Microporous organic hydroxyl-functionalized polybenzotriazole for encouraging CO2 capture and separation

We report a mild, hydroxyl functionalized and thermal stable benzotriazole-based aerogel (HO-PBTA), which is inspired by phenolic resin chemistry. Taking advantage of the synergistic adsorption interactions between hydroxy-benzotriazole and CO₂, and the phobic effect between benzotriazole and nitrogen (N₂), the CO₂ uptake capacity of the HO-PBTA reaches an encouraging level (6.41 mmol g⁻¹ at 1.0 bar and 273 K) with high selectivity (CO₂/N₂ = 76 at 273 K).

We report a mild, hydroxyl functionalized and thermal stable benzotriazole-based aerogel (HO-PBTA), which is inspired by phenolic resin chemistry.

Nowadays, global warming caused by increased concentrations of carbon dioxide (CO₂) in the atmosphere is one of the most serious environmental problems.^1–3 The development of novel functional materials and new technologies for CO₂ capture and storage has gained great attention. Microporous organic polymers (MOPs) with intrinsic properties including large specific surface area, narrow pore size distribution, good chemical stability, and low skeleton density have exhibited potential applications in gas storage and separation.^4–7 In addition, microporous porous materials with excellent intrinsic properties also made significant breakthroughs in liquid separation.^8,9 The structure and CO₂ adsorption of the MOPs have complicated relationships. Therefore, the design of high performance CO₂ capture materials often involves sophisticated molecular design and careful adjustments of the ingredient ratio. It has been shown that the incorporation of N-containing groups into the pore wall of MOPs has a profound impact on both CO₂ uptake and selectivity by enhancing their physisorption interactions,^10–15 however, it still remains a great challenge to make a facile synthesis of functional MOP materials that capture CO₂ efficiently and selectively.In the application of CO₂ capture, the nitrogen-containing MOPs act as capable storage media due to physisorption that involves an electron donor–acceptor mechanism between a heteroatom nitrogen and CO₂ on the inner surface of the networks.^16–18 The first principles study indicated that nitrogen-containing heteroaromatic groups can form strong physical interactions with CO₂via “dispersive π–π stacking” and electrostatic “in-plane” mechanisms.¹⁹ This theoretical calculation guides us how to design the functional materials that capture CO₂ efficiently and selectively. In previous work, we described a new strategy for CO₂ capture based on the synergistic effect of electrostatic in-plane and dispersive π–π stacking interactions of two functional groups with CO₂, and the proposed synergistic effect can be considered as a new rationale for the design and fabrication of CO₂ capture materials.²⁰ In addition, it has been demonstrated that azo-functionalized MOPs exhibit the N₂ phobicity due to the entropic loss of N₂ gas molecules upon binding, which endows the networks with the unprecedented CO₂ selectivity.²¹ Inspired by these reported studies, we hypothesized that both the CO₂ adsorption capacity and CO₂/N₂ selectivity can be improved greatly by involving multiple, more than two, functional groups in MOP networks where multiple mechanisms work for CO₂ capture and separation. In this work, the synergistic adsorption interactions between the HO-PBTA polymer and CO₂ molecules, the N₂-phobic effect between the HO-PBTA polymer and N₂ have been investigated in details. It is expected that the comprehensive effects of the CO₂-philic and N₂-phobic behaviors will provide new design principles for the development of next-generation functional porous polymers with high CO₂ adsorption capacity and selectivity.To achieve this objective, a benzotriazole-based microporous aerogel (HO-PBTA), with azo, hydroxyl and imino groups in the polymer chains, was fabricated via sol–gel technology involving phenolic resin-inspired chemistry^22–24 and followed by CO₂ supercritical drying (Fig. 1A). The material preparation and characterization are detailed in the ESI.^† The as-prepared HO-PBTA is a dark gray, porous ultralight material, as shown in Fig. 1B. HO-PBTA aerogel was characterized by Fourier transform infrared and ¹³C CP/MAS NMR, and the results were in good agreement with the proposed structures (Fig. 2). The FTIR spectrum of the HO-PBTA is shown in Fig. 2a, in which the absorption peaks at about 3190 cm⁻¹ and 3402 cm⁻¹ correspond to the structure of NH and the OH groups. The peak at 1618 cm⁻¹ is attributed to the vibration of the aromatic ring skeleton. And the absorption at 1536 cm⁻¹ corresponds to the structure of C N in the network. As shown in Fig. 2B, the broad peaks at 150–110 ppm are ascribed to the benzotriazole group carbons, and the peaks at 75–25 ppm corresponds to methylene carbons.Open in a separate windowFig. 1Synthesis of HO-PBTA aerogel. (A) Dark gray aerogel of HO-PBTA was obtained by reacting 4-hydroxy-1H-benzotriazole with formaldehyde, in water at 80 °C in the presence of potassium hydroxide under air conditions; (B) the photograph of the HO-PBTA aerogel.Open in a separate windowFig. 2Chemical structure characterization of the HO-PBTA polymer material. (A) FTIR spectrum, recorded as KBr pellet; (B) ¹³C CP/MAS NMR spectrum.The porosity of the HO-PBTA aerogel was quantified by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and sorption analysis. A SEM image shows that the HO-PBTA aerogel consists of aggregated particles with submicrometer sizes (Fig. 3A). The TEM image (Fig. 3B) reveals the micropore structure, which is an essential requirement for CO₂ capture. The porosity of aerogel was further quantified by sorption analysis using nitrogen (N₂) as the sorbate molecule, and the HO-PBTA aerogel is microporous and exhibits a combination of type I and II N₂ sorption isotherms according to the IUPAC classification (Fig. 4A).²⁵ The increase in the nitrogen sorption at a high relative pressure above 0.9 may arise in part from interparticulate porosity associated with the meso- and macrostructures of the samples and interparticular void.²⁶ According to ref. 27, the specific surface areas calculated in the relative pressure (P/P₀) range from 0.01 to 0.1 shows that the Brunauer–Emmett–Teller (BET) specific surface area of HO-PBTA is up to 2160 m² g⁻¹ (Fig. S3^†). The pore size distribution (PSD) of the network calculated from the adsorption branch of the isotherms with the nonlocal density functional theory (NLDFT) approach indicates that HO-PBTA aerogel exhibits a dominant pore diameter centered at about 0.60 nm (inset in Fig. 4A). Thermal property of HO-PBTA aerogel was evaluated via thermogravimetric analysis (TGA) in nitrogen and air conditions, and the typical TGA curves are shown in Fig. S4.^† HO-PBTA exhibits great thermal stability with high decomposition temperature (T_d, 5% = ∼500 °C) at N₂ atmosphere. The TGA curve indicated that the HO-PBTA aerogel still exhibited good thermal stability at air condition.Open in a separate windowFig. 3Microstructural characterization of HO-PBTA aerogel. (A) Scanning electron microscopy (SEM) image of HO-PBTA aerogel; (B) transmission electron microscopy (TEM) image of HO-PBTA aerogel.Open in a separate windowFig. 4(A) Nitrogen adsorption–desorption isotherms and the pore size distribution calculated by the nonlocal density functional theory (inset) of HO-PBTA aerogel. (B) Gas adsorption isotherms of HO-PBTA aerogel at 273 K.The CO₂ adsorption capacity and selectivity (CO₂/N₂) in HO-PBTA aerogel were evaluated by adsorption isotherm measurements. As shown in Fig. 4B, the CO₂ capture exhibits an increase with the increasing of the pressure. The CO₂ adsorption capacity of the HO-PBTA aerogel is as high as 6.41 mmol g⁻¹ at 1.0 bar and 273 K, while the adsorption capacity of N₂ is only 0.09 mmol g⁻¹ at the same conditions (inset in Fig. 4B). The CO₂ adsorption capacity of the HO-PBTA aerogel is up to 2.3 mmol g⁻¹ at 1 bar and 323 K, and 0.02 mmol g⁻¹ for N₂ at the same conditions (Fig. S5^†). Equilibrium CO₂ adsorption capacity is found to decrease with an increase in temperature due to the exothermic nature of the adsorption process, as expected for physical adsorbents. We found that the CO₂ adsorption capacity of the HO-PBTA aerogel is higher than most of the CO₂ capture MOP materials, and close to some of the MOF materials (Table S1^†).^28–30 This high affinity is a consequence of the favourable interactions of the polarizable CO₂ molecules through multiple adsorption interactions with the framework, and also the inherent microporosity of HO-PBTA aerogel. Additionally, HO-PBTA aerogel also has great CO₂ adsorption capacities and selectivities at 298 and 323 K (Fig. S5^†), and these values are still comparable to the high surface area MOP networks.^31–33For the further CO₂ adsorption, CO₂ was also adsorbed preferentially over N₂ at high temperatures. The selectivities were calculated using the Ideal Adsorbed Solution Theory (IAST) for CO₂/N₂ mixture in the ratio of 0.15 : 0.85. At 1 bar, the IAST CO₂/N₂ selectivities of the HO-PBTA were 76 at 273 K, 97 at 298 K and become 110 at 323 K, which close to the highest one reported to date under the same conditions. Additionally, the HO-PBTA aerogel have the high selectivity of CO₂/N₂ at high temperature than other porous materials (Table S2^†). It is worth noting that the CO₂/N₂ selectivities increased with the temperature increasing, which are essential requirements for high temperature post-combustion CO₂ adsorption. N₂ uptake drops ∼70% at a temperature increase from 273 to 298 K, compared with a ∼60% drop for CO₂. This phenomenon is in line with the conventional CO₂ affinity and the concept of N₂ phobic in nitrogen-rich porous polymers where nitrogen-rich groups (–N N–) will reject N₂ gas selectively.²¹ To further akin to capture from post-combustion gas streams, CO₂ adsorption capacity of HO-PBTA aerogel at higher temperature have been characterized (Fig. S6^†). The HO-PBTA shown the good CO₂ adsorption capacity of 1.8 mmol g⁻¹ at 333 K and 1.5 mmol g⁻¹ 343 K. The N₂ uptakes of HO-PBTA aerogel under the same conditions were 0.016 mmol g⁻¹ and 0.015 mmol g⁻¹, resulting in selectivity of 112 and 101, respectively.The isosteric heat of adsorption (Q_st) for HO-PBTA aerogel was calculated using the virial equations.³⁴ As shown in Fig. S7,^† HO-PBTA has a Q_st value of 33.9 kJ mol⁻¹, and this value can be considered as the optimum for gas adsorption and separation because of a balance between the reversibility and selectivity. The Q_st values is highest among reported values for organic porous polymers and comparable to some MOFs compounds.^21,35,36 The impressive Q_st of 33.9 kJ mol⁻¹ further indicates the strong interaction of HO-PBTA polymers with CO₂ guest molecules. It should be noted that the higher and more optimized Q_st value of the HO-PBTA aerogel can be ascribed to the synergistic effect of azo (–N N–), hydroxyl (–OH) and imino (–NH) units arising from different interaction mechanisms.To illustrate the synergistic adsorption mechanism, we used density functional theory (DFT)^{19,20,37–39} to investigate the interaction of HO-PBTA with CO₂ and to track the CO₂ capture process. The calculation is detailed in the ESI. Fig. 5 shows a series of snapshots for CO₂ capture by 4-hydroxybenzotriazole, as the model compound, where benzotriazole and hydroxyl work synergistically to adsorb multiple CO₂ molecules. The minimum energy structure of the CO₂–azo complex is obtained when CO₂ lies on the azo at a bond distance of 3.06 Å to form the π–π stacking conformation (Fig. 5B). The electrostatic “in-plane” equilibrium conformation of CO₂–HO-PBTA involves two sites: one is the electron deficient central carbon atom of CO₂ to the lone pair of electrons on a nitrogen atom of azo group via dipole–quadrupole interaction; the other is lone pairs of oxygen on CO₂ to a hydrogen atom on the imino group (or a hydrogen atom on the hydroxyl) via hydrogen bonding (Fig. 5C and F). Either dipole–quadrupole interaction or hydrogen bonding cannot stabilize the CO₂–HO-PBTA complex because of their low binding energies.¹⁹ However, previous works and our calculation indicated that simultaneous formation of dipole–quadrupole interaction and hydrogen bonding at both sites cause a much more stable in-plane conformation of CO₂–HO-PBTA complex (Fig. S8^†).^19,20 However, the capture of flowing CO₂ by electrostatic “in-plane” interactions is difficult due to a small binding area by only two atomistic sites. On the other hand, CO₂ can be rapidly adsorbed on the azo group because of its relatively large binding area (Fig. 5A). To our knowledge, the desorption occurs frequently driven by thermal fluctuation. Once CO₂ desorption, the starting speed should be much slower than the bulk speed, resulting in a high probability to be captured by an adjacent hydroxyl and imino groups. The in-plane conformation of CO₂–HO-PBTA complex is, therefore, formed much easily and efficiently with help of the functional azo while retaining the high selectivity of CO₂ over other gas molecules (Fig. 5H). Final coordinates of DFT geometry optimization was shown in Table S3.^†Open in a separate windowFig. 5DFT results to track the full CO₂ capture process. (A) A CO₂ molecule is adsorbed on the face of an electron-rich azo group via the dispersive π–π stacking interaction. (B and C) The desorbed CO₂ molecule can be captured by an adjacent hydroxyl, a stable “electrostatic in-plane” conformation including dipole–quadrupole and hydrogen bond interactions is formed. (D) The second CO₂ molecule comes close to the azo group, (E) and the CO₂ molecule is adsorbed on the azo group. (F) The desorbed CO₂ molecule can be captured by an adjacent imino group. (G) The third CO₂ molecule comes close to the azo group, (H) and the CO₂ molecule is adsorbed on the azo group. The gray, white, blue and red spheres represent C, H, N, and O atoms, respectively.     

Retention in Care and Viral Suppression Among Persons Living With HIV/AIDS in New York City, 2006–2010

Objectives. We estimated the proportions of persons living with HIV/AIDS (PLWHA) in New York City (NYC) retained in care and virally suppressed.Methods. We used routinely reported laboratory surveillance data to measure trends in retention in care and viral suppression in PLWHA in NYC from 2006 through 2010. Our denominator excluded persons lacking any HIV-related laboratory tests during the 5 years prior to the year of analysis.Results. The proportion of patients retained in care (≥ 1 care visit in a calendar year) was stable, at 82.5% in 2006 and 81.8% in 2010. However, the proportion of persons with evidence of viral suppression increased significantly, from 44.3% to 59.1%. Blacks were least likely to have viral suppression (adjusted prevalence ratio [APR] = 0.89; 95% confidence interval [CI] = 0.87, 0.90). A U-shaped relationship between age and viral suppression was observed, with the 20- to 29-year age group least likely to have a suppressed viral load.Conclusions. Higher and more plausible proportions retained in care and virally suppressed than national estimates may reflect the difference in methodology and our comprehensive HIV-related laboratory reporting system.Suppression of viremia in HIV-infected persons is associated with improvements in morbidity and mortality and reduced transmission to uninfected partners.1–6 The US Department of Health and Human Services Panel on Antiretroviral Guidelines for Adults and Adolescents recommends that all patients with HIV undergo regular monitoring of disease status and be treated with antiretroviral therapy (ART).7 However, despite the wide availability of HIV care services in the United States, many HIV-infected persons are not engaged in regular care or receiving ART.8–11The US National HIV/AIDS Strategy (NHAS) has set many goals, among which are an increase in the proportion of newly diagnosed patients linked to clinical care, the proportion of diagnosed patients receiving regular HIV care, and the proportion achieving and maintaining viral suppression.12 HIV surveillance data routinely reported by state and local health departments to the Centers for Disease Control and Prevention (CDC) have been used to evaluate local and national progress toward meeting the goals.13–16The CDC recently estimated that among persons living with HIV/AIDS (PLWHA), 45% were retained in care, 40% were prescribed ART, and 31% had a suppressed viral load (≤ 200 copies/mL).17 These estimates were surprisingly low considering the natural history of HIV and wide availability of HIV care in the United States.18–23 The CDC estimate of diagnosed patients receiving ART in the United States was even lower than the global average, 40% in the United States versus 47% worldwide (more than 8 million out of 17 million).24Monitoring local progress toward meeting the NHAS goals requires accurate estimates, backed up by complete, high-quality data and generated by appropriate methods. In this analysis, we used New York City (NYC) HIV diagnosis and laboratory surveillance data to estimate the proportions of HIV patients retained in care and virally suppressed in NYC from 2006 through 2010.     

Genome-wide analysis of DNA 5-hmC in peripheral blood of uremia by hMeDIP-chip

Background: Treatment of uremia is now dominated by dialysis; in some cases, patients are treated with dialysis for decades, but overall outcomes are disappointing. A number of studies have confirmed the relevance of several experimental insights to the pathogenesis of uremia, but the specific biomarkers of uremia have not been fully elucidated. To date, our knowledge about the alterations in DNA 5-hydroxymethylcytosine (5-hmC) in uremia is unclear, to investigate the role of DNA 5-hmC in the onset of uremia, we performed hMeDIP-chip between the uremia patients and the normal controls from the experiment to identify differentially expressed 5-hmC in uremia-associated samples. Methods: Extract genomic DNA, using hMeDIP-chip technology of Active Motif companies for the analysis of genome-wide DNA 5-hmC, and quantitative real-time PCR confirmation to identify differentially expressed 5-hmC level in uremia-associated samples. Results: There were 1875 genes in gene Promoter, which displayed significant 5-hmC differences in uremia patients compared with normal controls. Among these genes, 960 genes displayed increased 5-hmC and 915 genes decreased 5-hmC. 4063 genes in CpG Islands displayed significant 5-hmC differences in uremia patients compared with normal controls. Among these genes, 1780 genes displayed increased 5-hmC and 2283 genes decreased 5-hmC. Three positive genes, HMGCR, THBD, and STAT3 were confirmed by quantitative real-time PCR. Conclusion: Our studies indicate the significant alterations of 5-hmC. There is a correlation of gene modification 5-hmC in uremia patients. Such novel findings show the significance of 5-hmC as a potential biomarker or promising target for epigenetic-based uremia therapies.     

一站式杂交手术与全弓置换治疗主动脉弓病变的疗效分析

目的探讨一站式杂交手术与全弓置换处理主动脉弓部病变的疗效。方法回顾性分析2017年1月至2019年4月我院收治的29例累及主动脉弓部病变患者的临床资料,将13例行一站式杂交手术的患者纳入杂交手术组,16例行全弓置换联合支架象鼻的患者纳入全弓置换组。比较2组患者肺部感染、胸腔积液、肾损伤、神经系统损伤、心功能不全、截瘫、切口感染、用血量和住院时间等情况。结果所有患者均成功完成手术。术后2组患者肺部感染、胸腔积液、一过性肾功能损伤、切口感染、一过性意识障碍、截瘫、脑梗死/脑出血、心功能不全、移植旁路血管再发狭窄、再发主动脉夹层等术后并发症发生率比较,差异无统计学意义(P>0.05);2组患者住院时间比较,差异无统计学意义(P>0.05);杂交手术组患者用血量平均(3.69±2.89)U,全弓置换组平均(12.38±3.14)U,组间比较差异有统计学意义(P<0.05)。杂交手术组围手术期因突发心跳骤停,成功复苏后脑死亡1例,全弓置换组无围手术期死亡病例。随访1~26个月,随访期间杂交手术组出现1例覆膜支架远端夹层扩张破裂死亡病例,全弓置换组出现1例脑血管意外导致呼吸功能衰竭死亡病例,其余患者恢复良好。结论一站式杂交手术与全弓置换治疗弓部病变效果均满意,其中一站式杂交手术用血量较全弓置换组明显减少,无需深低温停循环,对年龄大、一般情况差的患者更为有利;而全弓置换组用血量更大,需要停循环、创伤大,但象鼻支架材料利于二次手术根治远端病变,适用于年轻、术前一般情况良好的患者。     

纳米羟基磷灰石/聚酰胺66支撑棒结合同种异体骨治疗ARCOⅢ期股骨头坏死

BACKGROUND: It remains controversial whether patients with ARCO stage III osteonecrosis of the femoral head should be treated with femoreal head preserving surgery, and what the clinical efficacy of femoreal head preserving surgery is.     

全内镜下腰椎板开窗减压有限元模拟建模及生物力学变化

文题释义： 腰椎有限元手术模拟建模：模型首先通过获取人体腰椎CT资料,以DICOM格式导入Mimics软件中建立L_4-5模型,再运用3-matic建立椎间盘和手术模型。将建好的模型进行网格划分,在Ansysworkbench 18.0中进行材料赋值及韧带添加,同时进行相关力学分析。 腰椎管狭窄症：是指由于腰椎中央管、侧隐窝及椎间孔的直径减少而导致的临床综合征,主要发生于65岁以上的老年人,主要病因包括椎间盘退变、小关节退变、退变性滑脱、退变性腰椎畸形等,进而引起以下腰痛及神经源性间歇性跛行为主的临床症状。 背景：全内镜下减压有效治疗腰椎管狭窄症为突破性前沿技术,相对于开放手术具有创伤小、操作可控、并发症少的特点,但其有限元力学分析鲜有报道。 目的：建立全内镜下腰椎椎板开窗有限元模型并探讨减压范围及髓核摘除对腰椎活动度及椎间盘应力分布的影响。 方法：采集1例L_4-5节段腰椎管狭窄症患者的CT 平扫数据,导入 Mimics 20.0软件中,建立退变腰椎L_4-5节段腰椎管狭窄有限元模型M。将模型M导入3-matic中进行手术模拟,分别为单侧小关节1/2切除及椎间盘1/4切除模型M1、双侧关节突1/2及椎间盘1/2切除模型M2、单侧关节突切除及椎间盘1/4切除模型M3。在ANSYS软件中对4种模型进行同等纯力偶矩的前屈、后伸、左侧弯、右侧弯、左旋转、右旋转6种工况活动及椎间盘同等载荷的力学对比分析。结果与结论：①与脊柱M模型比较,M1模型在6种工况下活动度相近,但M2和M3的活动度较M模型明显增大,特别是在左、右侧屈和前屈、后伸工况下,为 M模型整体活动度的130%-200%;②在椎间盘应力方面,M1模型在椎间盘后区、中区、右区各工况下等效应力的上升趋势不明显,在椎间盘左区、前区的等效应力有所增加,最大增加 63%,但没有出现较大的应力集中情况;而M2和M3模型,各区域椎间盘等效应力均出现较大程度上升趋势;③提示全内镜视下微创手术对不同类型腰椎管狭窄症减压手术精准可控,关节突关节切除及髓核摘除1/2以内对相应节段的生物力学稳定性影响较小,证实腰椎板开窗有限元模拟建模成功可靠,可为后续腰椎手术生物力学研究提供重要方法和依据。 ORCID: 0000-0002-9345-0515(刘金玉) 中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程     

The effect of thick fibers and large pores of electrospun poly(ε-caprolactone) vascular grafts on macrophage polarization and arterial regeneration

The vascular grafts prepared by electrospinning often have relatively small pores, which limit cell infiltration into the grafts and hinder the regeneration and remodeling of the grafts into neoarteries. To overcome this problem, macroporous electrospun polycaprolactone (PCL) scaffolds with thicker fibers (5–6 μm) and larger pores (∼30 μm) were fabricated in the present study. In vitro cell culture indicated that macrophages cultured on thicker-fiber scaffolds tended to polarize into the immunomodulatory and tissue remodeling (M2) phenotype, while those cultured on thinner-fiber scaffolds expressed proinflammatory (M1) phenotype. In vivo implantation by replacing rat abdominal aorta was performed and followed up for 7, 14, 28 and 100 d. The results demonstrated that the macroporous grafts markedly enhanced cell infiltration and extracellular matrix (ECM) secretion. All grafts showed satisfactory patency for up to 100 days. At day 100, the endothelium coverage was complete, and the regenerated smooth muscle layer was correctly organized with abundant ECM similar to those in the native arteries. More importantly, the regenerated arteries demonstrated contractile response to adrenaline and acetylcholine-induced relaxation. Analysis of the cellularization process revealed that the thicker-fiber scaffolds induced a large number of M2 macrophages to infiltrate into the graft wall. These macrophages further promoted cellular infiltration and vascularization. In conclusion, the present study confirmed that the scaffold structure can regulate macrophage phenotype. Our thicker-fiber electrospun PCL vascular grafts could enhance the vascular regeneration and remodeling process by mediating macrophage polarization into M2 phenotype, suggesting that our constructs may be a promising cell-free vascular graft candidate and are worthy for further in vivo evaluation.