Exploration of Genome-Wide Recombination Rate Variation Patterns at Different Scales in Pigs.

Meiotic recombination is a prevalent process in eukaryotic sexual reproduction organisms that plays key roles in genetic diversity, breed selection, and species evolution. However, the recombination events differ across breeds and even within breeds. In this study, we initially computed large-scale population recombination rates of both sexes using approximately 52 K SNP genotypes in a total of 3279 pigs from four different Chinese and Western breeds. We then constructed a high-resolution historical recombination map using approximately 16 million SNPs from a sample of unrelated individuals. Comparative analysis of porcine recombination events from different breeds and at different resolutions revealed the following observations: Firstly, the 1Mb-scale pig recombination maps of the same sex are moderately conserved among different breeds, with the similarity of recombination events between Western pigs and Chinese indigenous pigs being lower than within their respective groups. Secondly, we identified 3861 recombination hotspots in the genome and observed medium- to high-level correlation between historical recombination rates (0.542~0.683) and estimates of meiotic recombination rates. Third, we observed that recombination hotspots are significantly far from the transcription start sites of pig genes, and the silico-predicted PRDM9 zinc finger domain DNA recognition motif is significantly enriched in the regions of recombination hotspots compared to recombination coldspots, highlighting the potential role of PRDM9 in regulating recombination hotspots in pigs. Our study analyzed the variation patterns of the pig recombination map at broad and fine scales, providing a valuable reference for genomic selection breeding and laying a crucial foundation for further understanding the molecular mechanisms of pig genome recombination.

Biomimetic design of micro- and nano-wrinkle wood surface via coating reinforced with hyperbranched polymer grafted cellulose nanofibers for skin-tactile performance.

Inspired from human skin, micro- and nano-wrinkled wood surface with skin-tactile performance was designed and developed using a waterborne UV-curable polyurethane acrylate coating and cellulose nofibers (CNF). To further improve the properties, the CNF was diacetylated to D-CNF and further grafted with a hyperbranched polymer containing rich end amino groups (HB-CNF). The surface structure and chemical reactions were characterized, and the skin-tactile performance of the coating was comprehensively investigated. The HB-CNF exhibited excellent dispersion in the coating, and extensive reactions occurred between the two through the -NH2 and terminal -NCO groups, resulting in much improved mechanical properties and durability. Micro-wrinkles with a width of approximately 12-15 µm and a height of 8-14 µm were created, and nano-protrusions of wrinkles ranging from to 50-100 nm were obtained. The coated surface was hydrophobic and exhibited high resilience after compression, with a gloss of 3.3 GU at an incident angle of 60° and a static friction coefficient of 0.26, both of which were similar to those of human skin. The results presented an effective strategy for high-performance wood products with a good feeling, which is helpful to improve the market competitiveness and meet the people's pursuit of a better life.

A novel self-wrinkled polyurethane-acrylate wood coating with self-matting, anti-fingerprint performance and skin-tactile feeling via excimer lamp/UV curing.

Wrinkled surfaces exist widely in nature and organic living world, such as plants, insects, and skin. The optical, wettability and mechanical properties of materials can be enhanced by artificially preparing regular microstructure on the surface of materials. In this study, a novel self-wrinkled polyurethane-acrylate (PUA) wood coating with self-matting, anti-fingerprint performance and skin-tactile feeling curing by excimer lamp (EX) and ultraviolet (UV) was prepared. The wrinkles were formed on the surface of PUA coating at microscopic level after excimer and UV mercury lamp irradiation. The width and height of the wrinkles on the coating surface can be controlled to adjust the coating performance by changing the curing energy. When the PUA coating samples were cured by excimer lamp and UV mercury lamp with curing energy of 25-40 mJ cm-2 and 250-350 mJ cm-2, the excellent coating performances were observed. The gloss value of self-wrinkled PUA coating at 20° and 60° were less than 3 GU, while at 85° was 6.5 GU, which satisfied the demanding of matting coating. Besides, the fingerprints on the coating samples could disappear in 30 s and could still have anti-fingerprint performance after 150 times of anti-fingerprint tests. Furthermore, the pencil hardness, abrasion quantity and adhesion of self-wrinkled PUA coating were 3H, 0.045 g and 0 grade respectively. Finally, the self-wrinkled PUA coating has excellent skin-tactile feeling for touching. The coating can be applied to wood substrates, and has potential application in the field of wood-based panels, furniture and leather.

Construction of a transposase accessible chromatin landscape reveals chromatin state of repeat elements and potential causal variant for complex traits in pigs.

BACKGROUND: A comprehensive landscape of chromatin states for multiple mammalian tissues is essential for elucidating the molecular mechanism underlying regulatory variants on complex traits. However, the genome-wide chromatin accessibility has been only reported in limited tissue types in pigs. RESULTS: Here we report a genome-wide landscape of chromatin accessibility of 20 tissues in two female pigs at ages of 6 months using ATAC-seq, and identified 557,273 merged peaks, which greatly expanded the pig regulatory element repository. We revealed tissue-specific regulatory elements which were associated with tissue-relevant biological functions. We identified both positive and negative significant correlations between the regulatory elements and gene transcripts, which showed distinct distributions in terms of their strength and distances from corresponding genes. We investigated the presence of transposable elements (TEs) in open chromatin regions across all tissues, these included identifications of porcine endogenous retroviruses (PERVs) exhibiting high accessibility in liver and homology of porcine specific virus sequences to universally accessible transposable elements. Furthermore, we prioritized a potential causal variant for polyunsaturated fatty acid in the muscle. CONCLUSIONS: Our data provides a novel multi-tissues accessible chromatin landscape that serve as an important resource for interpreting regulatory sequences in tissue-specific and conserved biological functions, as well as regulatory variants of loci associated with complex traits in pigs.

Electroacupuncture Ameliorates Depressive-Like Behaviors in Poststroke Rats via Activating the tPA/BDNF/TrkB Pathway.

BACKGROUND: Electroacupuncture (EA) is a form of physical therapy that has been widely used in clinical practice in China. Post-stroke depression (PSD) is the most common neuropsychiatric complication after stroke. EA has been shown to have beneficial effects on PSD patients. However, the potential mechanism underlying the protective effects of EA on PSD remains unclear. Here, we investigated whether tissue plasminogen activator (tPA)/brain-derived neurotrophic factor (BDNF)/tyrosine kinase receptor B (TrkB) signaling pathway participates in the therapeutic effects of EA in a rat PSD model. METHODS: Experimental PSD was induced by combining middle cerebral artery occlusion (MCAO) with chronic unpredictable mild stimulation (CUMS) in adult male rats. Bodyweight gain, neurological score, sucrose preference, and open field test were determined at 0, 7, 14, and 35 days after completing MCAO. The protein expressions of tPA, precursor BDNF (proBDNF), mature BDNF (mBDNF), and TrkB were measured by immunofluorescence and Western blot analysis. The tPA inhibitor plasminogen inhibitor-1 (PAI-1) was used to explore whether tPA plays a crucial role in the protective effects of EA on PSD. RESULTS: Compared with the sham rats, the PSD rats showed decreased bodyweight, deteriorated neurological score, and significant depressive-like behaviors. EA remarkably reversed bodyweight loss, neurological deficit, and depressive-like behaviors in PSD rats. Immunofluorescence staining and Western blot analysis showed that PSD-induced decreased expression of tPA, mBDNF, and TrkB were prevented by EA. Furthermore, we found that the effects of EA against PSD-induced depressive-like behaviors were abolished by PAI-1, the specific inhibitor of tPA. CONCLUSION: Our results suggest that the improvement in depressive-like behaviors induced by EA is likely achieved via activation of the tPA/BDNF/TrkB pathway.

Single-Cell Sequencing Confirms Transcripts and VHDJH Rearrangements of Immunoglobulin Genes in Human Podocytes.

Most glomerular diseases are associated with inflammation caused by deposited pathogenic immunoglobulins (Igs), which are believed to be produced by B cells. However, our previous study indicated that the human podocyte cell line can produce IgG. In this study, we aimed to confirm the transcripts and characterize the repertoires of Igs in primary podocytes at single cell level. First, single-cell RNA sequencing of cell suspensions from "normal" kidney cortexes by a 10xGenomics Chromium system detected Ig transcripts in 7/360 podocytes and Ig gene segments in 106/360 podocytes. Then, we combined nested PCR with Sanger sequencing to detect the transcripts and characterize the repertoires of Igs in 48 single podocytes and found that five classes of Ig heavy chains were amplified in podocytes. Four-hundred and twenty-nine VHDJH rearrangement sequences were analyzed; podocyte-derived Igs exhibited classic VHDJH rearrangements with nucleotide additions and somatic hypermutations, biased VH1 usage and restricted diversity. Moreover, compared with the podocytes from healthy control that usually expressed one class of Ig and one VHDJH pattern, podocytes from patients expressed more classes of Ig, VHDJH patterns and somatic hypermutations. These findings suggested that podocytes can express Igs in normal condition and increase diversity in pathological situations.

Subcutaneous and intramuscular fat transcriptomes show large differences in network organization and associations with adipose traits in pigs.

Subcutaneous fat (SCF) and intramuscular fat (IMF) deposition is relevant to health in humans, as well as meat production and quality in pigs. In this study, we generated RNA sequence data for 122 SCF, 120 IMF, and 87 longissimus dorsi muscle (LDM) samples using 155 F6 pigs from a specially designed heterogeneous population generated by intercrossing four highly selected European commercial breeds and four indigenous Chinese pig breeds. The phenotypes including waist back fat thickness and intramuscular fat content were also measured in the 155 F6 pigs. We found that the genes in SCF and IMF differed largely in both expression levels and network connectivity, and highlighted network modules that exhibited strongest gain of connectivity in SCF and IMF, containing genes that were associated with the immune process and DNA double-strand repair, respectively. We identified 215 SCF genes related to kinase inhibitor activity, mitochondrial fission, and angiogenesis, and 90 IMF genes related to lipolysis and fat cell differentiation, displayed a tissue-specific association with back fat thickness and IMF content, respectively. We found that cis-expression QTL for trait-associated genes in the two adipose tissues tended to have tissue-dependent predictability for the two adipose traits. Alternative splicing of genes was also found to be associated with SCF or IMF deposition, but the association was much less extensive than that based on expression levels. This study provides a better understanding of SCF and IMF gene transcription and network organization and identified critical genes and network modules that displayed tissue-specific associations with subcutaneous and intramuscular fat deposition. These features are helpful for designing breeding programs to genetically improve the two adipose traits in a balanced way.

Mechanically Robust and Reprocessable Acrylate Vitrimers with Hydrogen-Bond-Integrated Networks for Photo-3D Printing.

Reprocessable acrylate vitrimer needs to enhance its strength to expand the application in photo-three-dimensional (photo-3D) printing. However, the methods for improving mechanical properties by the addition of nanofillers or a multifunctional resin into acrylate vitrimers are inappropriate for photo-3D printing due to the low curing speed of photopolymerization induced by weakening light transmittance or reduction of dimensional accuracy caused by large shrinkage. At present, we demonstrate a new strategy for developing a kind of mechanically robust and reprocessable 3D printing thermosets by combining hydrogen bonds and exchangeable ß-hydroxyl esters into acrylate vitrimers. To realize this purpose, diacrylate prepolymer containing ß-hydroxyl esters was first synthesized from glycidyl methacrylate and suberic acid. Then, the resin formulations for 3D printing comprising the synthesized diacrylate prepolymer together with acrylamide generate exchanged ß-hydroxyl ester and pendent amide in cross-linked networks. Here, hydrogen bonds resulting from the amide group as sacrificial bonds dissipate vast mechanical energy under an external load. With the inclusion of 20 wt % acrylamide, the average tensile strength and Young's modulus are up to 40.1 and 871 MPa, which increased by about 4.4 and 3.85 times, respectively. The network rearrangement of cross-linked vitrimers can be achieved through the dynamic ester exchange reactions with gradual disappearance of hydrogen bonds at elevated temperatures, imparting reprocessability into the printed structures. Various photo-3D printing or UV irradiation shapes were successfully produced, and these dissolved in ethylene glycol could be remolded again.

Single-cell RNA sequencing confirms IgG transcription and limited diversity of VHDJH rearrangements in proximal tubular epithelial cells.

Increasing evidence has confirmed that immunoglobulins (Igs) can be expressed in non-B cells. Our previous work demonstrated that mesangial cells and podocytes express IgA and IgG, respectively. The aim of this work was to reveal whether proximal tubular epithelial cells (PTECs) express Igs. High-throughput single-cell RNA sequencing (scRNA-seq) detected Igs in a small number of PTECs, and then we combined nested PCR with Sanger sequencing to detect the transcripts and characterize the repertoires of Igs in PTECs. We sorted PTECs from the normal renal cortex of two patients with renal cancer by FACS and further confirmed their identify by LRP2 gene expression. Only the transcripts of the IgG heavy chain were successfully amplified in 91/111 single PTECs. We cloned and sequenced 469 VHDJH transcripts from 91 single PTECs and found that PTEC-derived IgG exhibited classic VHDJH rearrangements with nucleotide additions at the junctions and somatic hypermutations. Compared with B cell-derived IgG, PTEC-derived IgG displayed less diversity of VHDJH rearrangements, predominant VH1-24/DH2-15/JH4 sequences, biased VH1 usage, centralized VH gene segment location at the 3' end of the genome and non-Gaussian distribution of the CDR3 length. These results demonstrate that PTECs can express a distinct IgG repertoire that may have implications for their role in the renal tubular epithelial-mesenchymal transition.

Application of a Strontium-Loaded, Phase-Transited Lysozyme Coating to a Titanium Surface to Enhance Osteogenesis and Osteoimmunomodulation.

BACKGROUND To fabricate strontium (Sr)-incorporated titanium (Ti) surfaces by a novel 1-step phase-transited lysozyme (PTL) treatment, and investigate the effects of the prepared samples on osteogenesis and osteoimmunoregulation. MATERIAL AND METHODS Five groups of titanium specimens were prepared, including Ti, PTL, PTL@10Sr (PTL coating with 10 mg/mL Sr), PTL@20Sr PTL coating with 20 mg/mL Sr), and PTL@50Sr (PTL coating with 50 mg/mL Sr) groups. Behaviors of bone marrow mesenchymal stem cells (BMSCs) such as initial attachment, spread, proliferation, and migration, on different surfaces were examined by immunofluorescence, MTS assay, and Transwell system. Then the osteogenic differentiation of BMSCs was detected. When an immune response was factored in, the polarization of macrophages induced by the prepared surfaces was detected by real-time PCR, and the response of BMSCs to macrophage-conditioned medium was assessed in terms of cell migration and osteogenic differentiation. Finally, an in vivo study was performed, using the rat femora implant model, to evaluate the potential for osteogenic induction and osteoimmunoregulation of materials. RESULTS Our in vitro experiments indicated that PTL coating could improve cell spread and adhesion, and the stable Sr release of PTL@Sr layers could promote cell migration and osteogenesis. Moreover, PTL@Sr surface could regulate the immune response of macrophages resulting in enhanced BMSCs recruitment and osteogenic differentiation. The in vivo evaluation showed less inflammatory infiltration and improved bone formation in the PTL@20Sr group. CONCLUSIONS The Sr-loaded PTL layers have greater potential for the induction of osteogenic differentiation of BMSCs, meanwhile Sr-loaded PTL layers could adjust the immune response and thus promote osteogenesis both in vitro and in vivo.

Differential Expression Profiles and Functional Prediction of tRNA-Derived Small RNAs in Rats After Traumatic Spinal Cord Injury.

Spinal cord injury (SCI) is mostly caused by trauma. As the primary mechanical injury is unavoidable, a focus on the underlying molecular mechanisms of the SCI-induced secondary injury is necessary to develop promising treatments for patients with SCI. Transfer RNA-derived small RNA (tsRNA) is a novel class of short, non-coding RNA, possessing potential regulatory functions in various diseases. However, the functional roles of tsRNAs in traumatic SCI have not been determined yet. We used a combination of sequencing, quantitative reverse transcription-polymerase chain reaction (qRT-PCR), bioinformatics, and luciferase reporter assay to screen the expression profiles and identify the functional roles of tsRNAs after SCI. As a result, 297 differentially expressed tsRNAs were identified in rats' spinal cord 1 day after contusion. Of those, 155 tsRNAs were significantly differentially expressed: 91 were significantly up-regulated, whereas 64 were significantly down-regulated after SCI (fold change > 1.5; P < 0.05). Bioinformatics analyses revealed candidate tsRNAs (tiRNA-Gly-GCC-001, tRF-Gly-GCC-012, tRF-Gly-GCC-013, and tRF-Gly-GCC-016) that might play regulatory roles through the mitogen-activated protein kinase (MAPK) and neurotrophin signaling pathways by targeting brain-derived neurotrophic factor (BDNF). We validated the candidate tsRNAs and found opposite trends in the expression levels of the tsRNAs and BDNF after SCI. Finally, tiRNA-Gly-GCC-001 was identified to target BDNF using the luciferase reporter assay. In summary, we found an altered tsRNA expression pattern and predicted tiRNA-Gly-GCC-001 might be involved in the MAPK and neurotrophin pathways by targeting the BDNF, thus regulating the post-SCI pathophysiologic processes. This study provides novel insights for future investigations to explore the mechanisms and therapeutic targets for SCI.

Reduced Expression of Deubiquitinase USP33 Is Associated with Tumor Progression and Poor Prognosis of Gastric Adenocarcinoma.

BACKGROUND Ubiquitin-specific peptidase 33 (USP33) is a deubiquitinase that balances the ubiquitin status of proteins. It has been reported to act as a tumor suppressor in colorectal cancer and lung cancer. However, the expression pattern and clinical significance of USP33 have not been investigated in gastric adenocarcinoma (GAC). MATERIAL AND METHODS We explored the USP33 protein and RNA levels by immunohistochemistry (IHC), Western blot analysis, and qRT-PCR. The Pearson chi-square test was performed to evaluate the statistical associations between USP33 level and patient characteristics. Additionally, the relationship between USP33 expression and patient survival was investigated. Cellular studies, including proliferation assay, migration assay, and invasion assay, were conducted to demonstrate the underlying mechanisms of USP33 in GAC progression. RESULTS This study included 121 patients with GAC. USP33 showed a decreased expression in GAC tissues compared to adjacent normal gastric tissues. Low expression of USP33 was correlated with invasion depth and advanced TNM stage. According to survival analysis, upper location of tumor (P=0.003), invasion depth (P=0.048), advanced TNM stage (P=0.001), and low USP33 level (P=0.001) were all associated with poor overall survival of GAC patients. Cox analysis confirmed the independent role of USP33 in predicting patient survival. Cell experiments showed that USP33 overexpression significantly inhibited the proliferation, migration, and invasion of GAC cells. CONCLUSIONS USP33 was downregulated in GAC, and was an independent prognostic factor. In vitro results demonstrated the role of USP33 in suppressing tumor progression, suggesting that the developing an agonist of USP33 may be a novel direction for chemotherapy development.

The effectiveness of therapeutic strategies for patients with radiculopathy: A network meta-analysis.

Objectives The aim of this network meta-analysis is to assess the effectiveness of therapeutic strategies for patients with radiculopathy, including physical, medical, surgical, and other therapies. Methods We electronically searched electronic databases including PubMed and Embase for randomized controlled trials. The response rate and visual analog scale of pain change were considered as primary outcomes. The outcomes were measured by odds ratio (OR) value and corresponding 95% credible intervals (CrIs) or standardized mean difference (MD) with 95% CrIs. Besides, surface under cumulative ranking curve (SUCRA) were performed to rank efficacy and safety of treatments on each end points. Results A total of 16 eligible studies with 1071 subjects were included in this analysis. Our results showed that corticosteroid was significantly more effective than control regarding the response rate (OR = 3.86, 95% CrI: 1.16, 12.55). Surgery had a better performance in pain change compared with control (MD = -1.92, 95% CrI: -3.58, -0.15). According to the SUCRA results, corticosteroid, collar, and physiotherapy ranked the highest concerning response rate (SUCRA = 0.656, 0.652, and 0.610, respectively). Surgery, traction, and corticosteroid were superior to others in pain change (SUCRA = 0.866, 0.748, and 0.589, respectively). Conclusion According to the network meta-analysis result, we recommended surgery as the optimal treatment for radiculopathy patients; traction and corticosteroids were also recommended for their beneficial interventions.

Asymmetric Collagen/chitosan Membrane Containing Minocycline-loaded Chitosan Nanoparticles for Guided Bone Regeneration.

Infections caused by pathogens colonization at wound sites in the process of bone healing are considered as one of the major reasons for the failure of guided bone regeneration (GBR). The objective of this study was to prepare a novel asymmetric collagen/chitosan GBR membrane containing minocycline-loaded chitosan nanoparticles. The morphologies of the membranes and nanoparticles were observed by SEM and TEM, respectively. The characterization and biocompatibility of the membranes was evaluated. The effect of the membrane on bone regeneration was assessed using the critical-size at cranial defect model. TEM images showed the spherical morphology of the nanoparticles. The results of SEM indicated that the asymmetric membrane contained a dense collagen layer and a loose chitosan layer. An in vitro experiment showed that the membrane can inhibit bacterial growth and promote osteoblasts and fibroblasts growth. The membrane showed the ability to promote angiogenesis and enhance bone regeneration in vivo. An asymmetric collagen/chitosan GBR membrane can be fabricated by loading minocycline encapsulated chitosan nanoparticles, and shows satisfactory biocompatibility and barrier function, which enhances bone regeneration. Therefore, this antibacterial GBR membrane is a promising therapeutic approach to prevent infection and guide bone regeneration.

Microparticles and blood cells induce procoagulant activity via phosphatidylserine exposure in NSTEMI patients following stent implantation.

BACKGROUND: Relatively little is known about the role of phosphatidylserine (PS) in procoagulant activity (PCA) in patients with non-ST-elevated myocardial infarction (NSTEMI) after stent implantation. This study was designed to evaluate whether exposed PS on microparticles (MPs) and blood cells were involved in the hypercoagulable state in NSTEMI patients with stent implantation. METHODS: NSTEMI patients (n=90) and healthy controls (n=20) were included in our study. PS exposure on MPs and blood cells was analyzed with flow cytometer and confocal microscope. PCA was evaluated by clotting time, purified coagulation complex assays and fibrin production assays. RESULTS: Baseline levels of MPs and PS+ blood cells were significantly higher (P<0.001) in the patients than in controls. After stent implantation, a remarkable increase was observed in both MPs and PS+ blood cells. Specifically, PS+ MPs, PS+ platelets and erythrocytes peaked at 18h following stent implantation, while PS+ leukocytes peaked on day 2. In addition, circulating MPs (mostly derived from platelets, leukocytes, erythrocytes and endothelial cells) cooperating with PS+ blood cells, contributed to markedly shortened coagulation time and markedly increased FXa/thrombin/fibrin (all P<0.01) generation in patient group. Moreover, blockade of exposed PS on MPs and cells with lactadherin inhibited PCA by approximately 70%. CONCLUSIONS: Our results suggest that PS+ MPs and blood cells play a procoagulant role in NSTEMI patients following stent implantation. Blockade of PS could become a novel therapeutic modality for the prevention of thrombosis in these patients.

Monte Carlo Study of Degenerate Behavior of AB Diblock Copolymer/Nanoparticle under Cylindrical Confinement.

Degenerate behavior (i.e., forming different self-assembled structures for a given block copolymer (BCP) under the same confinement) commonly exists in various confined systems. Understanding degenerate behavior is crucial for precise control over the structures formed by self-assembly systems under confinement. In this study, the degenerate behavior of a self-assembled AB diblock copolymer/nanoparticle (NP) mixture in a cylindrical pore is studied using Monte Carlo simulation. We find that the degenerate behavior of such a mixture depends on the introduction of the NP. Under different pore sizes, four typical degenerate structures [i.e., single helices (S-helices), double helices (D-helices), parallel cylinders, and stacked toroids] can be obtained if the NP content is zero. However, when the NP content in the mixture is increased, it is found that the number of degenerate structures decreases, that is, only blocky structures can be obtained in the case of high NP content. Moreover, the probability of forming S-helices decreases, whereas the probability of forming D-helices increases with increase in the NP content. Analysis of the interactive enthalpy densities and the chain conformation of the systems indicates that entropy plays an important role in the degenerate structure formation. This study provides some new insights into the degenerate behavior of a BCP/NP mixture under confinement, which can offer a theoretical reference for further experiments.

Modification of Titanium Substrates with Chimeric Peptides Comprising Antimicrobial and Titanium-Binding Motifs Connected by Linkers To Inhibit Biofilm Formation.

Bacterial adhesion and biofilm formation are the primary causes of implant-associated infection, which is difficult to eliminate and may induce failure in dental implants. Chimeric peptides with both binding and antimicrobial motifs may provide a promising alternative to inhibit biofilm formation on titanium surfaces. In this study, chimeric peptides were designed by connecting an antimicrobial motif (JH8194: KRLFRRWQWRMKKY) with a binding motif (minTBP-1: RKLPDA) directly or via flexible/rigid linkers to modify Ti surfaces. We evaluated the binding behavior of peptides using quartz crystal microbalance (QCM) and atomic force microscopy (AFM) techniques and investigated the effect of the modification of titanium surfaces with these peptides on the bioactivity of Streptococcus gordonii (S. gordonii) and Streptococcus sanguis (S. sanguis). Compared with the flexible linker (GGGGS), the rigid linker (PAPAP) significantly increased the adsorption of the chimeric peptide on titanium surfaces (p < 0.05). Concentration-dependent adsorption is consistent with a single Langmuir model, whereas time-dependent adsorption is in line with a two-domain Langmuir model. Additionally, the chimeric peptide with the rigid linker exhibited more effective antimicrobial ability than the peptide with the flexible linker. This finding was ascribed to the ability of the rigid linker to separate functional domains and reduce their interference to the maximum extent. Consequently, the performance of chimeric peptides with specific titanium-binding motifs and antimicrobial motifs against bacteria can be optimized by the proper selection of linkers. This rational design of chimeric peptides provides a promising alternative to inhibit the formation of biofilms on titanium surfaces with the potential to prevent peri-implantitis and peri-implant mucositis.

Recording the dynamic endocytosis of single gold nanoparticles by AFM-based force tracing.

We utilized force tracing to directly record the endocytosis of single gold nanoparticles (Au NPs) with different sizes, revealing the size-dependent endocytosis dynamics and the crucial role of membrane cholesterol. The force, duration and velocity of Au NP invagination are accurately determined at the single-particle and microsecond level unprecedentedly.

Guided bone regeneration with tripolyphosphate cross-linked asymmetric chitosan membrane.

OBJECTIVES: The objective of this study was to prepare a novel asymmetric chitosan guided bone regeneration (GBR) membrane, which is composed of a dense layer isolating the bone defect from the invasion of surrounding connective fibrous tissue and a loose layer which can improve cell adhesion and stabilize blood clots, thus guided bone regeneration. METHODS: The chitosan membrane was fabricated through liquid nitrogen quencher combined with lyophilization and cross-linked by sodium tripolyphosphate (TPP). The physical properties of asymmetric chitosan membrane were measured by scanning electron microscope (SEM), Fourier-transform infrared (FTIR), x-ray diffraction (XRD) and tensile test machine. MTT assay and Live/Dead cell staining for MC3T3-E1 osteoblasts cultured on the membrane were used to characterize the biocompatibility of the membrane. In animal experiments, full-thickness and critical sized skull defects were made to evaluate the effect of the membrane on bone regeneration. RESULTS: The results of this study indicate that the asymmetric chitosan membrane can be built and cross-linked by TPP to enhance the tensile strength of the membrane. In vitro experiment showed that no significant numbers of dead cells were detected on the chitosan membrane, indicating that the membrane had good biocompatibility. In animal experiments, the chitosan membrane had faster new bone formation, showing the capability to enhance bone regeneration. CONCLUSIONS: The chitosan membrane prepared in this study has an asymmetric structure; its tensile strength, biodegradation and biocompatibility fulfil the requirements of guided bone regeneration. Therefore, the asymmetric chitosan membrane is a promising GBR membrane for bone regeneration. CLINICAL SIGNIFICANCE: Guided bone regeneration (GBR) is an effective method for healing bone defects caused by periodontitis and implantitis, in which GBR membrane is a key biomaterial.