A Poly(γ, l-glutamic acid)-citric acid based nanoconjugate for cisplatin delivery

A novel hand-held hybrid optical-gamma camera (HGC) has previously been described that is capable of displaying co-aligned images from both modalities in a single imaging system. Here, a dedicated NIR imaging system for NIR fluorescence surgical guidance has been developed for combination with the HGC . This work has evaluated the performance of two NIR fluorescence imaging systems using phantom studies, various fluorophores and various experimental configurations. The threshold detectable concentration of ICG and 800CW dyes were investigated for both systems. Bespoke lymph node phantoms simulating metastases and tissue-like layers were constructed to evaluate the detection capability. ICG could be detected at a minimum concentration of 1 μM for each camera. The lower thresholds for 800CW were 10−2 and 10−3 μM for the modified and NIR cameras, respectively. Both cameras were unable to detect small-sized targets within a 3 mm depth, but were able to identify larger targets as deep as 7 mm. Further improvements are required to optimise the NIR-fluorescence systems for subsequent combination with the HGC to undertake dual gamma-NIR fluorescence intraoperative imaging.

Intraoperative identification of the cancer location is often difficult during robot-assisted surgery, especially in early stage cancers. This study aimed to investigate the feasibility and accuracy of a novel endoscopic clip emitting near-infrared (NIR) fluorescence during robot-assisted surgery for gastrointestinal cancer. Preoperative placement of endoscopic marking clips equipped with NIR fluorescent resin was performed to determine the resection margins in six patients with gastrointestinal cancer. During robot-assisted surgery, a NIR fluorescence imaging system was used to detect the fluorescence. The evaluation examined whether fluorescence from the clips was visualized during robot-assisted surgery. The NIR fluorescent signals emitted from the clips were successfully detected in all six patients from the serosal surfaces, resulting in the quick and accurate identification of the resection line. There were no significant differences in age, sex, or body mass index between the patients in whom we could detect NIR fluorescence. This novel NIR fluorescent clip is a promising diagnostic tool for accurately detecting tumor locations during robot-assisted surgery for gastrointestinal cancer.

Rapamycin loaded magnetic Fe3O4/carboxymethylchitosan nanoparticles as tumor-targeted drug delivery system: Synthesis and in vitro characterization

Therapeutic target for over-expressed αvβ3 integrins in angiogenic endothelial cells and tumors is one of the promising approaches for cancer imaging and therapy. In the previous study, we demonstrated that heparin–lithocholic acid functionalized with cyclic RGDyK (cRGD–HL) had potent angiogenesis inhibition and tumor regression effects. The aim of this study is to validate the targeting property and specificity of cRGD–HL to αvβ3 integrin-expressing endothelial cells and tumor tissues by Cy5.5-labeled cRGDyK (RGD-Cy5.5) as αvβ3 integrin imaging agent and near-infrared fluorescence (NIRF) imaging systems. In this study, we demonstrated that cRGD–HL markedly inhibited the binding of fluorescein-labeled αvβ3 antibody to αvβ3 integrin-expressing endothelial cells when compared to non-functionalized heparin derivatives. Furthermore, in vivo NIRF images showed that cRGD–HL could decrease the NIRF signal intensities in both αvβ3 integrin-positive tumor (U87 MG) and αvβ3 integrin-negative tumor (SCC7) more effectively than non-functionalized heparin derivatives could. Therefore, with the help of αvβ3 integrin imaging agent and NIRF imaging systems, we verified that the functionalized cRGD–HL has much stronger tumor targeting property and specificity against αvβ3 integrin-expressing endothelial cells and tumors than non-functionalized heparin derivatives. Also, we believe that cRGD–HL will be useful and give affirmative outcomes for the treatment of angiogenesis-related diseases.

Adoptive cellular immunotherapy (ACI) has been demonstrated to be a promising cancer therapeutic, however, the distribution of immune cells injected into a tumor-bearing body is unclear. In this study, we investigated the tumor-targeting capacity of cytokine-induced killer (CIK) cells and cytotoxic T lymphocytes (CTLs) in a human gastric carcinoma orthotopic mouse model using a near-infrared fluorescence imaging system. CIK cells and tumor-specific CTLs were prepared with the near-infrared fluorescent dye DiR. As expected, no significant change in the proliferation rate or antitumor activity of CIK cells and CTLs was noted after labeling with DiR. Furthermore, a gastric carcinoma orthotopic model was established using a fibrinogen-thrombin method in nude mice followed by intraperitoneal infusion of the labeled immune cells into nude mice with established gastric carcinoma. Dynamic tracing of the immune cells was performed using a fluorescence-based live imaging system. Concentrated fluorescence signals were observed for a minimum of two weeks at the tumor site in mice infused with either CIK cells or CTLs with a peak signal at 48 h. Notably, CTLs were more persistent at the tumor site and exhibited a more intense antitumor activity than CIK cells following infusion. These results provided visual evidence of the tumor-targeting capacity of immune cells in live animals.

The utilization of metal-organic frameworks in tumor-targeted drug delivery systems

Photodynamic therapy (PDT) is an effective therapy for tumor, which involves the administration of photosensitizers followed by illumination. However, the insolubility and non-targeting are defects of photosensitizers. For targeting the acid environment at tumor site, Poly(ethylene glycol) methacrylate-co-2-(Diisopropylamino) ethyl methacrylate (PEGMA-co-DPA) copolymers were synthesized in the presence of 2,2’-Azobis-isobutyronitrile (AIBN) and then formed pH sensitive nanoparticles to encapsulate a photosensitizer, m-THPC. The characteristic of these copolymers were evaluated by 1H nuclear magnetic resonance and gel permeation chromatography. The pH effect on aggregation/deaggregation and critical aggregation concentration (CAC) of the nanoparticles was studied by using pyrene as a probe. The results showed that the critical aggregation pH (Ph*) of the polymers were from 5.8 to 6.6 and the CAC were from 0.0045 to 0.0089 wt% at pH 7.4. The m-THPC loaded nanoparticles were prepared by oil-in-water. The size and morphology of nanoparticles were observed using dynamic light scattering and transmission electron microscopy. The results indicated that the nanoparticles were sphere and the size was 132 nm. The drug encapsulation efficiency was 89%. The in vitro release profile performed that the release rate of m-THPC at pH 5.0 (58% m-THPC released within 48 hours) was faster than at pH 7.0 (10% m-THPC released within 48 hours). The in vitro PDT efficiency was tested with HT-29 cell line by MTT assay. These findings suggest that the pH sensitive nanoparticles prepared in this study are potential carriers for tumor targeting.

To assess the merits of PEGylated poly (lactic-co-glycolic acid) (PEG-PLGA) nanoparticles as drug carriers for tumor necrosis factor-α receptor blocking peptide (TNFR-BP), PEG-PLGA copolymer, which could be used to prepare the stealth nanoparticles, was synthesized with methoxypolyethyleneglycol, DL-lactide and glycolide. The structure of PEG-PLGA was confirmed with 1H-NMR and FT-IR spectroscopy, and the molecular weight (MW) was determined by gel permeation chromatography. Fluorescent FITC-TNFRBP was chosen as model protein and encapsulated within PEG-PLGA nanoparticles using the double emulsion method. Atomic force microscopy and photon correlation spectroscopy were employed to characterize the stealth nanoparticles fabricated for morphology, size with polydispersity index and zeta potential. Encapsulation efficiency (EE) and the release of FITC-TNFR-BP in nanoparticles in vitro were measured by the fluorescence measurement. The stealth nanoparticles were found to have the mean diameter less than 270 nm and zeta potential less than −20 mV. In all nanoparticle formulations, more than 45% of EE were obtained. FITC-TNFRBP release from the PEG-PLGA nanoparticles exhibited a biphasic pattern, initial burst release and consequently sustained release. The experimental results show that PEG-PLGA nanoparticles possess the potential to develop as drug carriers for controlled release applications of TNFR-BP.

Amphiphilic block copolymers composed of D,L-lactide, trimethylene carbonate and the methoxy poly (ethylene glycol) (PETLA) were synthesized with ringopening copolymerization. Studies on the micellization and drug-controlled release behavior of PETLA were performed. Both of the copolymers and the micelles were characterized with the methods of 1H nuclear magnetic resonance (1H-NMR), fluorescence spectroscopy, gel permeation chromatographic (GPC), dynamic light scattering (DLS), transmission electron microscopy (TEM) and ultraviolet-visible spectroscopy (UV). As a result, the critical micelle concentration of the copolymer was decreased with the increase of the hydrophobic chain length. DLS results indicated the diameters of the micelle were increased with increasing hydrophobic length. TEM photographs illustrated that micelles MT1 were regularly spherical with the diameter from 30 nm to 40 nm. Taking 9-nitro-20(S)-camptothecin (9-NC) for the model drug, the release profiles in vitro show that the release behavior from micelles was controllable and nearly in zero order after the initial burst release.

The determination of the physicochemical properties of polyelectrolytes in water solution has fundamental importance for the description of their possible application. Gel permeation chromatography (GPC), dynamic light scattering (DLS) and viscosimetry studies of the polyelectrolytes were performed for this goal. The polyelectrolytes were obtained from polystyrene waste. Waste polystyrene foam (EPS) as reference material was converted into polymeric flocculants (NaEPSS) in chemical reactions.1–3 Products with determined molecular weight and number of sulphonic group per monomer unit were divided into several fractions by fractional precipitation with 0.5 M aqueous NaOH as the solvent and 2-propanol as the precipitant. Viscosity measurements of water solutions of obtained polyelectrolytes NaEPSS were performed and the results were used for the calculation of the viscosity average molecular weights. The obtained results were then compared with the data from GPC (gel permeation chromatography) measurements and DLS (dynamic light scattering) results. It was stated that the changes of the molecular weights for the fractions of the NaEPSS values may be the result of side reactions occurring during the sulphonation process and of the irregular course of the fractionation process.

Theranostic polymeric nanomaterials are of special important in cancer treatment. Here, novel galactose targeted pH-responsive amphiphilic multiblock copolymer conjugated with both drug and near-infrared fluorescence (NIR) probe has been designed and prepared by a four-steps process: (1) ring-opening polymerization (ROP) of N-carboxy anhydride (NCA) monomers using propargylamine as initiator; (2) reversible addition-fragmentation chain transfer (RAFT) polymerization of oligo(ethylene glycol) methacrylate (OEGMA) and gal monomer by an azido modified RAFT agent; (3) combing the obtained two polymeric segments by click reaction; (4) NIR copolymer prodrug was synthesized by chemical linkage of both cyanine dye and anticancer drug doxorubicin to the block copolymer via amide bond and hydrazone, respectively. The obtained NIRF copolymers were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and its was measured by means of micelles dynamic light scattering (DLS), field emission transmission electron microscopy (FETEM), and UV-vis and fluorescence spectrophotometry. The prodrug has strong fluorescence in the near-infrared region, and a pH sensitive drug release was confirmed at pH of 5.4 via an in vitro drug release experiment. Confocal laser scanning microscopy (CLSM) and flow cytometry experiments of the prodrug on both HepG2 and NIH3T3 cells reveal that the galactose targeted polymeric prodrug shows a fast and enhanced endocytosis due to the specific interaction for HepG2 cells, indicating the as-prepared polymer is a candidate for theranosis of liver cancer.

Extremely long tumor retention, multi-responsive boronate crosslinked micelles with superior therapeutic efficacy for ovarian cancer

The potential for blood vessel engineering of PHSRN-modified polymer: HUVEC cell affinity evaluation and integrin-mediated mechanism study

Open AccessCCS ChemistryRESEARCH ARTICLE27 May 2022Controllable Polymerization of N-Substituted β-Alanine N-Thiocarboxyanhydrides for Convenient Synthesis of Functional Poly(β-peptoid)s Ximian Xiao†, Min Zhou†, Zihao Cong, Longqiang Liu, Jingcheng Zou, Zhemin Ji, Ruxin Cui, Yueming Wu, Haodong Zhang, Sheng Chen, Maoquan Li and Runhui Liu Ximian Xiao† State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237 , Min Zhou† State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237 , Zihao Cong Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Research Center for Biomedical Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 , Longqiang Liu Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Research Center for Biomedical Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 , Jingcheng Zou Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Research Center for Biomedical Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 , Zhemin Ji Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Research Center for Biomedical Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 , Ruxin Cui Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Research Center for Biomedical Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 , Yueming Wu Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Research Center for Biomedical Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 , Haodong Zhang Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Research Center for Biomedical Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 , Sheng Chen Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Research Center for Biomedical Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 , Maoquan Li Department of Interventional and Vascular Surgery, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai 200072 and Runhui Liu *Corresponding author: E-mail Address: [email protected] State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237 Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Research Center for Biomedical Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 https://doi.org/10.31635/ccschem.022.202201840 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Poly(β-peptoid) is a class of polypeptide mimics that possesses excellent biocompatibility and resistance to proteolysis. However, the synthesis of poly(β-peptoid)s with functionalities is a long-standing challenge that greatly hinders the functional study and application of poly(β-peptoid)s. We report a controllable and easy synthesis of poly(β-peptoid)s bearing diverse functionalities via the ring-opening polymerization on N-substituted β-alanine N-thiocarboxyanhydrides (β-NNTAs). The polymerization can be carried out in open vessels under mild conditions using amines as the initiators to provide poly(β-peptoid)s with targeted molecular weights, narrow dispersities, and diverse functionalities in the side chains and termini. The β-NNTAs polymerization is even compatible with initiators bearing unprotected hydroxyl groups. The amphiphilic/cationic poly(β-peptoid)s exhibit a broad spectrum and potent antibacterial activities against multidrug-resistant bacteria. In addition, the highly favored stability of β-NNTA monomers for purification and storage highlights the advantages of this β-NNTA polymerization strategy for poly(β-peptoid)s synthesis, functional study, and application as a synthetic mimic of polypeptides. Download figure Download PowerPoint Introduction Poly(β-peptoid)s, as a class of polypeptide mimics, have a polyamide backbone similar to polypeptides but with an extra methylene group and with the proton of nitrogen–hydrogen bond in the backbone substituted by an alkyl group.1–4 Poly(β-peptoid)s have superior biocompatibility and excellent stability against proteolysis and therefore demonstrate promising biological applications in biomimetic scaffolds,3 antifouling properties,5 and antibacterials.6 However, the lack of an effective synthetic strategy is the long-standing challenge that greatly hinders the advance of this field and the application of poly(β-peptoid)s. Conventional solid-phase synthesis is applied to prepare poly(β-peptoid)s using either direct amide bond formation or via aza-Michael addition.7,8 However, no poly(β-peptoid)s with over 10 residues can be obtained using the solid-phase synthesis due to the low efficiency of this chemistry. Compared with the preparation of polypeptides and poly(α-peptoid)s, it is hard to obtain structurally diverse and functional poly(β-peptoid)s. Current solid-phase synthesis of poly(β-peptoid)s is also time-consuming, expensive, and difficult in scale up.9 To overcome the shortcomings of solid-phase synthesis in preparing poly(β-peptoid)s, polymerization strategies have been explored. Jia et al. reported a successful synthesis of poly(β-peptoid)s from the copolymerization of N-alkylaziridines and carbon monoxide using cobalt catalysts (Figure 1a).1,10 Nevertheless, this polymerization relies on high-pressure reaction conditions and a metal catalyst. Since 1954, to realize a mild synthesis of poly(β-peptoid)s, amine-initiated polymerization on N-substituted β-alanine N-carboxyanhydrides (β-NNCAs) has been explored (Figure 1b).2,11,12 However, this strategy suffers from the instability of β-NNCA monomers.12 In addition, the above two polymerization strategies for poly(β-peptoid)s synthesis are both highly sensitive to moisture and have structural diversity limited to N-alkyl and/or N-aryl substitution, which has been a serious obstacle to the synthesis, functional study, and application of poly(β-peptoid)s. Therefore, we need to develop a convenient, mild, and open vessel synthesis of poly(β-peptoid)s. Meanwhile, it is also vital to explore structurally diverse poly(β-peptoid)s for their functions and applications. Figure 1 | Polymerization strategy for the synthesis of poly(β-peptoid)s. Download figure Download PowerPoint Herein, we report the synthesis of poly(β-peptoid)s from a controllable ring-opening polymerization on N-substituted β-alanine N-thiocarboxyanhydrides (β-NNTAs) (Figure 1c). This controllable and living polymerization on β-NNTAs can be achieved using variable amines as the initiator to obtain poly(β-peptoid)s with predictable molecular weight (Mn) controllable degree of polymerization (DP) and low dispersity (Đ) without using any catalyst. This polymerization can be operated conveniently in an open vessel. Moreover, β-NNTA monomers can be easily obtained with a variety of N-substitutions, which enables a breakthrough in the structural diversity of resulting poly(β-peptoid)s. In addition, a variety of terminal functional groups can be introduced into poly(β-peptoid)s via the amine initiators. This strategy for poly(β-peptoid)s synthesis from controllable and living polymerization on β-NNTAs addresses the long-lasting challenges in this field and provides a convenient alternative to facilitate the synthesis, functional study, and application of poly(β-peptoid)s. Experimental Methods All reagents and solvents were purchased from Adamas Chemical Reagent Co., Ltd. (Shanghai, China) and used as received unless otherwise specified. Petroleum ether (PE), ethyl acetate (EtOAc), N,N-dimethylformamide (DMF), tetrahydrofuran (THF), toluene (Tol), acetonitrile (MeCN), dioxane, dimethyl sulfoxide (DMSO), and 1-methyl-2-pyrrolidinone (NMP) were purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd. and used as received without purification. Synthesized intermediates were purified using a SepaBean machine equipped with Sepaflash columns produced by Santai Technologies (Changzhou, China) Co. Ltd. Nuclear magnetic resonance (NMR) spectra were collected on a Bruker spectrometer at 400 MHz or 600 MHz, using CDCl3 or CF3COOD as solvents. Chemical shifts are referenced to residual protons in the deuterated NMR solvents. High-resolution electrospray ionization time-of-flight mass spectrometry (HRESI-TOF-MS) was collected on a Waters Xevo G2 TOF mass spectrometer (Waters Technologies Shanghai Ltd) and high-resolution electron ionization time-of-flight mass spectrometry (HREI-TOF-MS) was collected on a Waters GCT. High-performance liquid chromatography (HPLC) analysis was carried out on a Shimadzu LC-20AR HPLC System (Shimadzu (Shanghai) Global Laboratory Consumables Co., Ltd.) equipped with a Gemini 5 μm NX-C18 column. Gel permeation chromatography (GPC) was performed on a Waters GPC instrument equipped with a Brookhaven BI-MwA multiangle light-scattering detector (BI-MwA, Brookhaven Instruments Shanghai Representative Office) and a refractive index detector (Waters 2414) using DMF, supplemented with 0.01 M LiBr, as the mobile phase at a flow rate of 1 mL/min at 50 °C. The GPC were equipped by a Tosoh TSKgel Alpha-2500 column (particle size 7 μm), a Tosoh TSKgel Alpha-3000 column (particle size 7 μm), and a Tosoh TSKgel Alpha-4000 column (particle size 10 μm, 300 × 7.8 mm) linked in series. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) experiments were conducted on an AB Sciex 4800 Plus MALDI TOF/TOF analyzer (Shanghai AB Sciex Analytical Instrument Trading Co., Ltd.) using a 355 nm laser, a Shimadzu MALDI-7090TM TOF-TOF mass spectrometer (Shimadzu (Shanghai) Global Laboratory Consumables Co., Ltd.) with 2,5-dihydroxybenzoic acid (DHB) as the matrix. Dynamic light scattering (DLS) measurements were used to measure hydrodynamic diameters of assembled polymers using a Zetasizer Nano-ZS instrument, Model ZEN3600 (Malvern Instruments Ltd., Malvern, United Kingdom). Transmission electron microscopy (TEM) measurements were conducted using a JEOL JEM-1400 TEM (JEOL (Beijing) Co., Ltd. Shanghai Branch) at an acceleration voltage of 100 kV. Time-lapse fluorescent confocal imaging was performed using a Leica TCS SP8 system (Leica Microsystems) equipped with LAS X v3.5.2. software (Leica Microsystems) for acquisition control. Fluorescence spectra of the samples were performed on a Varian Cary Eclipse fluorescence spectrophotometer (Varian China Ltd., Shanghai Office). Results and Discussion Using pFBn β-NNTA ( 1a) as a model, we conducted the ring-opening polymerization on β-NNTA using 4-tert-butylbenzylamine (tBuBnNH2) as the initiator in variable solvents including DMF, THF, Tol, dioxane, MeCN, DMSO, and NMP ( Supporting Information Scheme S13, Figure S1, Table S1). Poly(N-pFBn-β-ala) was successfully obtained in polymerization using most common solvents as a single peak of GPC trace with narrow dispersity (Đ = 1.04–1.11), except that a bimodal peak of GPC trace was observed for polymerization using DMSO and NMP as the solvent. Among all solvents that are compatible with β-NNTA polymerization, DMF afforded the resulting poly(β-peptoid) with a polymer length (obtained DP = 21) almost identical to the expectation (calculated DP = 20). Considering that DMF normally provides excellent solubility and is a widely used solvent for polypeptide and polypeptoid synthesis, we chose DMF as the solvent for continuous β-NNTA polymerization studies. To examine if the polymer length of amine-initiated β-NNTA polymerization is controllable, we tried the polymerization on pFBn β-NNTA ( 1a) in DMF using variable [M]0/[I]0 ratios. The results showed that poly(β-peptoid)s were obtained with an incrementally increased chain length from 22 mer (Mn = 4.1 kDa) to 150 mer (Mn = 27.1 kDa) with narrow dispersities (Đ = 1.18–1.20) and DP almost identical to the prediction (Table 1, entries 1–5, Figure 2a). These results demonstrate the excellent controllability of the β-NNTA polymerization. Kinetics study showed that the polymerization had an evolution of Mn that showed in linear correlation with monomer conversion and kept narrow dispersity (Đ = 1.09–1.18) throughout the whole process (Figure 2b). It is worth mentioning that the polymerization showed first-order kinetic characteristics (kp[I] = 0.018 h−1) and over 90% conversion of β-NNTA monomer within 14 h (Figure 2c). The polymerization on pFBn β-NNTA in DMF was completed within 20 h. Table 1 | Poly(β-peptoid)s Synthesized from β-NNTAs Polymerizationa Entry M M0/I Mn, th (kDa) Mn (kDa)b DPb Ðb 1 1a 20 3.7 4.1 22 1.19 2 1a 40 7.3 7.3 40 1.20 3 1a 80 14.6 14.6 80 1.19 4 1a 100 18.1 17.9 99 1.18 5 1a 150 27.0 27.1 150 1.20 6 1b 20 3.4 3.2c 19c 1.12d 7 1c 20 4.3 4.6 21 1.13 8 1d 40 7.4 7.2 39 1.18 9 1e 20 2.4 2.1c 17c 1.15d 10 1f 20 2.7 2.4 18 1.17 11 1g 20 2.7 3.6c 27c 1.08d 12 1h 20 4.8 3.3 14 1.09 13 1i 20 5.1 4.0 16 1.13 14 1a-r- 1d 40/40 14.6 13.9 76 1.17 15 1a1st 20 3.7 3.7 20 1.16 1d2nd 20 7.4 7.3 40 1.15 aAll polymerizations were conducted using tBuBnNH2 as initiator in a sealed vessel at 60 °C. [M]0 at 2 M for entry 5, [M]0 at 1 M for other entries. bMn, DP, and Đ were determined by GPC using DMF as the mobile phase at a flow rate of 1 mL/min. cMn and DP were determined by NMR. dĐ was determined by MALDI-TOF-MS. Mn,th is the theoretical number average molecular weight; Mn,obtained is the obtained number average molecular weight; DP is the obtained degree of polymerization; Đ means the dispersity. Figure 2 | (a) Plots of Mn and Đ as a function of the [M]0/[I]0 ratio for pFBn β-NNTA. Inset: Overlay of GPC profiles at different [M]0/[I]0 ratios corresponding to entries 1–5 in Table 1. (b) Profiles of Mn and Đ as a function of pFBn β-NNTA conversions at the [M]0/[I]0 ratio of 20/1. Inset: Overlay of GPC profiles at different monomer conversions. (c) Kinetic profiles of conversion and ln([M]0/[M]) vs time at the [M]0/[I]0 ratio for pFBn β-NNTA of 20/1 using tBuBnNH2 as the initiator. (d) GPC traces of the block copolymer corresponding to entry 15 in Table 1. (e) The ring-closure synthesis for β-NNTAs. Reaction condition: 1.0 equiv. PBr3, anhydrous CH2Cl2, 0 °C to r.t., 4 h. (f) The purification of Bu β-NNTA via silica gel chromatography (9:1 PE:EtOAc). (g) Stability analysis of β-NNTA and β-NNCA at r.t. (h) Open-vessel polymerization of ThEt β-NNTA at 2 g scale at 60 °C in DMF, [M]0 = 1 M. Mn, DP and Đ were determined by GPC. Download figure Download PowerPoint The side-chain functionality or structural diversity of peptide mimics plays an essential role in defining their activity, function, and application.13–17 However, for poly(β-peptoid)s, current synthetic strategies using either the copolymerization of N-alkylaziridines and carbon monoxide or the ring opening polymerization of β-NNCAs can only afford poly(β-peptoid)s with N-alkyl or N-aryl functional groups.1,2 This challenge encouraged us to explore the synthesis of functional poly(β-peptoid)s from the polymerization on β-NNTAs. Structurally diversified β-NNTAs were easily synthesized from primary amines (Figure 1c, β-NNTA 1a– 1i, Supporting Information Schemes S1–S10 and Figures S32–S57). In addition, tBuBnNH2 successfully initiated the polymerization of all those β-NNTAs in our study to afford corresponding poly(β-peptoid)s in narrow dispersities (Đ = 1.09–1.18) and with diversified structures or side-chain functional groups including aromatic groups (4-fluorobenzyl in pFBn β-NNTA, benzyl in Bn β-NNTA, (4-chlorophenyl)ethyl in pCPE β-NNTA), heterocycles in ThEt β-NNTA, alkyl groups (cyclopropyl in cPr β-NNTA, isobutyl in iBu β-NNTA, and n-butyl in Bu β-NNTA), carboxylates in Cbz-Et β-NNTA, and amines in Cbz-AE β-NNTA (Table 1, entries 1–13, Figure 2a, and Supporting Information Figures S2–S9). The β-NNTA polymerization was also feasible for copolymerization. A random copolymerization on the mixture of pFBn β-NNTA and ThEt β-NNTA afforded poly[(N-pFBn-β-ala)-r-(N-ThEt-β-ala)] with the expected polymer length (DP = 76) and a narrow dispersity (Đ = 1.17) (Table 1, entry 14, Supporting Information Scheme S14 and Figure S10). Sequential addition of pFBn β-NNTA and ThEt β-NNTA in one-pot synthesis gave the first block of poly(N-pFBn-β-ala) at 20 mer with a narrow dispersity (Đ = 1.16) and the expected final block copolymer poly(N-pFBn-β-ala)-b-poly(N-ThEt-β-ala) at 40 mer with a low dispersity (Đ = 1.15) (Table 1, entry 15, Figure 2d, and Supporting Information Scheme S15). All these results demonstrate that the amine-initiated β-NNTA polymerization has excellent controllability to prepare poly(β-peptoid)s with diversified structures and side-chain functionalities. The stability of β-NNTA is vital to its purification and storage, ultimately contributing to structural and functional diversity of poly(β-peptoid)s. We found that β-NNTA displayed stability superior to β-NNCA with the same side chain. It is worth mentioning that we can obtain all β-NNTAs with high yield (81−93%) during the ring-closing process via silica gel chromatography (Figure 2e). Purification of β-NNTA via silica gel chromatography makes it possible to easily obtain pure oily β-NNTA monomers (representative Bu β-NNTA in Figure 2f), whereas β-NNCA is less stable and will decompose on silica gel, making the purification of oily β-NNCA monomers a headache ( Supporting Information Scheme S11 and Figures S58–S60). In addition, during storage, the purity of β-NNTA such as pFBn β-NNTA was maintained above 99% over 27 days at room temperature and showed no significant decomposition even after half a year at −20 °C (Figure 2g, Supporting Information Figure S11), whereas the purity of the corresponding β-NNCA sharply decreased to 23% after 27 days (Figure 2g). The open-vessel polymerizations have been reported in the synthesis of polypeptides and polypeptoids.18–27 The excellent stability of β-NNTA encouraged us to explore its polymerization in an open flask outside of a glove box. A gram-scale β-NNTA polymerization was achieved successfully in an open flask to give the resulting poly(N-ThEt-β-ala)20 in 90.1% yield (Figure 2h). The living and controllable polymerization of β-NNTAs encouraged us to explore the reaction mechanism. We proposed that the polymerization is initiated by nucleophilic addition of primary amine at the C1 carbonyl in a β-NNTA ring, followed by the ring opening of β-NNTA and release of the small molecule carbonyl sulfide (COS) to give an intermediate 1 that has an N-terminal secondary amine as the reactive center to attack another β-NNTA for chain propagation (Figure 3a).24,26,28,29 To provide mechanistic insights into chain initiation and propagation, Fourier transform infrared (FT-IR) characterization on a 1∶1 molar ratio mixture of tBuBnNH2 and pFBn β-NNTA was conducted (Figure 3b). Compared with pFBn β-NNTA, an above 1∶1 mixture had a shifted signal of the C1 carbonyl group from 1715.9 to 1642.1 cm−1 (C1′ in the mixture). The disappearance of C2 carbonyl signal at 1648.8 cm−1 indicated the ring opening of β-NNTA and subsequent release of COS. In addition, proton NMR characterization of an immediately prepared mixture of pFBn β-NNTA and tBuBnNH2 solution in CDCl3 at variable ratios showed a reduction of Ha and Hb peaks in the β-NNTA ring and the emergence of upfield-shifted Ha′ and Hb′ peaks in the β-NNTA ring opening product simultaneously, which indicated a quick nucleophilic addition of tBuBnNH2 to the C1 carbonyl in the β-NNTA ring at the initiation step (Figure 3c). Figure 3 | (a) Proposed mechanism of primary amine-initiated β-NNTA polymerization. (b) FT-IR spectra of β-NNTA, tBuBnNH2 and a 1∶1 β-NNTA/tBuBnNH2 mixture (DMF, room temperature, [M]0=0.5 M). (c) Instantaneous 1H NMR titration spectra on a mixture of β-NNTA/tBuBnNH2 in variable ratio (CDCl3, 25°C. [M]0=0.2 M). (d) HRESI-TOF-MS analysis on the 1∶1 β-NNTA/tBuBnNH2 mixture (DMF, room temperature, [M]0=0.5 M). (e) MALDI-TOF-MS of poly(N-pFBn-β-ala)20 (entry 1 in Table 1) with the corresponding chemical structures. Download figure Download PowerPoint HRESI-TOF-MS characterization on the above 1∶1 mixture showed a clear spectrum and high intensity fragment at m/z 343.2187 for intermediate 1 (Figure 3d), consistent with the result in the above NMR analysis and confirming nucleophilic addition of tBuBnNH2 to the β-NNTA ring during initiation. This was further confirmed by examining the final poly(β-peptoid)s (poly(N-pFBn-β-ala)20) using MALDI-TOF-MS characterization. The 179 Da difference between peaks reflected successful incorporation of the β-peptoid residues. Specific mass corresponding to each peak revealed the incorporation of a C-terminal tBuBnNH group via nucleophilic addition during initiation (Figures 3a and 3e). These results echoed the controllable β-NNTA polymerization and living polymerization with a normal amine mechanism. The terminal functionalization is important for the structural diversity and function of peptide mimics, for instance, in bioactive molecule conjugation and fluorescence labelling.30–39 The aforementioned open-vessel polymerization encouraged us to further explore C-terminal functionalization in an open vessel ( Supporting Information Scheme S16). Using primary amines as the initiator for the ring-opening polymerization on β-NNTAs allows the easy incorporation of diverse functionalities into the C-terminal of poly(β-peptoid) chains including alkenyl, alkynyl, adamantane, bromophenyl, azide, protected thiol, protected amine, methoxy, polyethylene glycol (Figure 4a, 2a− 2j), unprotected base, unprotected hydroxyl groups, aggregation-induced emission luminogen (AIEgen), and aggregation-caused quenching (ACQ) fluorophore (Figures 4b and 4c, 2k− 2q). In addition to terminal all poly(β-peptoid)s were successfully synthesized with excellent of chain length and narrow dispersities (Đ = ( Supporting Information Figures Figure 4 | amine-initiated β-NNTA polymerization in an open vessel. (a) functional primary amines as C-terminal groups. (b) Representative primary amines with nucleophilic groups. (c) Functional of C-terminal poly(β-peptoid)s. Download figure Download PowerPoint is the polymerization on β-NNTAs can be initiated by primary amines that have an unprotected and hydroxyl group (Figure The of unprotected reactive groups of β-NNTA polymerization the synthesis of poly(β-peptoid)s with function groups without and This encouraged us to explore a β-NNTA polymerization using unprotected as the initiator. the polymerization also hydroxyl groups to give the expected poly(β-peptoid)s with a narrow dispersity (Đ = GPC and a terminal in the polymer chain as by (Figure 4c, Supporting Information Figure The poly(β-peptoid)s in the solvent of the application of this polymerization in (Figure 4c, This mild β-NNTA polymerization also us to poly(β-peptoid)s with terminal fluorescence groups such as the ( ( Supporting Information Scheme and Figures and and the fluorophore ( with the expected polymer length and low dispersity (Figure 4c, and 2q). and displayed and showed the intensity at 90% and which a application of this β-NNTA polymerization and resulting poly(β-peptoid)s for Poly(β-peptoid)s have backbone structures similar to and excellent stability against which the possible of poly(β-peptoid)s as a synthetic mimic of polypeptides for a variety of applications. However, current functional study and application of poly(β-peptoid)s are limited due to the obstacle of poly(β-peptoid) To the of our no antibacterial application of poly(β-peptoid)s has been due to the to poly(β-peptoid)s via The mild and controllable synthesis of poly(β-peptoid)s from β-NNTA polymerization enables us to prepare structurally diverse poly(β-peptoid)s for functional including Using Cbz-AE β-NNTA and pFBn β-NNTA as for we synthesized poly(β-peptoid)s that were of both the and the (4-fluorobenzyl with an incrementally increased ratio of the as synthetic mimics of (Figures and These poly(β-peptoid)s were obtained at 20 mer at low dispersities (Đ = (Figures and GPC traces in Supporting Information Figure Figure 5 | Open-vessel polymerization for synthesis of poly(β-peptoid)s for antibacterial studies. (a) A of poly(β-peptoid)s. (b) of poly(β-peptoid)s. (c) The of the poly(β-peptoid)s against 5 of bacteria. (d) GPC characterization of side-chain protected from different (e) The of obtained from different against (f) Time-lapse confocal fluorescence imaging on the between and in the of is 1 Download figure Download PowerPoint The obtained poly(β-peptoid)s were for their against including multidrug-resistant

Fundamental studies on the separation of coal derivatives by means of gel permeation chromatography (GPC) are reported on (1) the chromatographic conditions for preparative GPC separation for structural analyses of coal and (2) basic experiments to odtain the molecular weight distributtion from analytical GPC elution curves using the chloroform soluble qart (γ-part) of pyridine extract from Akabira coal. On the basis of this informaton, the distributions of molecularweight of oil and asphaltene obtained from hydrogenolysis of Akabira coal are investigated by GPC analyses and their variation with reaction temperature is discussed.The petroleum soluble portion (γ1-part) and the insoluble portion (γ2-4-part) from the γ-part were selected as the sample for the discussion of the optimum conditions for GPC separation, such as pore size of gel and elution solvent. From the experimental results, it is obvious that separation by preparative GPC is achieved, odtaining fractions of considerably narrow molecular weight distribution. This contributed remarkably to the resolution of thechemical structure of coal. The relationship detween the elution volume (Ve) of the analytical GPC and average molecular weight (M) estimated by vapor pressure osmometry is fairly good for the fractionation products from preparative GPC (Fig. 9, 10). The M-Ve correlation lines of the 1- and the 2-4-parts were straight lines of different slope. Therefore it was assumed that the difference was due to a difference in structural type on the components. Consequently, these γ relationships of log M-Ve can be applied to the estimation of the molecular weight distribution from analytical GPC chromatograms as the correlation lines of high-molecular and low-molecular weight components respectively for the coal derived liquids.Oil and asphaltene in hydrogenolysis products werealso separated into fraction on the basis of molecular weight by preparative GPC and each fraction was correlated by elution counts of analytical GPC and average molecular weight. The results of these relationships were in fairly good agreement with correlation lines of log M-Ve odtained from the γ1 and the γ2-4 componets respectively (Fig. 13, 14). From the elution curves of analytical GPC for oil and asphaltene of varying reaction temperature, it is recognized that the distribution of molecular wight for asphaltene shifts gradually in the direction of a lower molecular weight distribution as the reaction temperature increases. On the other hand, the distribution of moleclar weight of oil changes only slightly and tends to converge to the constant distribution of low molecular weight components.