy was the most efficient, followed by Ab-Ag-VL and Ab-VL. Ab-Ag was the most efficient due to the lower cost per patient tested, although the efficacy was lower than the Ab-VL efficacy. the study findings may help to establish more appropriate one-step diagnostic approaches whilst considering the efficacy and efficiency.

A comparative study of one-step and two-step approaches for MAPbI3 perovskite layer and its influence on the performance of mesoscopic perovskite solar cell

The mesoscopic perovskite solar cells (M-PSCs) were synthesized with MAPbI3 perovskite layers as light harvesters, which were grown with one-step and two-step solution process, respectively. A comparative study was performed through the quantitative correlation of resulting device performance and the crystalline quality of perovskite layers. Comparing with the one-step counterpart, a pronounced improvement in the steady-state power conversion efficiencies (PCEs) by 56.86% was achieved with two-step process, which was mainly resulted from the significant enhancement in fill factor (FF) from 48% to 77% without sacrificing the open circuit voltage (Voc) and short circuit current (Jsc). The enhanced FF was attributed to the reduced non-radiative recombination channels due to the better crystalline quality and larger grain size with the two-step processed perovskite layer. Moreover, the superiority of two-step over one-step process was demonstrated with rather good reproducibility.

Centralized and decentralized utilization of organic residues for lactic acid production

Depending on the source, the composition of organic waste can be heterogeneous. A mixture of organic waste and food waste appearing in urban areas was estimated to contain in average 550 kg t−1 carbohydrates (including 400 kg t−1 starch), 119.1 kg t−1 lipids and 54 kg t−1 proteins. Contrarily, the organic waste produced by fruits and vegetables processing industry is predictable in quality and quantity. This study considers the production of lactic acid from waste organic material using one-step or two-step approaches. One-step approaches are based on simultaneous hydrolysis and fermentation, while in two-step approaches both are carried out sequentially. It is recommended to implement one-step and two-step processes for an on- and off-site utilization of organic waste, respectively. The scenarios sketched are based on organic waste produced by hotels and in urban areas, and organic waste produced by fruits and vegetables processing industries. It is argued that a decentralized one-step process is appropriate at locations, such as food and vegetables processing industries, where sufficient organic waste is formed and interest in using the bio-based products exists. While two-step processes are to implement at locations where organic and inorganic waste streams are mixed and quality and quantity vary. It is further argued that a decentralized utilization may not end with a final product, but with an easy transportable solution containing either convertible nutrients or the lactic acid containing fermentation broth serving as feedstock to relevant industries. The sketched scenarios are not limited to lactic acid, but can be considered for other biobased products whose production contributes to sustainability and bioeconomy.

Results Of Individual Participant Data Meta-Analysis VS Aggregate Data Meta-Analysis Of RCTS Of Exercise Rehabilitation In Chronic Heart Failure

Traditional meta-analyses synthesise aggregate data obtained from study publications or study authors, such as a treatment effect estimate and its associated uncertainty. An increasingly popular approach is the meta-analysis of individual participant data (IPD) where the raw individual-level data are obtained for each study and used for synthesis. This study compares and discusses results from an IPD meta-analysis vs standard meta-analysis of randomized controlled trials of exercise cardiac rehabilitation in chronic heart failure (CHF). Based on a previous systematic review, the Exercise Training Meta-Analysis of Trials for Chronic Heart Failure (ExTraMATCH II) identified and collected IPD from RCTs that compared exercise rehabilitation with a non-exercise control and a minimum follow-up of 6 months. Outcomes of interest were mortality, hospitalization, exercise capacity and health-related quality of life. Original IPD were checked for consistency and compiled in a master dataset. Standard meta-analytic models were used for aggregate data whilst one-step approaches accounting for the clustering of participants within studies were planned for statistical analyses of IPD. Overall 33 RCTs were included in the original systematic review, whereas within the ExTraMatch II project, IPD were obtained from 19 RCTs in approximately 4,000 patients. From aggregate data there was no significant difference in pooled mortality (RR 0.92, 95%CI 0.67 to 1.26), whereas there was an effect of exercise rehabilitation on hospitalization (RR 0.75, 95% CI 0.62 to 0.92) and health related quality of life (SMD −0.46, 95% CI −0.66 to −0.26). IPD analysis is currently underway; the results will allow examining how patients’ characteristics modify treatment benefit. Given the limitations of current evidence in CHF, access to individual data from several RCTs offers a timely and important opportunity to revisit the question of which CHF patient subgroups benefit most from exercise-based rehabilitation.

Sonographic differentiation between lymphatic and metastatic diseases in cervical lymphadenopathy.

The spectrum of differential diagnosis in cervical lymphadenopathy is extremely broad. In lymphoma and inflammatory diseases, surgical approaches are restricted to diagnostic lymph extirpation, whereas metastatic outgrowth into regional lymph nodes usually requires neck dissection. Lymph node surgery has to manage the balancing act between sufficient radicality and preservation of functional structures. The current study, therefore, aimed to identify parameters to differentiate between lymph nodes of lymphatic and metastatic origin. Single-center, retrospective cohort study. Clinical and sonographic parameters from all patients who underwent diagnostic cervical lymphadenectomy from 2010 to 2015 (N = 262) were included in this retrospective analysis. Parameters with significant differences between the two subgroups were utilized to create a clinical algorithm to distinguish between cervical lymphadenopathy of lymphatic and metastatic genesis. Statistically significant differences between the two subgroups could be shown for clinical (gender, age, nicotine/alcohol abuse, B symptoms, history of cutaneous melanoma, or lymphoma) and ultrasonographic parameters (string-of-beads confirmation, bilaterality, homogenous echostructure, localization in level I, long-to-short axis ratio, and hilar vascularity). The proposed algorithm yielded a sensitivity of 92.4% for metastatic disease. The implemented algorithm based on ultrasonographic and clinical criteria contributes to one-step surgical approaches that guarantee a sufficient radicality with a minimum of functional loss. 4. Laryngoscope, 128:859-863, 2018.

Design of ultra-lightweight and high-strength cellular structural composites inspired by biomimetics

Abstract Cellular composites are of significant interest to the materials research community as they often possess multifunctional physical properties. To meet the application requirements, various design and fabrication methods are adopted to produce highly porous composites. In this work, the one-step and two-step approaches for efficient design and prediction of cellular structure's performance were presented for developing ultra-lightweight and high-strength cellular composites reinforced by discontinuous fibers. The topology designs of a 2D honeycomb hexagon model, a 2D cuttlefish model, and a 3D octahedron model, inspired by biomimetics, were presented. Computer modeling based on finite element analysis was conducted on the periodic representative volume elements identified from the cellular structural models to characterize the designed cellular composites' performance and properties. Additive manufacturing technique (3D printing) was used for prototyping the design, and experimental tests were carried out for validating the design methodology.

Microwave energy assisted carbonization of nanostructured conducting polymers for their potential use in energy storage applications

Abstract Three well-established one-step approaches, namely, conducting polymer (CP) nanofiber (NF) synthesis by NF seeding, CP nanoclip (NC) synthesis by oxidative template, and microwave (MW) energy-assisted carbonization were systematically combined to prepare carbonaceous nanostructures from CPs, with great potential as the active material for energy storage purposes. Polypyrrole (PPy), as one of the most well-known and commonly studied members of the CP family was prepared in both NF and NC forms, as the sacrificial carbonization precursor, for different property comparison purposes. Due to conducting polymers’ high electron mobility and easily exciting nature under MW irradiation, both PPy NF and NC samples had vigorously interacted with MWs. The as-obtained carbonaceous samples from such interactions exhibited high thermal stabilities, competitive specific capacitance values and long-term stable electrochemical cyclic performances, which are crucial for the active materials used in energy storage applications. Thus, it is believed that, this well-established and well-studied process combination will dominate the large-scale manufacturing of the carbon-based, active energy storage materials from CPs.

An easy and efficient inducible CRISPR/Cas9 platform with improved specificity for multiple gene targeting.

The CRISPR/Cas9 system is a powerful genome editing tool and has been widely used for biomedical research. However, many challenges, such as off-target effects and lack of easy solutions for multiplex targeting, are still limiting its applications. To overcome these challenges, we first developed a highly efficient doxycycline-inducible Cas9-EGFP vector. This vector allowed us to track the cells for uniform temporal control and efficient gene disruption, even in a polyclonal setting. Furthermore, the inducible CRISPR/Cas9 system dramatically decreased off-target effects with a pulse exposure of the genome to the Cas9/sgRNA complex. To target multiple genes simultaneously, we established simple one-step cloning approaches for expression of multiple sgRNAs with improved vectors. By combining our inducible and multiplex genome editing approaches, we were able to simultaneously delete Lysine Demethylase (KDM) 5A, 5B and 5C efficiently in vitro and in vivo. This user friendly and highly efficient toolbox provides a solution for easy genome editing with tight temporal control, minimal off-target effects and multiplex targeting.

Confirmatory Factor Analysis Compared with Principal Component Analysis to Derive Dietary Patterns: A Longitudinal Study in Adult Women1–3

Background: Principal component analysis (PCA) has been used extensively to derive dietary patterns. We proposed to use confirmatory factor analysis (CFA) in the same context as PCA—as a one-step approach—to derive dietary patterns.Objectives: The first aim of this study was methodologic and was to compare dietary patterns derived with the use of PCA and CFA, used as equivalent one-step approaches. The second aim of this study was to study these patterns in association with individual characteristics and new adult-onset asthma.Methods: We included 30,589 French women from the E3N (epidemiologic prospective cohort study of women from the MGEN national insurance plan) with 1177 reported cases of adult-onset asthma between 1993 and 2005. PCA and CFA were used in the same context, on 27 food groups, to derive dietary patterns. Associations between dietary patterns and adult-onset asthma were assessed by Cox proportional hazards models.Results: Whether we used PCA or CFA, 3 similar factors were found and labeled “Prudent,” “Western,” and “Aperitif.” Correlations between patterns derived with the use of PCA and CFA were high. For the “Prudent” and “Aperitif” patterns, we observed comparable patterns in terms of associations with food groups, individual characteristics, and the onset of asthma. For the “Western” patterns, the one derived with the use of CFA was more related to an unhealthy diet than the one derived with the use of PCA, with higher correlations with the food groups “processed meat” (0.73 vs. 0.51) and “dough and pastry” (0.63 vs. 0.40), and negative associations with physical activity and with having parents who were farmers. Regarding associations with adult-onset asthma, a significant positive association was observed for the “Western” pattern derived with the use of CFA [multivariate RR for highest vs. lowest quintile: 1.30 (1.02, 1.67), P-trend: 0.03], whereas no association was reported when using PCA [RR: 1.14 (0.89, 1.47), P-trend: 0.40].Conclusion: Although quite similar dietary patterns were derived with the use of PCA and CFA, this study supports the alternative use of CFA to PCA for the identification of dietary patterns in epidemiologic studies.

Effects of IGF-I overexpression on the chondrogenic potential of human bone marrow aspirates modified via rAAV gene transfer

Purpose: The use of genetically modified bone marrow aspirates may provide convenient, one-step therapeutic approaches to regenerate injured articular cartilage. Here, we examined the effects of overexpressing the mitogenic and pro-anabolic IGF-I factor via the potent and safe rAAV gene transfer vectors on the reparative activities of human osteoarthritic bone marrow aspirates. Methods: Bone marrow aspirates were obtained from the distal femurs of osteoarthritic patients undergoing total knee arthroplasty. All patients provided informed consent before inclusion in the study. rAAV vectors were prepared according to a routine protocol using the candidate rAAV-hIGF-I versus control (reporter) rAAV-lacZ constructs. Aspirates were transduced with each vector and maintained in chondrogenic culture condition for 21 days. Transgene expression was monitored by immunohistochemistry on paraffin-embedded sections of aspirates that were also stained with toluidine blue and for immunodetection of type-II collagen. The DNA and proteoglycan contents were monitored by Hoechst 22358 assay and binding to DMMB, respectively. Total RNA was extracted and reverse transcription was carried out for cDNA amplification via real-time RT-PCR. Ct values were obtained for SOX9, ACAN, COL2A1, COL1A1, and COL10A1, using GAPDH as a control for normalization, and fold inductions relative to luc-treated samples were measured using the 2-ΔΔCt method. Each condition was performed in duplicate in three experiments. The t-test was employed with P ≤ 0.05 considered statistically significant. Results: Effective IGF-I expression was noted in rAAV-hIGF-I-treated aspirates vis-à-vis control (rAAV-lacZ) condition. Enhanced chondrogenic differentiation was observed in the aspirates after 21 days upon IGF-I gene transfer versus lacZ as seen by a more robust toluidine blue staining and stronger type-II collagen immunoreactivity. The candidate IGF-I treatment also significantly increased the DNA and proteoglycan contents in the aspirates. These findings were corroborated at the gene expression level by a real-time RT-PCR analysis of SOX9, ACAN, and COL2A1. Of further note, IGF-I gene transfer also increased the expression of hypertrophic markers (COL1A1, COL10A1). Conclusions: rAAV vectors can successfully modify human osteoarthritic bone marrow aspirates to overexpress IGF-I, leading to enhanced metabolic and chondrogenic differentiation activities relative to control treatment. Regulating IGF-I production will be necessary for a tight control of terminal differentiation and hypertrophy before adapting the present strategy to treat damaged articular cartilage.

ChemInform Abstract: Recent Advances in Organocatalytic Asymmetric Synthesis of Polysubstituted Pyrrolidines

AbstractReview: [44 refs.

Enhanced cell adhesion on silk fibroin via lectin surface modification

Various tissue engineering (TE) approaches are based on silk fibroin (SF) as scaffold material because of its superior mechanical and biological properties compared to other materials. The translation of one-step TE approaches to clinical application has generally failed so far due to the requirement of a prolonged cell seeding step before implantation. Here, we propose that the plant lectin WGA (wheat germ agglutinin), covalently bound to SF, will mediate cell adhesion in a time frame acceptable to be part of a one-step surgical intervention. After the establishment of a modification protocol utilizing carbodiimide chemistry, we examined the attachment of cells, with a special focus on adipose-derived stromal cells (ASC), on WGA-SF compared to pure native SF. After a limited time frame of 20min the attachment of ASCs to WGA-SF showed an increase of about 17-fold, as compared to pure native SF. The lectin-mediated cell adhesion further showed an enhanced resistance to trypsin (as a protease model) and to applied fluid shear stress (mechanical stability). Moreover, we could demonstrate that the adhesion of ASCs on the WGA-SF does not negatively influence proliferation or differentiation potential into the osteogenic lineage. To test for in vitro immune response, the proliferation of peripheral blood mononuclear cells in contact with the WGA-SF was determined, showing no alterations compared to plain SF. All these findings suggest that the WGA modification of SF offers important benefits for translation of SF scaffolds into clinical applications.

Characterization of Real Eigenvalues in Linear Viscoelastic Oscillators and the Nonviscous Set

In structural dynamics, energy dissipative mechanisms with nonviscous damping are characterized by their dependence on the time-history of the response velocity, which is mathematically represented by convolution integrals involving hereditary functions. The widespread Biot damping model assumes that such functions are exponential kernels, which modify the eigenvalues' set so that as many real eigenvalues (named nonviscous eigenvalues) as kernels are added to the system. This paper is focused on the study of a mathematical characterization of the nonviscous eigenvalues. The theoretical results allow the bounding of a set belonging to the real negative numbers, called the nonviscous set, constructed as the union of closed intervals. Exact analytical solutions of the nonviscous set for one and two exponential kernels and approximated solutions for the general case of N kernels are developed. In addition, the nonviscous set is used to build closed-form expressions to compute the nonviscous eigenvalues. The results are validated with numerical examples covering single and multiple degree-of-freedom systems where the proposed method is compared with other existing one-step approaches available in the literature.

English

Introduction This article reviews the evolution of cartilage regeneration therapeutic approaches from two-step cell-based autologous chondrocyte implantation procedures to current one-step cell-free scaffold-assisted cartilage repair approaches for chondral cartilage repair. In particular, our research is focused on clinical data about commercially available cell-free implants used in regenerative medicine approaches for the treatment of chondral cartilage defects. Discussion Chondral cartilage lesions do not heal spontaneously and may progress to severe osteoarthritis. For cartilage repair, a variety of surgical techniques have been established over the years. Further research led to the development of current new one-step cell-free scaffold-assisted cartilage repair approaches based on the experience with scaffold materials in previous two-step autologous chondrocyte implantation procedures. Commercially available scaffold-based products for one-step chondral cartilage repair have been recently tested in first case series and showed promising clinical outcome in the short-term follow-up; however, medium- and long-term comparative studies are necessary to evaluate the regenerative potential of this new one-step cartilage repair procedure and to demonstrate its superiority over or adequacy to traditional approaches. Conclusion This critical review summarises the development from two-step cell-based autologous chondrocyte implantation procedures to new onestep cell-free cartilage repair and discusses the first clinical outcome of commercially available cell-free implants. This new approach, based on the principle of cell ingrowths and guidance towards tissue repair, showed promising first clinical results and is considered as an effective and safe treatment option for chondral cartilage repair.

Polyglycolic acid-hyaluronan scaffolds loaded with bone marrow-derived mesenchymal stem cells show chondrogenic differentiationin vitroand cartilage repair in the rabbit model

In cartilage repair, scaffold-assisted one-step approaches are used to improve the microfracture (Mfx) technique. Since the number of progenitors in Mfx is low and may further decrease with age, aim of our study was to analyze the chondrogenic potential of freeze-dried polyglycolic acid-hyaluronan (PGA-HA) implants preloaded with mesenchymal stem cells (MSCs) in vitro and in a rabbit articular cartilage defect model. Human bone marrow-derived MSC from iliac crest were cultured in freeze-dried PGA-HA implants for chondrogenic differentiation. In a pilot study, implants were loaded with autologous rabbit MSC and used to cover 5 mm × 6 mm full-thickness femoral articular cartilage defects (n = 4). Untreated defects (n = 3) served as controls. Gene expression analysis and histology showed induction of typical chondrogenic marker genes like type II collagen and formation of hyaline-like cartilaginous tissue in MSC-laden PGA-HA implants. Histological evaluation of rabbit repair tissue formation after 30 and 45 days showed formation of repair tissue, rich in chondrocytic cells and of a hyaline-like appearance. Controls showed no articular resurfacing, tissue repair in the subchondral zone and fibrin formation. These results suggest that MSC-laden PGA-HA scaffolds have chondrogenic potential and are a promising option for stem cell-mediated cartilage regeneration.

Shedding Light on Vacancy-Doped Copper Chalcogenides: Shape-Controlled Synthesis, Optical Properties, and Modeling of Copper Telluride Nanocrystals with Near-Infrared Plasmon Resonances

Size- and shape-controlled synthesis of copper chalcogenide nanocrystals (NCs) is of paramount importance for a careful engineering and understanding of their optoelectronic properties and, thus, for their exploitation in energy- and plasmonic-related applications. From the copper chalcogenide family copper telluride NCs have remained fairly unexplored as a result of a poor size-, shape-, and monodispersity control that is achieved via one-step syntheses approaches. Here we show that copper telluride (namely Cu(2-x)Te) NCs with well-defined morphologies (spheres, rods, tetrapods) can be prepared via cation exchange of preformed CdTe NCs while retaining their original shape. The resulting copper telluride NCs are characterized by pronounced plasmon bands in the near-infrared (NIR), in analogy to other copper-deficient chalcogenides (Cu(2-x)S, Cu(2-x)Se). We demonstrate that the extinction spectra of the as-prepared NCs are in agreement with theoretical calculations based on the discrete dipole approximation and an empirical dielectric function for Cu(2-x)Te. Additionally we show that the Drude model does not appropriately describe the complete set of Cu(2-x)Te NCs with different shapes. In particular, the low-intensity longitudinal plasmon bands for nanorods and tetrapods are better described by a modified Drude model with an increased damping in the long-wavelength interval. Importantly, a Lorentz model of localized quantum oscillators describes reasonably well all three morphologies, suggesting that holes in the valence band of Cu(2-x)Te cannot be described as fully free particles and that the effects of localization of holes are important. A similar behavior for Cu2-xS and Cu(2-x)Se NCs suggests that the effect of localization of holes can be a common property for the whole class of copper chalcogenide NCs. Taken altogether, our results represent a simple route toward copper telluride nanocrystals with well-defined shapes and optical properties and extend the understanding on vacancy-doped copper chalcogenide NCs with NIR optical resonances.