Surface Functionalization with Polymer Brushes via Surface-Initiated Atom Transfer Radical Polymerization: Synthesis, Applications, and Current Challenges.

Polymer brushes have received great attention in recent years due to their distinctive properties and wide range of applications. The synthesis of polymer brushes typically employs surface-initiated atom transfer radical polymerization (SI-ATRP) techniques. To realize the control of the polymerization process in different environments, various SI-ATRP techniques triggered by different stimuli have been developed. This review focuses on the latest developments in different stimuli-triggered SI-ATRP methods, such as electrochemically mediated, photoinduced, enzyme-assisted, mechanically controlled, and organocatalyzed ATRP. Additionally, SI-ATRP technology triggered by a combination of multiple stimuli sources is also discussed. Furthermore, the applications of polymer brushes in lubrication, biological applications, antifouling, and catalysis are also systematically summarized and discussed. Despite the advancements in the synthesis of various types of 1D, 2D, and 3D polymer brushes via controlled radical polymerization, contemporary challenges remain in the quest for more efficient and straightforward synthetic protocols that allow for precise control over the composition, structure, and functionality of polymer brushes. We anticipate the readers could promote the understanding of surface functionalization based on ATRP-mediated polymer brushes and envision future directions for their application in surface coating technologies.

Treatment of Pauwels III femoral neck fracture in young patients using biplane double support screw internal fixation technology based on X-ray image.

Traditional treatment methods have certain limitations. In recent years, the technique of internal fixation with double-plane double-supported screws based on X-ray images has been proposed to improve the therapeutic effect. The main objective of this research was to examine the effectiveness of the X-ray image-based bi-planar double-braced screw internal fixation technique . During surgery, the procedure was determined based on X-ray images, followed by an open reduction procedure at the fracture site, and finally internal fixation using bi-planar double-support screws. All patients were successfully treated with X-ray image-based bi-planar double support screw fixation. After surgery, X-ray images showed a good reduction of the fracture site without significant loosening or failure of the internal fixation. At the postoperative follow-up, the patient's pain symptoms were significantly relieved, and no significant complications occurred during recovery.

Electrochemically Mediated Surface-Initiated Atom Transfer Radical Polymerization by ppm of CuII/Tris(2-pyridylmethyl)amine.

Atom transfer radical polymerization (ATRP) is one of the most widely used methods for modifying surfaces with functional polymer films and has received considerable attention in recent years. Here, we report an electrochemically mediated surface-initiated ATRP to graft polymer brushes onto solid substrates catalyzed by ppm amounts of CuII/TPMA in water/MeOH solution. We systematically investigated the type and concentrations of copper/ligand and applied potentials correlated to the polymerization kinetics and polymer brush thickness. Gradient polymer brushes and various types of polymer brushes are prepared. Block copolymerization of 2-hydroxyethyl methacrylate (HEMA) and 3-sulfopropyl methacrylate potassium salt (PSPMA) (poly(HEMA-b-SPMA)) with ultralow ppm eATRP indicates the remarkable preservation of chain end functionality and a pronounced "living" characteristic feature of ppm-level eATRP in aqueous solution for surface polymerization.

Development and validation of machine learning models for venous thromboembolism risk assessment at admission: a retrospective study.

Introduction: Venous thromboembolism (VTE) risk assessment at admission is of great importance for early screening and timely prophylaxis and management during hospitalization. The purpose of this study is to develop and validate novel risk assessment models at admission based on machine learning (ML) methods. Methods: In this retrospective study, a total of 3078 individuals were included with their Caprini variables within 24 hours at admission. Then several ML models were built, including logistic regression (LR), random forest (RF), and extreme gradient boosting (XGB). The prediction performance of ML models and the Caprini risk score (CRS) was then validated and compared through a series of evaluation metrics. Results: The values of AUROC and AUPRC were 0.798 and 0.303 for LR, 0.804 and 0.360 for RF, and 0.796 and 0.352 for XGB, respectively, which outperformed CRS significantly (0.714 and 0.180, P < 0.001). When prediction scores were stratified into three risk levels for application, RF could obtain more reasonable results than CRS, including smaller false positive alerts and larger lower-risk proportions. The boosting results of stratification were further verified by the net-reclassification-improvement (NRI) analysis. Discussion: This study indicated that machine learning models could improve VTE risk prediction at admission compared with CRS. Among the ML models, RF was found to have superior performance and great potential in clinical practice.

Oxygen-Tolerant Photografting for Surface Structuring from Microliter Volumes.

Here, we report an oxygen-tolerant photografting technique to grow polymer brushes employing microliter volumes of monomer solution under ambient conditions. With the key advantages that include spatial control, initiator/catalyst-free nature, and high oxygen tolerance, a series of homo-, multiblock, and arbitrary patterned polymer brushes were successfully obtained by photografting. Moreover, a dual-functional surface with hydrophilic and hydrophobic properties could easily be realized by one-pot photografting. These results illustrated the practicality and versatility of this strategy, which will allow nonexperts access to polymer brush architectures and broaden the potential applications of polymer brushes.

A Strong and Double-sided Self-Adhesive Hydrogel Sensor.

Flexible self-adhesive hydrogel sensors are attracting considerable concerns in recent years. However, creating a self-adhesive hydrogel sensor with excellent mechanical properties remains to be challenging. Herein, a double-sided self-adhesive hydrogel capable of strain sensor with high strength is demonstrated by penetration strategy. The middle poly(acrylic acid)-polyacrylamide/Fe3+ (PAA-PAM/Fe3+ ) tough layer endows the double-sided self-adhesive hydrogel with high mechanical properties, while the bilateral poly[2-(methacryloyloxy) ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide-polyacrylamide (PSBMA-PAM) adhesive layers are used to ensure excellent adhesiveness on diverse substrates. The tough layer of the double-sided self-adhesive hydrogel sensor shows a strong interface bonding force against the adhesive layer. The double-sided self-adhesive hydrogel sensor enables excellent adhesiveness on diverse substrates. More importantly, it can accurately detect different strains and human motions as a self-adhesive hydrogel strain sensor. This work manifests a new route of structural design to develop a self-adhesive hydrogel sensor with excellent mechanical properties that is suitable for a wide range of applications.

In Situ Surface-Initiated ATRP Mediated by Gallium-Based Liquid Metal Nanodroplets.

Surface-initiated atom transfer radical polymerization (SI-ATRP) is one of the most popular methods for surface modifications with functional polymer films, which has attracted significant attention in recent years. Herein, a facile method of gallium-based liquid metal (GLM) nanodroplets mediated SI-ATRP to prepare polymer brushes on GLM surfaces is reported. The ATRP initiator modified GLM (GLM-Br) nanodroplets act as a substrate for the in situ SI-ATRP and participate as a reducing agent to reduce Cu(II) deactivators to Cu(I) activators. UV-vis spectra confirm the feasibility of the in situ SI-ATRP and indicate that the thickness and density of polymer brushes play an important role in performing a successful ATRP on GLM nanodroplets surfaces. Homo- and block copolymers, poly(3-sulfopropyl methacrylate potassium salt) (PSPMA) and poly((2-dimethylamino)ethyl methacrylate-b-(3-sulfopropyl methacrylate potassium salt)) P(DMAEMA-b-SPMA) are successfully grafted to the GLM nanodroplets. Polymer brushes modified GLM nanodroplets show potential applications such as friction reduction and oil-water emulsion separation. GLM nanodroplets mediated SI-ATRP provides a novel and robust approach to preparing multifunctional GLM nanodroplets for different applications.

Molecular Plasmonic Silver Forests for the Photocatalytic-Driven Sensing Platforms.

Structural electronics, as well as flexible and wearable devices are applications that are possible by merging polymers with metal nanoparticles. However, using conventional technologies, it is challenging to fabricate plasmonic structures that remain flexible. We developed three-dimensional (3D) plasmonic nanostructures/polymer sensors via single-step laser processing and further functionalization with 4-nitrobenzenethiol (4-NBT) as a molecular probe. These sensors allow ultrasensitive detection with surface-enhanced Raman spectroscopy (SERS). We tracked the 4-NBT plasmonic enhancement and changes in its vibrational spectrum under the chemical environment perturbations. As a model system, we investigated the sensor's performance when exposed to prostate cancer cells' media over 7 days showing the possibility of identifying the cell death reflected in the environment through the effects on the 4-NBT probe. Thus, the fabricated sensor could have an impact on the monitoring of the cancer treatment process. Moreover, the laser-driven nanoparticles/polymer intermixing resulted in a free-form electrically conductive composite that withstands over 1000 bending cycles without losing electrical properties. Our results bridge the gap between plasmonic sensing with SERS and flexible electronics in a scalable, energy-efficient, inexpensive, and environmentally friendly way.

Driving Polymer Brushes from Synthesis to Functioning.

The great success of controlled radical polymerizations has encouraged researchers to develop more facile and robust approaches for surface-initiated polymerizations (SIPs) to fabricate polymer brushes, even for non-experts. In recent years, external-stimuli-mediated radical polymerization methods have come to the fore as SIPs because of their less rigorous synthetic procedures and high controllability, which expand the opportunities for synthesizing macromolecules with desired chemical compositions and structures, as well as tailor-made polymers and bioconjugates that show broad applicability and physiological compatibility. This review discusses the latest developments in surface-initiated polymerization methods, in particular, external-stimuli mediated atom transfer radical polymerization (ATRP), photo-induced polymerizations, and reversible addition-fragmentation chain transfer (RAFT) polymerization, as well as other methods and their combination for the application in surface grafting. The implementation of these methods is of great interest due to their unique possibilities to temporally control a polymerization process, fast and straightforward polymerization, and environmentally benign features, which lead to established and emerging applications in biolubrication, antifouling, and biosensing.

Hidden blood loss between percutaneous pedicle screw fixation and the mini-open Wiltse approach with pedicle screw fixation for neurologically intact thoracolumbar fractures: a retrospective study.

BACKGROUND: The aim of this study was to determine the proportion of hidden blood loss (HBL) in patients treated with minimally invasive surgery, and to compare the HBL between patients treated with percutaneous pedicle screw fixation (PPSF) and the mini-open Wiltse approach with pedicle screw fixation (MWPSF). METHODS: From January 2017 to January 2019, a total of 119 patients with thoracolumbar fractures were included in the analysis, of which 58 cases received PPSF and 61 cases received MWPSF. The clinical information and demographic results were collected and compared. And the HBL of the patients is calculated by the combination formulas of Nadler, Gross and Sehat. RESULTS: Compared with the PPSF group, operation time of MWPSF is shorter. The fluoroscopy times are 13.6 ± 3.0 in PPSF group and 5.6 ± 1.6 in MWPSF group (p < 0.001). As shown in Table 3, the intraoperative blood loss in PPSF group is 31.9 ± 9.6 ml, which is significantly less than that in the MWPSF group (44.0 ± 14.9 ml). The HBL (445.7 ± 228.9 ml), and HBL% (91.2 ± 7.7%) of the PPSF group are significantly higher than that in the MWPSF group (P < 0.05). And the total blood loss (TBL) of the PPSF group (477.6 ± 228.8 ml) is also more than that in the MWPSF group (401.0 ± 171.3 ml). CONCLUSIONS: Our results suggest that in the minimally invasive surgical treatment of thoracolumbar fractures, the perioperative HBL is much higher than visible blood loss (VBL). Although PPSF has less intraoperative blood loss, it has higher TBL and HBL than those of MWPSF. Compared with MWPSF, we should pay more attention to the postoperative anemia status of patients with thoracolumbar fractures undergoing PPSF surgery.

Tunable Hierarchically Structured Meso-Macroporous Carbon Spheres from a Solvent-Mediated Polymerization-Induced Self-Assembly.

Herein, we report a versatile solvent-mediated polymerization-induced self-assembly (PISA) strategy to directly synthesize highly N-doped hierarchically porous structured carbon spheres with a tunable meso-macroporous configuration. The introduction of intermolecular hydrogen bonds is verified to enhance the interfacial interactions between block copolymers, oil droplets, and polyphenols. Moreover, the dominant hydrogen-bond-driven interactions can be systematically manipulated by selecting different cosolvent systems to generate diverse porous structures from the transformation of micellar and precursor co-assembly. Impressively, hierarchically structured meso-macroporous N-doped carbon spheres present simultaneously tunable sphere sizes and mesopores and macropores, ranging from 1.2 µm, 9/50 and 227 nm to 1.0 µm, 40, and 183 nm and 480, 24, and 95 nm. As a demonstration, dendritic-like N-doped hierarchically meso-macroporous carbon spheres manifest excellent enzyme-like activity, which is attributed to the continuous mass transport from the multiordered porosity. The current study provides a new platform for the synthesis of novel well-defined porous materials.

A gradient boosting tree model for multi-department venous thromboembolism risk assessment with imbalanced data.

Venous thromboembolism (VTE) is the world's third most common cause of vascular mortality and a serious complication from multiple departments. Risk assessment of VTE guides clinical intervention in time and is of great importance to in-hospital patients. Traditional VTE risk assessment methods based on scaling tools, which always require rules carefully designed by human experts, are difficult to apply to large-population scenarios since the manually designed rules are not guaranteed to be accurate to all populations. In contrast, with the development of the electronic health record (EHR) datasets, data-driven machine-learning-based risk assessment methods have proven superior predictability in many studies in recent years. This paper uses the gradient boosting tree model to study the VTE risk assessment problem with multi-department data. There exist two distinct characteristics of VTE data collected at the level of the entire hospital: its wide distribution and heterogeneity across multiple departments. To this end, we consider the prediction task over multiple departments as a multi-task learning process, and introduce the algorithm of a task-aware tree-based method TSGB to tackle the multi-task prediction problem. Although the introduction of multi-task learning improves overall across-department performance, we reveal the problem of task-wise performance decline while dealing with imbalanced VTE data volume. According to the analysis, we finally propose two variants of TSGB to alleviate the problems and further boost the prediction performance. Compared with state-of-the-art rule-based and multi-task tree-based methods, the experimental results show the proposed methods not only improve the overall across-department AUC performance effectively, but also ensure the improvement of performance over every single department prediction.

Successive Redox-Reaction-Triggered Interface Radical Polymerization for Growing Hydrogel Coatings on Diverse Substrates.

Growing lubricating hydrogel coatings in controllable manners on diverse material surfaces demonstrates promising applications. Here, a surface modification method is reported for in situ growing hydrogel coatings onto surfaces of diverse substrates in the absence of UV assistance. It is performed by decorating substrates with a universal mussel-inspired synthetic adhesive with catechol groups. Upon being immersed in reaction solution, these groups can assist substrate bonding and in situ capture and reduce Fe3+ into Fe2+ for decomposing S2 O8 2- into SO4 - ⋅ catalytically at the interface to initiate interface polymerization of monomers. As a result, hydrogel coatings with controllable thickness could be grown on surfaces of arbitrary substrates to change their surface characteristics regardless of materials size, category, geometry and transparency, implying considerable potential in surface engineering.

miR-148a-3p facilitates osteogenic differentiation of fibroblasts in ankylosing spondylitis by activating the Wnt pathway and targeting DKK1.

Ankylosing spondylitis (AS) is a chronic inflammatory form of arthritis. MicroRNAs (miRNAs) have been identified to serve as therapeutic targets in various inflammatory diseases. The aim of the present study was to determine the functional mechanism of miR-148a-3p on AS. Specimens were collected from AS patients and non-AS patients. Fibroblasts were delivered with the aid of miR-148a-3p inhibitor. Cell staining was performed to observe the morphological changes, calcified nodules, and mineralization degree. The binding sites of miR-148a-3p and DKK1 were predicted on the Starbase website and subsequently verified by means of dual-luciferase reporter assay. AS fibroblasts with silenced miR-148a-3p were transfected with si-DKK1. Levels of RUNX2 and Osteocalcin, DKK1 and Wnt1 protein and phosphorylation level of ß-catenin were detected by means of western blot analysis. Results of the present study denoted that AS upregulated miR-148a-3p in fibroblasts to exacerbate osteogenic differentiation, resulting in increased calcified nodules and mineralization degree. Silencing miR-148a-3p could reverse the upregulation of RUNX2 and Osteocalcin in AS fibroblasts and reduce the calcified nodules and mineralization degree. miR-148a-3p targeted DKK1. DKK1 knockdown averted the effect of silencing miR-148a-3p in AS fibroblasts. In addition, silencing miR-148a-3p reversed the upregulation of Wnt1 and ß-catenin proteins in AS fibroblasts. To conclude, miR-148a-3p exacerbated the osteogenic differentiation of AS fibroblasts by inhibiting DKK1 expression and activating the Wnt pathway.

Toward a Multifunctional Light-Driven Biomimetic Mudskipper-Like Robot for Various Application Scenarios.

The systematicness, flexibility, and complexity of natural biological organisms are a constant stream of inspiration for researchers. Therefore, mimicking the natural intelligence system to develop microrobotics has attracted broad interests. However, developing a multifunctional device for various application scenarios has great challenges. Herein, we present a bionic multifunctional actuation device─a light-driven mudskipper-like actuator that is composed of a porous silicone elastomer and graphene oxide. The actuator exhibits a reversible and well-integrated response to near-infrared (NIR) light due to the photothermal-induced contractile stress in the actuation film, which promotes generation of cyclical and rapid locomotion upon NIR light being switched on and off, such as bending in air and crawling in liquid. Furthermore, through rational device design and modulation of light, the mechanically versatile device can float and swim controllably following a predesigned route at the liquid/air interface. More interestingly, the actuator can jump from liquid medium to air with an extremely short response time (400 ms), a maximum speed of 2 m s-1, and a height of 14.3 cm under the stimulation of near-infrared light. The present work possesses great potential in the applications of bioinspired actuators in various fields, such as microrobots, sensors, and locomotion.

Comparison of outcome between percutaneous pedicle screw fixation and the Mini-Open Wiltse Approach with pedicle screw fixation for neurologically intact thoracolumbar fractures: A retrospective study.

BACKGROUND: The purpose of this study was to compare the outcome between percutaneous pedicle screw fixation (PPSF) and the mini-open Wiltse approach with pedicle screw fixation (MWPSF) for neurologically intact thoracolumbar fractures. METHODS: From January 2017 to January 2019, ninety-four patients with neurologically intact thoracolumbar fractures were included in this study. In this retrospective study, forty-nine patients were operated with the PPSF and forty-five patients received MWPSF. The clinical information, surgery-related results and radiographic outcome were collected and compared between the two groups. RESULTS: There was no significant difference between the two groups in total length of incisions, blood loss, post-operative hospitalization time, visual analog scale (VAS) score and Oswestry disability index (ODI) score. There was also no significant difference in the accuracy rate of pedicle screw placement between two groups; however, the facet joint violation (FJV) was significantly higher in the PPSF group. The atrophic area of multifidus muscle in the PPSF group is significantly larger than that in the MWPSF group and the operative time of MWPSF group was shorter than that in the PPSF group. Meanwhile, the PPSF group obtaining significantly more cumulative exposure to radiation (p < 0.001). The result of vertebral body angle (VBA), Cobb's angle and AVH rate in the MWPSF group were significantly better than those in the PPSF group at the last post-operative follow-up. CONCLUSIONS: Both minimally invasive treatment techniques (PPSF and MWPSF) are safe and effective in treatment of neurologically intact thoracolumbar fractures. Nevertheless, our results indicate that MWPSF may be a better choice for neurologically intact thoracolumbar fractures, since it protects multifidus muscle, and decreases facet joint violation, operation time, as well as radiation exposure. In addition, MWPSF was associated with better reduction of kyphosis.

Controllable Synthesis of Polyphenol Spheres via Amine-Catalyzed Polymerization-Induced Self-Assembly.

A facile and general strategy for preparing uniform and multifunctional polyphenol-based colloidal particles through amine-catalyzed polymerization-induced self-assembly is described. The size and interfacial adhesion of polyphenol spheres can be easily controlled over a wide range via adjusting the concentration of the cosolvent and monomer. Moreover, the polyphenol spheres showed excellent thermal and chemical stability and highly active properties and could efficiently deplete the reactive oxygen species (ROS), which are helpful for in vivo ROS regulation for inflammatory therapeutic. The accessible and versatile method provides a feasible way for the rational engineering of multifunctional polyphenol spheres, which have great potential in many fields.

Construction of a Risk Prediction Model for Hospital-Acquired Pulmonary Embolism in Hospitalized Patients.

The purpose of this study is to establish a novel pulmonary embolism (PE) risk prediction model based on machine learning (ML) methods and to evaluate the predictive performance of the model and the contribution of variables to the predictive performance. We conducted a retrospective study at the Shanghai Tenth People's Hospital and collected the clinical data of in-patients that received pulmonary computed tomography imaging between January 1, 2014 and December 31, 2018. We trained several ML models, including logistic regression (LR), support vector machine (SVM), random forest (RF), and gradient boosting decision tree (GBDT), compared the models with representative baseline algorithms, and investigated their predictability and feature interpretation. A total of 3619 patients were included in the study. We discovered that the GBDT model demonstrated the best prediction with an area under the curve value of 0.799, whereas those of the RF, LR, and SVM models were 0.791, 0.716, and 0.743, respectively. The sensibilities of the GBDT, LR, RF, and SVM models were 63.9%, 68.1%, 71.5%, and 75%, respectively; the specificities were 81.1%, 66.1, 72.7%, and 65.1%, respectively; and the accuracies were 77.8%, 66.5%, 72.5%, and 67%, respectively. We discovered that the maximum D-dimer level contributed the most to the outcome prediction, followed by the extreme growth rate of the plasma fibrinogen level, in-hospital duration, and extreme growth rate of the D-dimer level. The study demonstrates the superiority of the GBDT model in predicting the risk of PE in hospitalized patients. However, in order to be applied in clinical practice and provide support for clinical decision-making, the predictive performance of the model needs to be prospectively verified.

A novel hierarchical machine learning model for hospital-acquired venous thromboembolism risk assessment among multiple-departments.

Venous thromboembolism (VTE) is a common vascular disease and potentially fatal complication during hospitalization, and so the early identification of VTE risk is of significant importance. Compared with traditional scale assessments, machine learning methods provide new opportunities for precise early warning of VTE from clinical medical records. This research aimed to propose a two-stage hierarchical machine learning model for VTE risk prediction in patients from multiple departments. First, we built a machine learning prediction model that covered the entire hospital, based on all cohorts and common risk factors. Then, we took the prediction output of the first stage as an initial assessment score and then built specific models for each department. Over the duration of the study, a total of 9213 inpatients, including 1165 VTE-positive samples, were collected from four departments, which were split into developing and test datasets. The proposed model achieved an AUC of 0.879 in the department of oncology, which outperformed the first-stage model (0.730) and the department model (0.787). This was attributed to the fully usage of both the large sample size at the hospital level and variable abundance at the department level. Experimental results show that our model could effectively improve the prediction of hospital-acquired VTE risk before image diagnosis and provide decision support for further nursing and medical intervention.

Surface Grafting "Band-Aid" for "Everyone": Filter Paper-Assisted Surface-Initiated Polymerization in the Presence of Air.

We report herein a facile and generalized approach to the modification of solid surfaces with polymer brushes under ambient conditions: filter paper-assisted surface-initiated Cu0 -mediated controlled radical polymerization (PSI-CuCRP). The polymerization solution wetted filter paper is sandwiched between a copper plate and an initiator-modified substrate, which allows the creation of a surface-initiated polymerization (SIP) "band-aid" so that everyone can perform the surface grafting selectively with good control over the quality of the polymer brushes employing low concentration and microliter amounts of the monomer solution. The versatility of this method is demonstrated by grafting different homo-, block-, and multicomponent polymer brushes by using the same activation system and reaction conditions, the polymerization process can be precisely controlled to yield uniform polymers and show high chain-end functionality which is exemplified by in situ tetra-copolymerization. The combination of photolithography and paper cutting enables to prepare arbitrary three-dimensional patterned polymer brushes on the surface.