3D printable elastomers with exceptional strength and toughness.

Three-dimensional (3D) printing has emerged as an attractive manufacturing technique because of its exceptional freedom in accessing geometrically complex customizable products. Its potential for mass manufacturing, however, is hampered by its low manufacturing efficiency (print speed) and insufficient product quality (mechanical properties). Recent progresses in ultra-fast 3D printing of photo-polymers1-5 have alleviated the issue of manufacturing efficiency, but the mechanical performance of typical printed polymers still falls far behind what is achievable with conventional processing techniques. This is because of the printing requirements that restrict the molecular design towards achieving high mechanical performance. Here we report a 3D photo-printable resin chemistry that yields an elastomer with tensile strength of 94.6 MPa and toughness of 310.4 MJ m-3, both of which far exceed that of any 3D printed elastomer6-10. Mechanistically, this is achieved by the dynamic covalent bonds in the printed polymer that allow network topological reconfiguration. This facilitates the formation of hierarchical hydrogen bonds (in particular, amide hydrogen bonds), micro-phase separation and interpenetration architecture, which contribute synergistically to superior mechanical performance. Our work suggests a brighter future for mass manufacturing using 3D printing.

Anlotinib alone or in combination with bevacizumab in the treatment of recurrent high-grade glioma: a prospective single-arm, open-label phase II trial.

BACKGROUND: Anlotinib is a multi-target tyrosine kinase inhibitor (TKI) targeting the vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR), fibroblast growth factor receptor (FGFR), and c-Kit. This phase II study aimed to assess the efficacy and safety of anlotinib, either alone or in combination with bevacizumab (Bev) for recurrent high-grade glioma (rHGG) (NCT04822805, 30/03/2021). METHODS: Eligible patients had a histological diagnosis of rHGG with first or subsequent recurrences. All patients received oral anlotinib 12 mg or 10 mg on days 1-14 (repeated every 21 days). In cases where brain magnetic resonance imaging examination revealed an increase in peritumoral edema without worsening of symptoms, patients received a temporary treatment of intravenous bevacizumab 10 mg/kg to alleviate edema. The primary endpoint was the median progression-free survival (mPFS), and the secondary endpoints included median overall survival (mOS), objective response rate (ORR), disease control rate (DCR), and safety. RESULTS: Twenty-five patients with rHGG were included in the efficacy and safety assessments. Eighteen patients received anlotinib alone, and seven patients received anlotinib in combination with Bev. For all patients, the mPFS and mOS were 5.0 months and 13.6 months, respectively. The ORR was 32%, and the DCR was 96%. It is noteworthy that the survival and response data of recurrent glioblastoma (rGBM) exhibit similarities to those of rHGG. For rGBM patients, there were no significant differences in mPFS, mOS, ORR, or DCR between the anlotinib alone and anlotinib + Bev groups. However, the incidence of treatment-related adverse events of any grade was higher in the anlotinib + Bev group compared to the anlotinib alone group (100% vs. 78%, p = 0.041). CONCLUSIONS: Both anlotinib alone and its combination with Bev demonstrated good efficacy and safety in the treatment of rHGG.

Metal-Ligand Bonds Based Reprogrammable and Re-processable Supramolecular Liquid Crystal Elastomer Network.

Dynamic covalent bonds endow liquid crystal elastomers (LCEs) with network rearrangeability, facilitating the fixation of mesogen alignment induced by external forces and enabling reversible actuation. In comparison, the bond exchange of supramolecular interactions is typically too significant to stably maintain the programmed alignment, particularly under intensified external stimuli. Nevertheless, the remaking and recycling of supramolecular interaction-based polymer networks are more accessible than those based on dynamic covalent bonds, as the latter are difficult to completely dissociate. Thus, preparing an LCE that possesses both supramolecular-like exchangeability and covalent bond-level stability remains a significant challenge. In this work, we addressed this issue by employing metal-ligand bonds as the crosslinking points of LCE networks. As such, mesogen alignment can be repeatedly encoded through metal-ligand bond exchange and stably maintained after programming, since the bond exchange rate is sufficiently slow when the programming and actuation temperatures are below the bond dissociation temperature. More importantly, the metal-ligand bonds can be completely dissociated at high temperatures, allowing the LCE network to be dissolved in a solvent and reshaped into desired geometries via solution casting. Building on these properties, our LCEs can be fabricated into versatile actuators, such as reversible folding origami, artificial muscles, and soft robotics.

Compact metalens-based integrated imaging devices for near-infrared microscopy.

With current trends to progressively miniaturize optical systems, it is now essential to look for alternative methods to control light at extremely small dimensions. Metalenses are composed of subwavelength nanostructures and have an excellent ability to manipulate the polarization, phase, and amplitude of incident light. Although great progress of metalenses has been made, the compact metalens-integrated devices have not been researched adequately. In the study, we present compact imaging devices for near-infrared microscopy, in which a metalens is exploited. The indicators including resolution, magnification, and image quality are investigated via imaging several specimens of intestinal cells to verify the overall performance of the imaging system. The further compact devices, where the metalens is integrated directly on the CMOS imaging sensor, are also researched to detect biomedical issues. This study provides an approach to constructing compact imaging devices based on metalenses for near-infrared microscopy, micro-telecopy, etc., which can promote the miniaturization tending of futural optical systems.

Radiomics Analysis Based on Multiparametric MRI for Predicting Early Recurrence in Hepatocellular Carcinoma After Partial Hepatectomy.

BACKGROUND: Preoperative prediction of early recurrence (ER) of hepatocellular carcinoma (HCC) plays a critical role in individualized risk stratification and further treatment guidance. PURPOSE: To investigate the role of radiomics analysis based on multiparametric MRI (mpMRI) for predicting ER in HCC after partial hepatectomy. STUDY TYPE: Retrospective. POPULATION: In all, 113 HCC patients (ER, n = 58 vs. non-ER, n = 55), divided into training (n = 78) and validation (n = 35) cohorts. FIELD STRENGTH/SEQUENCE: 1.5T or 3.0T, gradient-recalled-echo in-phase T1 -weighted imaging (I-T1 WI) and opposed-phase T1 WI (O-T1 WI), fast spin-echo T2 -weighted imaging (T2 WI), spin-echo planar diffusion-weighted imaging (DWI), and gradient-recalled-echo contrast-enhanced MRI (CE-MRI). ASSESSMENT: In all, 1146 radiomics features were extracted from each image sequence, and radiomics models based on each sequence and their combination were established via multivariate logistic regression analysis. The clinicopathologic-radiologic (CPR) model and the combined model integrating the radiomics score with the CPR risk factors were constructed. A nomogram based on the combined model was established. STATISTICAL TESTS: Receiver operating characteristic (ROC) curve analysis was used to evaluate the discriminative performance of each model. The potential clinical usefulness was evaluated by decision curve analysis (DCA). RESULTS: The radiomics model based on I-T1 WI, O-T1 WI, T2 WI, and CE-MRI sequences presented the best performance among all radiomics models with an area under the ROC curve (AUC) of 0.771 (95% confidence interval (CI): 0.598-0.894) in the validation cohort. The combined nomogram (AUC: 0.873; 95% CI: 0.756-0.989) outperformed the radiomics model and the CPR model (AUC: 0.742; 95% CI: 0.577-0.907). DCA demonstrated that the combined nomogram was clinically useful. DATA CONCLUSION: The mpMRI-based radiomics analysis has potential to predict ER of HCC patients after hepatectomy, which could enhance risk stratification and provide support for individualized treatment planning. EVIDENCE LEVEL: 4. TECHNICAL EFFICACY: Stage 4.

Quantification of Hepatic Fat Fraction in Patients With Nonalcoholic Fatty Liver Disease: Comparison of Multimaterial Decomposition Algorithm and Fat (Water)-Based Material Decomposition Algorithm Using Single-Source Dual-Energy Computed Tomography.

METHODS: Hepatic fat fractions were quantified by noncontrast (HFFnon-CE) and contrast-enhanced single-source dual-energy computed tomography in arterial phase (HFFAP), portal venous phase (HFFPVP) and equilibrium phase (HFFEP) using MMD in 19 nonalcoholic fatty liver disease patients. The fat concentration was measured on fat (water)-based images. As the standard of reference, magnetic resonance iterative decomposition of water and fat with echo asymmetry and least-squares estimation-iron quantification images were reconstructed to obtain HFF (HFFIDEAL-IQ). RESULTS: There was a strong correlation between HFFnon-CE, HFFAP, HFFPVP, HFFEP, fat concentration and HFFIDEAL-IQ (r = 0.943, 0.923, 0.942, 0.952, and 0.726) with HFFs having better correlation with HFFIDEAL-IQ. Hepatic fat fractions did not significantly differ across scanning phases. The HFFs of 3-phase contrast-enhanced computed tomography had a good consistency with HFFnon-CE. CONCLUSIONS: Hepatic fat fraction using MMD has excellent correlation with that of magnetic resonance imaging, is independent of the computed tomography scanning phases, and may be used as a routine technique for quantitative assessment of HFF.

Localized biphasic malignant mesothelioma presenting as a giant pelvic wall mass: a rare case report and literature review.

BACKGROUND: Localized biphasic MPeM is rare in clinical practice, we reviewed 8 cases of localized biphasic MPeM (including our present case), and summarized the clinical and imaging features of the disease. CASE PRESENTATION: We reported a 79-year-old man with chief complaint of a narrowing in the caliber of the stool for one year. A soft tissue shadow was occasionally found by CT examination in the right pelvic wall, and it was diagnosed as localized biphasic malignant peritoneal mesothelioma (MPeM) by postoperative pathology. Radical excision was performed and no radio-chemotherapy was applied. Nearly six years after surgery, the mass was significantly enlarged, and the neighboring tissues including rectum, prostate, seminal vesicle, and right ischial ramus were all infiltrated. The patient was in the end stage of cancer with poor prognosis. CONCLUSIONS: The localized biphasic MPeM may show following characteristics: (1) with heterogeneous low-density and obscure margin; (2) with low incidence rate of ascites; (3) with few central hemorrhage and necrosis; (4) with few calcified structures; (5) with mild to moderate heterogeneous delayed enhancement on contrast-enhanced CT. The imaging characteristics can provide further information for the diagnosis of localized biphasic MPeM in the future.

The value of single-source dual-energy CT imaging for discriminating microsatellite instability from microsatellite stability human colorectal cancer.

OBJECTIVES: To demonstrate the value of single-source dual-energy computed tomography (ssDECT) imaging for discriminating microsatellite instability (MSI) from microsatellite stability (MSS) colorectal cancer (CRC). METHODS: Thirty-eight and seventy-six patients with pathologically proven MSI and MSS CRC, respectively, were retrospectively selected and compared. These patients underwent contrast-enhanced abdominal ssDECT scans before any anti-cancer treatment. Effective atomic number (Eff-Z) in precontrast phase, slope k of spectral HU curve in precontrast (k-P), arterial (k-A), venous (k-V), and delayed phase (k-D), normalized iodine concentration in arterial (NIC-A), venous (NIC-V), and delayed phase (NIC-D), of tumors in two groups were measured by two reviewers. Consistency of measurements was tested by intra-class correlation coefficients (ICC). Mann-Whitney U test or Student's t test was used to compare above values between MSI and MSS. Multivariate logistic regression was used to analyze multiple parameters. Receiver operating characteristic curves were calculated to assess diagnostic efficacies. RESULTS: Interobserver agreement was excellent (ICC > 0.80). MSI CRC had significantly lower values in all measurements (NIC-A, V, D; k-P, A, V, D; Eff-Z) than MSS CRC. For discriminating MSI from MSS CRC, the area under curve (AUC) using k-A was the highest (AUC, 0.803; sensitivity, 72.4%; specificity, 76.3%). The multivariate logistic regression (selection method, Enter) with combined ssDECT parameters (NIC-A, NIC-V, NIC-D, Eff-Z, k-P, k-A, k-V, k-D) significantly improved diagnostic capability with AUC of 0.886 (sensitivity, 81.6%; specificity, 81.6%). CONCLUSIONS: The combination of multiple parameters in ssDECT imaging by multivariate logistic regression provides relatively high diagnostic accuracy for discriminating MSI from MSS CRC. KEY POINTS: • ssDECT generates multiple parameters for discriminating CRC with MSI from MSS. • ssDECT measurements for MSI CRC were significantly lower than MSS CRC. • Combination of ssDECT parameters further improves diagnostic capability for differentiation.

Radiomics-based classification of hepatocellular carcinoma and hepatic haemangioma on precontrast magnetic resonance images.

BACKGROUND: To evaluate the feasibility of using radiomics with precontrast magnetic resonance imaging for classifying hepatocellular carcinoma (HCC) and hepatic haemangioma (HH). METHODS: This study enrolled 369 consecutive patients with 446 lesions (a total of 222 HCCs and 224 HHs). A training set was constituted by randomly selecting 80% of the samples and the remaining samples were used to test. On magnetic resonance (MR) images of HCC and HH obtained with in-phase, out-phase, T2-weighted imaging (T2WI), and diffusion-weighted imaging (DWI) sequences, we outlined the target lesions and extracted 1029 radiomics features, which were classified as first-, second-, higher-order statistics and shape features. Then, the variance threshold, select k best, and least absolute shrinkage and selection operator algorithms were explored for dimensionality reduction of the features. We used four classifiers (decision tree, random forest, K nearest neighbours, and logistic regression) to identify HCC and HH on the basis of radiomics features. Two abdominal radiologists also performed the conventional qualitative analysis for classification of HCC and HH. Diagnostic performances of radiomics and radiologists were evaluated by receiver operating characteristic (ROC) analysis. RESULTS: Valuable radiomics features for building a radiomics signature were extracted from in-phase (n = 22), out-phase (n = 24), T2WI (n = 34) and DWI (n = 24) sequences. In comparison, the logistic regression classifier showed better predictive ability by combining four sequences. In the training set, the area under the ROC curve (AUC) was 0.86 (sensitivity: 0.76; specificity: 0.78), and in the testing set, the AUC was 0.89 (sensitivity: 0.822; specificity: 0.714). The diagnostic performance for the optimal radiomics-based combined model was significantly higher than that for the less experienced radiologist (2-years experience) (AUC = 0.702, p < 0.05), and had no statistic difference with the experienced radiologist (10-years experience) (AUC = 0.908, p>0.05). CONCLUSIONS: We developed and validated a radiomics signature as an adjunct tool to distinguish HCC and HH by combining in-phase, out-phase, T2W, and DW MR images, which outperformed the less experienced radiologist (2-years experience), and was nearly equal to the experienced radiologist (10-years experience).

Growth mechanism of one-step self-masking reactive-ion-etching (RIE) broadband antireflective and superhydrophilic structures induced by metal nanodots on fused silica.

This work presents a low-cost, simple, convenient, advanced technology to prepare large-area defect-free subwavelength structures (SWSs). SWSs were obtained by a metal-induced one-step self-masking RIE process on a fused-silica surface, in which metal-fluoride (mainly ferrous-fluoride) nanodots were used to induce and gather stable fluorocarbon polymer etching inhibitors in the RIE polymers as masks. The SWS growth processes are visible with an increase in etching time and some exhibit prominent broadband antireflective properties from the visible to the near-infrared wavelength range. Transmission in the 600-900-nm range increased from approximately 93% for the polished fused silica to above 99% for the double-side SWSs on fused silica. A theoretical simulation by a finite-difference time-domain method agreed well with the experiments. Moreover, the surface of the SWSs exhibits excellent superhydrophilic properties.

EGCG protects against homocysteine-induced human umbilical vein endothelial cells apoptosis by modulating mitochondrial-dependent apoptotic signaling and PI3K/Akt/eNOS signaling pathways.

Homocysteine (Hcy) induced vascular endothelial injury leads to the progression of endothelial dysfunction in atherosclerosis. Epigallocatechin gallate (EGCG), a natural dietary antioxidant, has been applied to protect against atherosclerosis. However, the underlying protective mechanism of EGCG has not been clarified. The present study investigated the mechanism of EGCG protected against Hcy-induced human umbilical vein endothelial cells (HUVECs) apoptosis. Methyl thiazolyl tetrazolium assay (MTT), transmission electron microscope, fluorescent staining, flow cytometry, western blot were used in this study. The study has demonstrated that EGCG suppressed Hcy-induced endothelial cell morphological changes and reactive oxygen species (ROS) generation. Moreover, EGCG dose-dependently prevented Hcy-induced HUVECs cytotoxicity and apoptotic biochemical changes such as reducing mitochondrial membrane potential (MMP), decreasing Bcl-2/Bax protein ratio and activating caspase-9 and 3. In addition, EGCG enhanced the protein ratio of p-Akt/Akt, endothelial nitric oxide synthase (eNOS) activation and nitric oxide (NO) formation in injured cells. In conclusion, the present study shows that EGCG prevents Hcy-induced HUVECs apoptosis via modulating mitochondrial apoptotic and PI3K/Akt/eNOS signaling pathways. Furthermore, the results indicate that EGCG is likely to represent a potential therapeutic strategy for atherosclerosis associated with Hyperhomocysteinemia (HHcy).

Combination of reaction ion etching and dynamic chemical etching for improving laser damage resistance of fused silica optical surfaces.

In this Letter, an effective combined process of reaction ion etching (RIE) and dynamic chemical etching (DCE) is applied for significantly improving the damage resistance of fused silica optics, while minimizing the removal amount. By optimizing the combination process and removal depth, a near-perfect optical surface of fused silica with relatively low roughness (<0.7 nm) is created with 1 µm RIE pretreatment and 3 µm DCE retreatment. In this case, the sample has a 2.4 times enhanced 0% probability damage threshold compared to the original sample. We show that the optimized combining process with a low removal amount is superior to a conventional HF-based etching process with a high removal amount in enhancing damage resistance and controlling the surface shape and roughness of fused silica. The results advance our understanding of a key factor influencing the RIE-DCE matching relationship and can lead to further optimization of associated applications, ranging from material processing to high-power laser systems.

Phosphocreatine protects endothelial cells from oxidized low-density lipoprotein-induced apoptosis by modulating the PI3K/Akt/eNOS pathway.

Endothelial apoptosis triggered by oxidized low-density lipoprotein (oxLDL) can accelerate the progression of endothelial dysfunction atherosclerosis. Phosphocreatine (PCr) is a natural compound, which has been used in cardiac disease and cardiopulmonary resuscitation. However, its protective effects on atherosclerosis and its mechanism have not been clarified. In the present study, we investigated the anti-apoptotic effect of phosphocreatine in human umbilical vein endothelial cells (HUVECs) exposed to oxLDL and explored the possible mechanisms. HUVECs were pre-treated with 10-30 mM PCr and then stimulated with oxLDL. Cell morphology, cytotoxicity and apoptosis were evaluated by light microscopy, CCK assay, and flow cytometry respectively. Levels of Bax, Bcl-2, protein expression of protein kinase B (Akt), eNOS and caspase activities were assessed by Western blotting. Reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were measured with fluorescent probes. Lactate dehydrogenase (LDH), malondialdehyde (MDA), nitric oxide (NO) and superoxide dismutase (SOD) contents were determined by spectrophotometer. Our results showed that PCr dose-dependently prevented oxLDL associated HUVEC cytotoxicity and apoptotic biochemical changes such as loss of MMP, LDH and MDA leakage and loss of SOD, decrease of Bcl-2/Bax protein ratio, activation of caspase-3 and 9, and ROS generation. In addition, the antiapoptotic effect of PCr was partially inhibited by a PI3K inhibitor (LY294002) and also enhanced p-Akt/Akt protein ratio, eNOS activation and NO production. In conclusion, our data show that the inhibition of oxLDL-induced endothelial apoptosis by PCr is due, at least in part to its anti-oxidant activity and its ability to modulate the PI3K/Akt/eNOS signaling pathway.

SZC017, a novel oleanolic acid derivative, induces apoptosis and autophagy in human breast cancer cells.

Oleanolic acid (OA) and its derivatives such as 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO), CDDO-Me, and CDDO-Im show potent anticancer function. In this study, we elucidated the anticancer effect of SZC017, a novel OA derivative and identified the mechanisms by which SZC017 induces MCF-7 cell death. We found that SZC017 effectively decreased the cell viability of these breast cancer cells, but was less toxic to MCF10A mammary epithelial cells. Mechanisms underlying the inhibition of cell viability are apoptosis, autophagy induction, and G0/G1 phase arrest. SZC017 treatment suppressed the levels of Akt, phosphorylated-Akt (p-Akt), p-IκBα, total p65, and total p-p65, in addition to p-p65 in both the cytoplasm and nucleus. Furthermore, the inhibition of p65 nuclear translocation was confirmed by immunofluorescence staining. Cell viability was increased after pretreatment with chloroquine, an inhibitor of autophagy, whereas the level of procaspase-3 was significantly decreased. A concentration-dependent increase in the intracellular reactive oxygen species (ROS) level was observed in both MCF-7 and MDA-MB-231 cells. Additionally, pretreatment with N-acetyl-L-cysteine (NAC), a ROS scavenger, increased cell viability and the expression of Akt and procaspase-3, but decreased the ratio of LC3-II/I. These data show that SZC017 is an effectively selective anticancer agent against breast cancer cells, highlighting the potential use of this derivative as a breast cancer therapeutic agent.

Rapid discrimination of urine specific gravity using spectroscopy and a modified combination method based on SPA and spectral index.

To achieve high-accuracy urine specific gravity discrimination and guide the design of four-waveband multispectral sensors. A modified combination strategy was attempted to be proposed based on the successive projections algorithm (SPA) and the spectral index (SI) in the present study. First, the SPA was used to select four spectral variables in the full spectra. Second, the four spectral variables were mathematically transformed by SI to obtain SI values. Then, SPA gradually fusions the SI values and establishes models to identify USG. The results showed that the SPA can screen out the four characteristic wavelengths related to the measured sample attributes. SIs can be used to improve the performance of constructed prediction models. The best model only involves four spectral variables and 1 SI value, with high accuracy (91.62%), sensitivity (0.9051), and specificity (0.9667). The results reveal that m-SPA-SI can effectively distinguish USG and provide design guidance for 4-wavelength multispectral sensors.

Combination of site-directed mutagenesis and calcium ion addition for enhanced production of thermostable MBP-fused heparinase I in recombinant Escherichia coli.

Heparinase I (HepI), which specifically cleaves heparin and heparan sulfate, is one of the most extensively studied glycosaminoglycan lyases. Low productivity of HepI has largely hindered its industrial and pharmaceutical applications. Loss of bacterial HepI enzyme activity through poor thermostability during its expression and purification process in production can be an important issue. In this study, using a thermostabilization strategy combining site-directed mutagenesis and calcium ion addition during its production markedly improved the yield of maltose-binding protein-fused HepI (MBP-HepI) from recombinant Escherichia coli. Substitution of Cys297 to serine in MBP-HepI offered a 30.6% increase in the recovered total enzyme activity due to a mutation-induced thermostabilizing effect. Furthermore, upon addition of Ca2+ as a stabilizer at optimized concentrations throughout its expression, extraction, and purification process, purified mutant MBP-HepI showed a specific activity of 56.3 IU/mg, 206% higher than that of the wild type obtained without Ca2+ addition, along with a 177% increase in the recovered total enzyme activity. The enzyme obtained through this novel approach also exhibited significantly enhanced thermostability, as indicated by both experimental data and the kinetic modeling. High-yield production of thermostable MBP-HepI using the present system will facilitate its applications in laboratory-scale heparin analysis as well as industrial-scale production of low molecular weight heparin as an improved anticoagulant substitute.

DLP 3D printed hydrogels with hierarchical structures post-programmed by lyophilization and ionic locking.

Porous hydrogels have been intensively used in energy conversion and storage, catalysis, separation, and biomedical applications. Controlling the porosity of these materials over multiple length scales brings about new functionalities and higher efficiency but is a challenge using the current manufacturing methods. Herein we developed a post-programming method to lock the lyophilized pores of 3D printed hydrogels as an experimental platform towards hierarchically structured pores. 3D printing endows the hydrogels with arbitrary 3D geometries and controllable pores at the millimeter length scale. Lyophilization and ionic crosslinking of the as-printed hydrogel networks are conducted as a post-programming process which results in pores at micrometer length scales beyond the printing resolution. Utilizing this combined manufacturing technology, 3D hydrogel lattices with tunable porosities and mechanical properties can be created, which are further exploited for efficient solar vapor generation.

3D printing of dynamic covalent polymer network with on-demand geometric and mechanical reprogrammability.

Delicate geometries and suitable mechanical properties are essential for device applications of polymer materials. 3D printing offers unprecedented versatility, but the geometries and mechanical properties are typically fixed after printing. Here, we report a 3D photo-printable dynamic covalent network that can undergo two independently controllable bond exchange reactions, allowing reprogramming the geometry and mechanical properties after printing. Specifically, the network is designed to contain hindered urea bonds and pendant hydroxyl groups. The homolytic exchange between hindered urea bonds allows reconfiguring the printed shape without affecting the network topology and mechanical properties. Under different conditions, the hindered urea bonds are transformed into urethane bonds via exchange reactions with hydroxyl groups, which permits tailoring of the mechanical properties. The freedom to reprogram the shape and properties in an on-demand fashion offers the opportunity to produce multiple 3D printed products from one single printing step.

Multishape Programming of Shape Memory Polymer Assemblies Fabricated by Vat Photopolymerization-Based 3D Printing and Interfacial Welding.

The combination of three-dimensional (3D) printing and shape memory polymers (SMP) enables programmable shape morphing of complex 3D structures, which is commonly termed four-dimensional (4D) printing. The process requirements of vat photopolymerization-based 3D printing impose limitations on the molecular structure design of SMPs, making it challenging to achieve triple- or multiple-shaped memory effects. Herein, we printed SMPs with different Tg values and obtained an SMP assembly through interfacial welding. The welding process is facilitated by the dynamic exchange of hindered urethane bonds at the interface. The resulting SMP assembly exhibits a quadruple shape memory effect, enabling programmable sequential deformation. The advantage of this approach is that the molecular design and the corresponding thermodynamic properties of different welding SMP components can be independently adjusted, enabling a greater range of shape and functional variations in the final 3D SMP assembly.

3D printing of self-healing personalized liver models for surgical training and preoperative planning.

3D printing can produce intuitive, precise, and personalized anatomical models, providing invaluable support for precision medicine, particularly in areas like surgical training and preoperative planning. However, conventional 3D printed models are often significantly more rigid than human organs and cannot undergo repetitive resection, which severely restricts their clinical value. Here we report the stereolithographic 3D printing of personalized liver models based on physically crosslinked self-healing elastomers with liver-like softness. Benefiting from the short printing time, the highly individualized models can be fabricated immediately following enhanced CT examination. Leveraging the high-efficiency self-healing performance, these models support repetitive resection for optimal trace through a trial-and-error approach. At the preliminary explorative clinical trial (NCT06006338), a total of 5 participants are included for preoperative planning. The primary outcomes indicate that the negative surgery margins are achieved and the unforeseen injuries of vital vascular structures are avoided. The 3D printing of liver models can enhance the safety of hepatic surgery, demonstrating promising application value in clinical practice.