Modification of nanofibrous scaffolds to mimic extracellular matrix in physical and chemical structuring

Regulating the surface chemistry and topography of the scaffolds is an effective way to improve the scaffolds' biocompatibility. A nanofibrous scaffold with topographical and chemical biomimicry to ECM was developed in this study. In which, PCL nanofibrous scaffold was employed as a substrate which was shish-kebab structured first to provide the topographical similarity with ECM and then coated with polydopamine and arginylglycylaspartic acid (RGD) to endow the chemical biomimicry. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) results confirmed the successful grafting of RGD on the scaffolds. It was proved that the introduced shish-kebab structure and grafted RGD not only enhanced the surface roughness but also improved the surface wettability of the nanofibrous scaffolds. Human umbilical vein endothelial cells (HUVECs) exhibited a more flourishing living state onto the modified scaffolds. Moreover, the present modification method was further employed to graft other bioactive molecules (VEGF) onto the scaffold to further investigate its applicability. HEF1 fibroblast cells displayed great affinity on the modified scaffolds, indicating that the green modification approach was highly feasible to enhance the synthesized scaffolds' biocompatibility, which not only provides topographical similarity but also enhances the chemical biomimicry simultaneously.     

Enhanced Piezoelectric Performance of Electrospun PVDF-TrFE by Polydopamine-Assisted Attachment of ZnO Nanowires for Impact Force Sensing

In this work, piezoelectric PVDF-TrFE electrospun fibers (EFs) were fabricated using a high-throughput nozzle-free electrospinning process. Zinc oxide (ZnO) nanoparticles were robustly anchored to the PVDF-TrFE EFs, assisted by a self-polymerized polydopamine (PDA) layer, and subsequently grown into ZnO nanowires (NWs) using a low-temperature hydrothermal growth method. The EF mats were investigated for active impact force transduction and the piezoelectric voltage outputs of different combinations of PVDF-TrFE and ZnO nanomaterials were compared using two different impact force testing setups. The horizontal impact force test saw an increase in force sensitivity by a factor of 2.5 for the nanowires compared to the unmodified PVDF-TrFE EFs. Similarly, vertical drop impact testing demonstrated a 5.8-fold increase in sensitivity with a linear response (R² = 0.986) for a large range of impact forces up to 970 N. The EFs were also tested as a wearable impact force sensor to quantify soccer ball heading force, which was measured as 291.3 ± 51.0 N for a vertical ball speed of 7.8 ± 1.5 ms⁻¹¹ with an 8.2% average error compared to theoretical force values. It is believed the enhanced piezoelectric performance of these materials could provide a useful platform for wearable sensing and energy harvesting.     

聚多巴胺改性双醛壳聚糖的制备及其吸附性能

以壳聚糖(CS)为基材，采用高碘酸钠选择性氧化制备了双醛壳聚糖(DCS)，再通过接枝聚多巴胺(PDA)制得了环保型聚多巴胺/双醛壳聚糖(PDA/DCS)。采用SEM、FTIR、N₂吸附-脱附、XRD对两种改性壳聚糖进行了表征，并测试了其对胭脂红的吸附性能。结果表明，CS被高碘酸钠氧化后引入的活性基团醛基可与PDA产生共价结合，选择性氧化有效提高了DCS和PDA/DCS的吸附效果；与原CS相比，DCS结晶度明显下降，孔隙率和比表面积提高，PDA/DCS呈现较密集的多孔结构。DCS和PDA/DCS对胭脂红的吸附过程均遵循准二级动力学模型和Langmuir等温模型；但与DCS相比，PDA/DCS的吸附速率及吸附量明显提升，当染料初始质量浓度为700 mg/L时，PDA/DCS最大单分子层吸附量可达到1194.4 mg/g，且经过5次循环使用后，其吸附量仍达到616.90 mg/g。     

Three point bending and tensile properties of bio-additive polydopamine-coated 3D printing-based distal ulna small locking bone plates: Future need of orthopedic implants

Polylactic acid (PLA)-based implants fabricated by 3D Printing process are biocompatible, porous in nature and light in weight. These biomimetic implants can be used as an alternative to metallic implants. However, such PLA-based implants lack mechanical strength, limiting their application in biomedical field. In the present study, direct immersion coating technique has been used for application of polydopamine coating followed by studying the effect of input process parameters such as infill density, immersion time, speed of incubator shaker and concentration of coating solution using response surface methodology (RSM)-based approach. Analysis of variance (ANOVA) has been applied for prediction of statistical models with respect to ultimate tensile and flexural strengths. The effect of individual process parameters has been discussed using main effect plots and the interactions occurring between significant parameters has been discussed using response surface and contour plots. From the findings, it was evident that infill density was highly significant parameter followed by immersion time, speed of incubator shaker and concentration of coating solution. Also, the mechanical properties improved with increase in infill density and immersion time. However, they initially increased and then decreased with increase in speed of incubator shaker and concentration of coating solution.     

The polydopamine-assisted heparin anchor enhances the hydrophilicity,hemocompatibility, and biocompatibility of polyurethane

Surface heparinization is an effective solution to resolve low endothelialization, poor anticoagulation, and hemocompatibility of polyurethane (PU) used as materials of small-diameter vascular grafts. Here, the effects of polydopamine (PDA) and poly (acrylic acid) (PAA) as crosslinking agents on the surface heparinization were explored. The PU membranes grafted with heparin (Hep) via dopamine (PU/PDA-Hep) showed better hydrophilicity and stability, compared to heparinized PU membranes via acrylic acid (PU/PAA-Hep). The results of X-ray photoelectron spectroscopy demonstrated that heparin was successfully grafted onto the PU surface and the grafting efficiency was high when PDA as a cross-linking agent. The grafted heparin aggregated and formed nanoparticles, and increased the surface roughness of PU membranes. The heparinized membranes demonstrated good anti-adhesion of bovine serum albumin and fibrin protein. In addition, no activated platelets or educts on heparinized PU were found by platelet adhesion tests, implying that heparin-immobilized surfaces had good hemocompatibility. Moreover, the in vitro cytocompatibility assessment showed that the PU/PDA-Hep significantly improved the proliferation of L929 cells and was superior to PU/AA-Hep. These results demonstrated that PDA-assisted surface heparinization was an effective method to improve the anticoagulant and biocompatibility of PU small-diameter vascular materials and could be extended to other implantable materials.     

Effect of infill pattern on the mechanical properties of polydopamine-coated polylactic acid orthopedic bone plates developed by fused filament fabrication

Distal fractures are the most commonly experienced type of fractures that require fixation of bone plates for healing of fractured bones. Poly Lactic Acid (PLA)-based bone plates are porous and light in weight. However, they lack mechanical properties that limit their application in biomedical field. Polydopamine coating has been witnessed to undergo covalent interactions, enhancing the mechanical properties of the substrate. The present study is based on the fabrication of PLA-based bone plates using Fused Filament Fabrication with varying infill patterns. The infill patterns in the study include octet, cubic, grid, concentric, lines, and gyroid. Thereafter, polydopamine coating was deposited on these bone plates using direct immersion coating method. In the study, the effect of infill pattern on coating deposition and modification of mechanical properties has been studied. The microscopic images of fractured bone plates were captured. It was concluded that polydopamine coating was successful in improving mechanical properties for all infill patterns. The findings suggested that a concentric pattern should be used for applications that require both high mechanical strength and maximum elongation at break because elongation at break is higher for concentric patterns than gyroid patterns. Also, for applications requiring only high mechanical strength, a gyroid pattern should be used.     

Precision Delivery of Dual Immune Inhibitors Loaded Nanomodulator to Reverse Immune Suppression for Combinational Photothermal-Immunotherapy (Small 21/2023)

Although photothermal therapy (PTT) can noninvasively kill tumor cells and exert synergistic immunological effects, the immune responses are usually harmed due to the lack of cytotoxic T cells (CTLs) pre-infiltration and co-existing of intricate immunosuppressive tumor microenvironment (TME), including the programmed cell death ligand 1 (PD-L1)/cluster of differentiation 47 (CD47)/regulatory T cells (Tregs)/M2-macrophages overexpression. Indoleamine 2, 3-dioxygenase inhibitor (NLG919) or bromodomain extra-terminal inhibitor (OTX015) holds great promise to reprogram suppressive TME through different pathways, but their collaborative application remains a formidable challenge because of the poor water solubility and low tumor targeting. To address this challenge, a desirable nanomodulator based on dual immune inhibitors loaded mesoporous polydopamine nanoparticles is designed. This nanomodulator exhibits excellent biocompatibility and water solubility, PTT, and bimodal magnetic resonance/photoacoustic imaging abilities. Owing to enhanced permeability and retention effect and tumor acidic pH-responsiveness, both inhibitors are precisely delivered and locally released at tumor sites. Such a nanomodulator significantly reverses the immune suppression of PD-L1/CD47/Tregs, promotes the activation of CTLs, regulates M2-macrophages polarization, and further boosts combined therapeutic efficacy, inducing a strong immunological memory. Taken together, the nanomodulator provides a practical approach for combinational photothermal-immunotherapy, which may be further broadened to other “immune cold” tumors.     

PDA/SiO2改性聚氨酯制备含结构色复合材料

采用改良St?ber法制得187、245、274 nm 3种粒径的SiO2微球，使用聚多巴胺（PDA）对SiO2微球进行包覆，制备了蓝色、绿色、红色3种不同颜色的非晶光子晶体PDA/SiO2（APCs）；将非晶光子晶体PDA/SiO2引入聚氨酯（PU）制得复合材料PDA/SiO2/PU 。利用FT-IR、CA、SEM、TEM、UV-Vis、DLS及万能试验机对PDA/SiO2及复合材料PDA/SiO2/PU的结构与性能进行表征分析。结果表明：APCs的颜色取决于SiO2微球的粒径；通过调节PDA的包覆量可调整APCs的色彩饱和度；APCs引入PU后可得到呈暗红结构色聚氨酯，其最大拉伸强度可达40.28 MPa，水接触角达113°，使得聚氨酯具有结构生色性和优异的机械性能与疏水性。     

具有PDA-UiO-66中间层耐溶剂复合纳滤膜的制备及性能

将多巴胺和Ui O-66纳米颗粒共沉积在经1,6-己二胺交联的聚醚酰亚胺（PEI）基膜上构建了纳米复合中间层（PDA-UiO-66），并在中间层上进行界面聚合反应制备了耐溶剂复合纳滤膜（TFN-U）。通过FTIR、XRD、SEM、AFM、水接触角测量仪对膜结构进行了表征和测试，探究了Ui O-66质量浓度对TFN-U膜耐溶剂性、耐污染性以及运行稳定性的影响。结果表明，PDA-Ui O-66纳米复合中间层的引入能提高TFN-U膜的渗透通量，当Ui O-66纳米颗粒质量浓度为0.2 g/L时，TFN-U2膜水通量为63.83 L/(m2·h)，甲醇通量为28.50L/(m2·h)，对刚果红水溶液和刚果红甲醇溶液的截留率为98.2%和93.2%，经无水乙醇、丙酮、乙酸乙酯、正己烷及N,N-二甲基甲酰胺（DMF）浸泡48h后，其对刚果红的截留率均>94%，通量恢复率达到78.1%，在连续24 h过滤刚果红甲醇溶液后，该膜的甲醇通量为14.13L/(m2·h)，截留率为98.3%，表明TFN-U2膜具有良好的耐溶剂性、耐污染性以及一定的运行稳定性。