Characterization and in vitro release studies of oral microbeads containing thiolated pectin–doxorubicin conjugates for colorectal cancer treatment

Novel oral microbeads were developed based on a biopolymer–drug conjugate of doxorubicin(DOX) conjugated with thiolated pectin via reducible disulfide bonds. The microbeads were fabricated by ionotropic gelation with cations such as Al3+, Ca2+ and Zn2+. The results showed that using zinc acetate can produce the strongest microbeads with spherical shape.However, the microbeads prepared from thiolated pectin–DOX conjugate were very soft and irregular in shape. To produce more spherical microbeads with suitable strength, the native pectin was then added to the formulations. The particle size of the microbeads ranged from 0.87 to 1.14 mm. The morphology of the microbeads was characterized by optical and scanning electron microscopy. DOX was still in crystalline form when used in preparing the microbeads, as confirmed by powder X-ray diffractometry. Drug release profiles showed that the microbeads containing thiolated pectin–DOX conjugate exhibited reduction-responsive character;in reducing environments, the thiolated pectin–DOX conjugate could uncouple resulting from a cleavage of the disulfide linkers and consequently release the DOX. The best-fit release kinetics of the microbeads containing thiolated pectin–DOX conjugate, in the medium without reducing agent, fit the Korsmeyer–Peppas model while those in the medium with reducing agent fit a zero-order release model. These results suggested that the microbeads containing thiolated pectin–DOX conjugate may be a promising platform for cancer-targeted delivery of DOX, exploiting the reducing environment typically found in tumors.

Controllably partial removal of thiolate ligands from unsupported Au_(25) nanoclusters by rapid thermal treatments for electrochemical CO_(2)reduction

Colloidal synthesis of metal nanoclusters will inevitably lead to the blockage of catalytically active sites by organic ligands.Here,taking[Au_(25)(PET)_(18)]-(PET=2-phenylethanethiol)nanocluster as a model catalyst,this work reports a feasible procedure to achieve the controllably partial removal of thiolate ligands from unsupported[Au_(25)(PET)_(18)]-nanoclusters with the preservation of the core structure.This procedure shortens the processing duration by rapid heating and cooling on the basis of traditional annealing treatment,avoiding the reconfiguration or agglomeration of Au_(25)nanoclusters,where the degree of dethiolation can be regulated by the control of duration.This work finds that a moderate degree of dethiolation can expose the Au active sites while maintaining the suppression of the competing hydrogen evolution reaction.Consequently,the activity and selectivity towards CO formation in electrochemical CO_(2)reduction reaction of Au_(25)nanoclusters can be promoted.This work provides a new approach for the removal of thiolate ligands from atomically precise gold nanoclusters.

Bioadhesiveness of thiolated pectin for buccal delivery of carbenoxolone sodium

Pectin is a biopolymer that has numerous useful purposes in food and beverage industry, cosmetic products and pharmaceutical fields. One of the important properties of pectin is its bioadhesive properties. Native pectin provides fair bioadhesive properties that can be improved by modification of pectin structure. The immobilization of thiol groups on polymer can significantly improve the bioadhesive properties due to in situ cross-linking between thiol groups of polymer and mucin [1].

Syntheses and Characterization of Two Diiron Dithiolate Complexes with Electron-withdrawing and Electron-donating Substitution

Two diiron dithiolate complexes [Fe2（CO）6（1,8-S2-2-CH2OOCPhC（10）H5）] 1 and[Fe2（CO）6（1,8-S2-2-CH2OOCPh-4-NO2C（10）H5）]2 were synthesized in high yield. The complexes have been confirmed by single-crystal X-ray diffraction and characterized by IR, UV-Vis, ^1H NMR spectroscopy and cyclic voltammetry. They contain a butterfly Fe2S2 core with the Fe1–Fe2 distances of 2.5237（7）A in 1 and 2.5125（12）A in 2, falling in the normal range of Fe–Fe bond length（2.49 - 2.57 A）. The cyclic voltammetry has been used to investigate the electrochemical properties and the electrocatalytic proton reduction for 1 and 2. The complexes display reduction peaks at –1.074 V, –1.535 V（1） and –0.869 V, –1.247 V（2） vs. Fc/Fc^＋, respectively. With using p-Ts OH acid of different concentration, the reduction peak of complex 2 grows non-linear; on the contrary, that of complex 1 is linear with the addition of the acid. Cyclic voltammetry revealed the two complexes are good catalysts in the CH3CN/NBu4PF6 solution.

Single thiolate replacement of metal nanoclusters

Surface thiolates play important roles in evincing the structures and properties of thiolated metal nanoclusters—one type of recently emerging inorganic-organic hybrids,and thus the thiolate substitution,especially single thiolate substitution,is highly desirable for subtly tailoring the structures and properties of metal nanoclusters.However,such a single-thiolate substituting is challenging,and its influence on the metal-metal and metal-sulfur bonds remains mysterious due to the absence of the singlethiolate-substituted structure.Here,we developed a combined method,concurrently synthesized the single-thiolate-substituted nanocluster and its parent nanocluster,and successfully resolved their structures by single crystal X-ray crystallography,which reveals that the single thiolate substitute has an obvious influence on the metal-metal and metal-sulfur bond lengths although it has no effect on the absorption profile.Interestingly,the metal-metal and metal-sulfur bonds show various thermal extensibility and even the negative thermal expansion phenomena of the Au–S bond were observed in the single-thiolate-substituted nanocluster.The bond length-related stability was also observed.Overall,this study highlights a novel synthesis method and offers novel structural insights and an in-depth structure-property correlation of thiolated metal nanoclusters.

Efficient capture of difluorocarbene by pyridinium 1,4-zwitterionic thiolates:A concise synthesis of difluoromethylene-containing 1,4-thiazine derivatives

A practical method for the construction of difluoromethylene-containing 1,4-thiazine moieties using readily available diethyl bromodifluoromethanephosphonate(BrCF_(2)PO(OEt)_(2))as difluorocarbene precusor has been developed.This transformation features the efficient capture of difluorocarbene by pyridinium 1,4-zwitterionic thiolates.A series of structurally novel and functionalized difluoromethylene-containing 1,4-thiazine derivatives were thus synthesized in good yields.

Solvent-driven reversible transformation between electrically neutral thiolate protected Ag_(25)and Ag_(26)clusters

Two atom-precise silver nanoclusters[Ag_(25)Cl_2(Tab)_(14)(Ph COO)_(11)(DMF)_4](PF_6)_(12)(Ag_(25),DMF=N,N-dimethylformamide)and[Ag_(26)Cl_2(Tab)_(14)(Ph COO)_(13)(DMAc)_4](PF_6)_(11)(Ag_(26),DMAc=N,N-dimethylacetamide)were synthesized based on the electrically neutral thiolate protective ligand,4-(trimethylammonio)benzenethiolate(Tab).The weak Ag–S interaction in Tab-protected silver nanoclusters allows to insert or leave a single silver atom in the Ag–S skeleton through solvent-trigger core fragmentation and re-arrangement,thereby realizing the reversible conversion of Ag_(25)and Ag_(26)for the first time.

Temperature-dependent chloride-mediated access to atom-precise silver thiolate nanoclusters

By using a unique temperature-dependent,chloride-mediated approach,two atom-precise silver nanoclusters[Cl@Ag_(14)(Tab)_(12)-(C_(5)H_(4)NCl)_(12)](PF_(6))_(13)(Cl@Ag_(14))and[Cl_(3)@Ag_(24)(Tab)_(20)(C_(5)H_(4)NCl)_(11)]Cl(PF_(6))_(20)(Cl_(3)@Ag_(24))(Tab=4-(trimethylammonio)benzenethiolate,C_(5)H_(4)NCl=3-chloropyridine)were obtained successfully.Notably,the number of chloride ions encapsulated inside the Ag-S shell could be regulated by the slow dissolution of almost insoluble KCl at various temperatures.The inclusion of additional core chloride ions results in the expansion of the surrounding Ag-S shell.This article provides a promising synthetic approach for controlling the number of Ag atoms that form a shell around the anionic core,in addition to offering a potential pathway for the introduction of other inorganic anions into silver clusters.More broadly,through the use of related ligands,the synthetic strategy offers scope for generating new families of silver thiolate clusters of varying size and composition.

Lanthanide Thiolate Complexes： Novel Initiators for Ring-opening Polymerization of ε-Caprolactone

The ring-opening polymerization （ROP） of ε-caprolactone （ε-CL） using lanthanide thiolate complexes [（CH3CsH4）2Sm（μ-SPh）（THF）]2 （1） and Sm（SPh）3（HMPA）3 （2） as initiators has been investigated for the first time. Both of 1 and 2 were found to be highly efficient initiators for the ROP of ε-CL. The poly（ε-caprolactone） （PCL） with molecular weight Mn up to 1.97 ×10^5 and relatively narrow molecular weight distributions （1.20〈MW/Mn〈 2.00） have been obtained in high yield in the temperature range of 35-65℃. According to the polymer yield, 2 showed much higher activity than 1. However, the number-average molecular weight of PCL obtained with 2 was much lower than with 1. The possible polymerization mechanism of the ε-CL polymerization has been proposed based on the results of the end group analysis of the ε-CL oligomer.

Development of a modular, biocompatible thiolated gelatin microparticle platform for drug delivery and tissue engineering applications

The field of biomaterials has advanced significantly in the past decade.With the growing need for high-throughput manufacturing and screening,the need for modular materials that enable streamlined fabrication and analysis of tissue engineering and drug delivery schema has emerged.Microparticles are a powerful platform that have demonstrated promise in enabling these technologies without the need to modify a bulk scaffold.This building block paradigm of using microparticles within larger scaffolds to control cell ratios,growth factors and drug release holds promise.Gelatin microparticles(GMPs)are a well-established platform for cell,drug and growth factor delivery.One of the challenges in using GMPs though is the limited ability to modify the gelatin post-fabrication.In the present work,we hypothesized that by thiolating gelatin before microparticle formation,a versatile platform would be created that preserves the cytocompatibility of gelatin,while enabling post-fabrication modification.The thiols were not found to significantly impact the physicochemical properties of the microparticles.Moreover,the thiolated GMPs were demonstrated to be a biocompatible and robust platform for mesenchymal stem cell attachment.Additionally,the thiolated particles were able to be covalently modified with a maleimide-bearing fluorescent dye and a peptide,demonstrating their promise as a modular platform for tissue engineering and drug delivery applications.

Anion-templated Self-assembly for the Preparation of Silver-t-butylthiolate Clusters

Silver thiolate polymers are intercepted to form different structural fragments when reacting with variant solubilizing reagents,which usually serve as the starting point for the preparation of clusters.However,such a process is still far from clear.Herein,we report the controlled synthesis of silver-t-butylthiolate clusters from reactions of polymeric[Ag^(t)BuS]n and suitable templates in the presence of solubilizing reagents to offer a detailed look at the mechanism of cluster’s formation.As the provided solubilizing reagents have weak coordina-tion ability,such as O-or N-donating ligands,the obtained polymeric compound retains the linear structure pat-tern that S and Ag atoms are arranged alternately.When extra templates NO_(3)^(−)and CO_(3)^(2−)are applied,the disk-like clusters Ag_(19)and Ag_(20)are constructed with the same[Ag^(t)BuS]_(5)circles that may directly cyclize from the linear[Ag^(t)BuS]_(n)fragments.In contrast,(EtO)_(2)PS_(2)^(−)and(iPrO)_(2)PS_(2)^(−)anions have large size and strong coordination abil-ity rendering the structure of the polymer completely fragmented.Thus extremely short[Ag^(t)BuS]n pieces with silver ions and solubilizing ligands assemble around the templates V_(2)O_(7)^(4−)and W_(2)O_(9)^(4−),leading to the formation of clusters Ag_(22)and Ag_(24).

Synthesis of tetrasubstituted thiophenes from pyridinium 1,4-zwitterionic thiolates and modified activated alkynes

Pyridinium 1,4-zwitterionic thiolates were applied to a formal [3+2] annulation reaction with modified activated alkynes, affording various tetrasubstituted thiophenes with aryl, alkenyl, alkyl or silyl group at the special position. The structural modification of alkyne substrates enabled the synthesis of diverse thiophenes to be achieved using the pyridinium 1,4-zwitterionic thiolates as the sulfur-containing building blocks. This approach is metal-free and catalyst-free.

Synthesis of Novel Binuclear Samarium Thiolate Complexes [（THF）3I2Sm（μ-SAr）]2 （Ar=Ph, 4-Me2NC6H4） and Crystal Structure of [（THF）3I2Sm（μ-S-4-Me2NC6H4）]2

Reactions of SmI2 in THF with ArSSAr produced two binuclear samarium thiolate complexes [（THF）3I2- Sm（μ-SAr）]2 [Ar=Ph （1）, 4-Me2NC6H4 （2）] in high yields. The structure of 2 was characterized by single crystal X-ray crystallography. The crystal of 2 belongs to the triclinic system with space group P 1 and a=0.95705（13） nm, b= 1.22287（14） nm, c= 1.26450（14） nm, a=64.194（11）°, B=78.491（13）°, y=76.176（12）°, V= 1.2860（3） nm^3, Z= 1,μ=4.783 mm^-1, Dc= 1.964 Mg/m^3, M= 1521.19, S= 1.046, R1=0.0358, wR2=0.0910. X-ray analysis revealed that 2 is a thiolate-bridged dimer in which each Sm atom adopts a distorted pentagonal bipyramidal coordi- nation geometry.

Atomically precise thiolate-protected gold nanoclusters:Current status of designability of the structure and physicochemical properties

Thiolate(SR)-protected gold nanoclusters(Aun(SR)m NCs)are a rare type of material capable of simultaneously exhibiting multiple physicochemical properties well-suited to specific applications,including photoluminescence,thermocatalysis,electrocatalysis,photocatalysis,magnetism,and optical activity.Over the past several decades,there has been tremendous progress in our understanding of the structure and physicochemical properties of Aun(SR)m NCs,resulting in the ability to fine-tune the characteristics of these materials.It is therefore helpful to examine the extent to which the properties of Aun(SR)m and related metal NCs can now be adjusted based on design.This review presents representative examples of previous studies concerning the geometry,electronic structure,luminescence properties,catalysis,magnetism and optical activity of Aun(SR)m and related metal NCs and discusses the current status of the designability of these NCs to impart specific structural and physicochemical characteristics.This information is expected to accelerate the fabrication of highly functional materials based on Aun(SR)m and related metal NCs.

Structural Evolution Patterns of FCC-Type Gold Nanoclusters

Recent progress in the research of atomically-precise metal nanoclusters has identified a series of exceptionally stable nanoclusters with specific chemical compositions. Structural determination on such "magic size" nanoclusters revealed a variety of unique structures such as decahedron, icosahedron, as well as hexagonal close packing(hcp) and body-centered cubic(bcc) packing arrangements in gold nanoclusters, which are largely different from the face-centered cubic(fcc) structure in conventional gold nanoparticles. The characteristic geometrical structures enable the nanoclusters to exhibit interesting properties, and these properties are in close correlation with their atomic structures according to the recent studies. Experimental and theoretical analyses have been applied in the structural identification aiming to clarify the universal principle in the structural evolution of nanoclusters. In this mini-review, we summarize recent studies on periodic structural evolution of fcc-based gold nanoclusters protected by thiolates. A series of nanoclusters exhibit one-dimensional growth along the [001] direction in a layer-by-layer manner from Au_(23)(TBBT)_(20) to Au_(36)(TBBT)_(24),Au_(44)(TBBT)_(28), and to Au_(52)(TBBT)_(32)(TBBT: 4-tert-butylbenzenethiolate). The optical properties of these nanoclusters also evolve periodically based on steady-state and ultrafast spectroscopy. In addition, two-dimensional growth from Au_(44)(TBBT)_(28) toward both [100] and [010] directions leads to the Au_(92)(TBBT)_(44) nanocluster, and the recently reported Au_(52)(PET)_(32)(PET: 2-phenylethanethiol) also follows this growth pattern with partial removal of the layer. Theoretical predictions of relevant fcc nanoclusters include Au_(60)(SCH_3)_(36), Au_(68)(SCH_3)_(40), Au_(76)(SCH_3)_(44), etc, for the continuation of 1 D growth pattern, as well as Au_(68)(SR)_(38)mediating the 2 D growth pattern from Au_(44)(TBBT)_(28) to Au_(92)(TBBT)_(44). Overall, this mini-review provides guidelines on the rules of structural evolution of fcc gold nanoclusters based on 1 D, 2 D and 3 D growth patterns.

Synthesis and Crystal Structure of N-phenylthiocyano-phenyl-thioformamide bis(η_5-methylcyclopentadienyl)(tetrahydrofuran)Samarium(Ⅲ)

The insertion reaction of phenyl isothiocyanate into the Ln S bond was studied. Phenyl isothiocyanate reacted with [(CH 3C 5H 4) 2Sm(SPh)(THF)] 2 to give the title complex, (CH 3C 5H 4) 2Sm[SC(SPh)NPh](THF), in good yield, which was characterized by elemental analyses, IR, 1H NMR and X ray structural determination. The crystal structure analysis of complex shows that samarium atom is coordinated by two CH 3C 5H 4 groups, one O atom of THF, and N and S atoms from the SC(SPh)NPh ligand to form a distorted trigonal bipyramidal geometry.

Synthesis and Thermal Stability of Antimony Tris (Thioethyl Stearate) for PVC

A novel type of thermal stabilizer-antimony tris (thioethyl stearate) (ATS) was synthsized. Its thermal stability was measured by heat-aging oven test when incorporated into PVC. ATS was synthesized from stearic acid, antimony trioxide and 2-mercaptoethanol in two steps. The reaction conditions of synthesis were optimized through orthogonal test. Experimental results show that the molar ratio of stearic acid and antimony tris (2-hydroxyethylthiolate) was 1.2, adding 0.6%tetra-n-butyl titanate as catalyst and xylene as azeotropic solvent, heating and refluxing for about 4 h, and the yield of ATS is 83.9%. The thermal stability time is about 40 min(at 200 °C) when added 2phr(per hundred resin) in PVC. The thermal stability of ATS is better than that of Ca-Zn complex and basic lead stabilizers, and equal to that of dibutyltin dilaurate.

Synthesis and Characterization of [(C_5H_4SiMe_2~tBu)_2Ln(μ-S^nBu)]_2 (Ln=Y,Er)

（C5H4SiMe2^tBu）2Ln^nBu reacted with 1 equiv, of elemental sulfur in toluene at ambient temperature to yield the corresponding lanthanocene thiolates [（C5H4SiMe2^tBu）2Ln（μ-S^nBu）]2 （Ln = Y （1）, Er （2））. Complexes 1 and 2 have been characterized by elemental analysis, IR, mass spectroscopy and X-ray single-crystal diffraction analysis. Both complexes are of monoclinic with space group P21/c, formula C52H94S2Si4Y2 1 （C52H94S2Si4Er2 2） Mr = 1073.57 （1230.27）, a = 8.495（2） （8.41（2））, b = 26.913（8） （26.67（7））, c = 13.756（4） （13.68（4）） A, α = 90（90）, β = 101.184（5） （101.57（4））, γ = 90 （90）°, V= 3085.1（15） （3007（14）） A^3, Dc = 1.156 （1.359） g·cm^-3, Z= 2 （2）, F（000） = 1144 （1260）, μ = 2.046 （2.951） cm^-1, R = 0.0687 （0.0749） and wR = 0.1306 （0.1507） for observed reflections with I 〉 2σ（I）. X-ray structures of 1 and 2 definitively prove that only one sulfur atom is inserted into the Ln-C（^nBu） bond, forming a thiolate ligand.

Synthesis and Structure of a Ruthenium(Ⅱ)-dithiocarbamate Complex [RuH(CO)(PPh_3)_2(4-ClPhNHCS_2)]·C_6H_(14)

The title complex [RuH（CO）（PPh3）2（4-ClPhNHCS2）]·C6H14 has been prepared and characterized by X-ray diffraction analysis.It crystallizes in the triclinic system,space group P1 with a = 11.0817（2）,b = 14.3889（2）,c = 15.2136（2） ,α = 71.018（1）,β = 74.911（1）,γ = 85.146（1）°,V = 2214.86（6） 3,Z = 2,Mr = 900.4,Dc = 1.350 g/cm3,Mr = 900.40,μ（MoKα） = 0.616 mm-1,F（000） = 926,S = 1.016,the final R = 0.0478 and wR = 0.0947 for 6828 observed reflections with I 2σ（I） and 505 variables.The molecular structure of 1 consists of one neutral complex [RuH（CO）（PPh3）2（4-ClPhNHCS2）] and one hexane solvent molecule.The geometry around ruthenium is pseudo-octahedral with two trans-binding PPh3 ligands and one chelating bidentate 4-ClPhNHCS2- ligand via two sulfur atoms.The average Ru-S,Ru-P and Ru-H bond lengths are 2.4824（8）,2.3495（8） and 1.71（2）,respectively.The electrochemical properties of 1 have been studied in CH2Cl2 solution by cyclic voltammetry.

Synthesis and Crystal Structure of a Heterometallic Trinuclear Ni/Ag/S Compound

A new tri-nuclear mixed metal thiolate complex [Ag（PPh3）2]2[Ni（edtO2）2] 1 has been synthesized and structurally characterized by single-crystal diffraction.The molecule has a crystallographic inversion centre occupied in the central Ni（II） atom and the two silver（I） atoms are related by the inversion centre.The unique structural feature is that one of thiolates of each edt ligand has been oxidized to sulfinate from the precursor [Ni（edt）2]2-to the neutral linear trinuclear complex.The crystal structure belongs to the monoclinic system,space group P21/n with a = 13.581（11）,b = 12.239（9）,c = 22.316（17） ,β = 103.08（2）o,V = 3613（5） 3,Z = 2,Mr = 1571.87,Dc = 1.445 g/cm3,μ = 1.046 mm-1,F（000） = 1604,T = 293（2） K,the final R = 0.0652 and wR = 0.1499 for 6776 observed reflections with I 2σ（I）.