Synthetic Blocks Research Articles

Synthesis of mesoporous silica spheres utilizing in tandem with POSS-based block copolymer and anion surfactant as dual-template

In this work, novel mesoporous silica spheres were prepared by calcination of golf-shaped silica microspheres, which were fabricated via a typical sol-gel method by using synthetic amphiphilic block copolymer poly(acrylate isobutyl polyhedral oligomeric silsesquioxane)-b-poly(dimethylaminoethyl methacrylate co-styrene)) (PAPOSS-b-(PDMAEMA-co-PSt) and anionic surfactant sodium dodecyl sulfate (SDS) as dual-template. Firstly, three different POSS-based block copolymers were synthesized through subsequent homopolymerization of acrylate isobutyl POSS and chain extension of dimethylaminoethyl methacrylate (DMAEMA) and styrene with various feed ratios via reversible transfer radical polymerization (RAFT). These amphiphilic block polymers and SDS were utilized as cooperative template to golf-shaped silica microspheres. The electrostatic interaction between protonated PDMAEMA segments and anion surfactant as well as the strong interaction between PAPOSS segments and silicon source plays the dominant role in forming golf-shaped silica spheres. Moreover, the surface morphology of silica spheres can be tuned by varying molar ratio of PDMAEMA/PAPOSS. The resulting golf-shaped silica microspheres were further calcined to give mesoporous silica spheres which exhibited a BET surface area of 1031 m2 g−1, a total pore volume of 0.826 cm3 g−1, and a narrow pore size distribution centered at 3.20 nm.

Fluorine-containing polyamphiphiles of block structure constructed of synthetic and biopolymer blocks

Fluorine-containing polyamphiphiles of block structure constructed of synthetic and biopolymer blocks

Comparative Histological and Histomorphometric Results of Six Biomaterials Used in Two-Stage Maxillary Sinus Augmentation Model after 6-Month Healing.

Objectives To evaluate the performances of six different bone substitute materials used as graft in maxillary sinus augmentation by means of histological and histomorphometric analysis of bone biopsies retrieved from human subjects after a 6-month healing period. Materials and Methods Six consecutive patients (3 males, 3 females, aged 50-72 years), healthy, nonsmokers, and with good oral hygiene, presenting edentulous posterior maxilla with a residual bone crest measuring ≤ 4 mm in vertical height and 3 to 5 mm in horizontal thickness at radiographic examination, were selected to receive sinus augmentation and delayed implant placement. Under randomized conditions, sinus augmentation procedures were carried out using mineralized solvent-dehydrated bone allograft (MCBA), freeze-dried mineralized bone allograft (FDBA), anorganic bovine bone (ABB), equine-derived bone (EB), synthetic micro-macroporous biphasic calcium-phosphate block consisting of 70% beta-tricalcium phosphate and 30% hydroxyapatite (HA-β-TCP 30/70), or bioapatite-collagen (BC). After 6 months, bone core biopsies were retrieved and 13 implants were placed. Bone samples were processed for histological and histomorphometric analysis. CT scans were taken before and after surgery. After 4 months of healing, patients were restored with a provisional fixed acrylic resin prosthesis, as well as after further 2-4 months with a definitive cemented zirconia or porcelain-fused-to-metal crowns. Results There were no postoperative complications or implant failures. The histological examination showed that all biomaterials were in close contact with newly formed bone, surrounding the graft granules with a bridge-like network. No signs of acute inflammation were observed. The histomorphometry revealed 20.1% newly formed bone for MCBA, 32.1% for FDBA, 16.1% for ABB, 22.8% for EB, 20.3% for HA-β-TCP 30/70, and 21.4% for BC. Conclusions Within the limitations of the present investigation, all the six tested biomaterials showed good biocompatibility and osteoconductive properties when used in sinus augmentation procedures, although the FDBA seemed to have a better histomorphometric result in terms of newly formed bone and residual graft material. This trial is registered with ClinicalTrials.gov Identifier (Registration Number): NCT03496688.

Analysis of matrix effect in laser ablation inductively coupled plasma mass spectrometry for rhyolitic glass: Critical evaluation with new Aso-4 b-W synthetic glass blocks

Analysis of matrix effect in laser ablation inductively coupled plasma mass spectrometry for rhyolitic glass: Critical evaluation with new Aso-4 b-W synthetic glass blocks

Highly filled biocomposites based on ethylene-vinyl acetate copolymer and wood flour

Recently, there is a great interest in the world to biodegradable materials based on synthetic polymers in a composition with natural fillers. Highly filled polymer composite materials based on various grades of synthetic block copolymer of ethylene vinyl acetate with wood flour were under investigation. Five grades of ethylene-vinyl acetate copolymer differing in the content of vinyl acetate groups and a melt flow index were used in this work in order to find the best one for highly filled biocomposites. Wood flour content in biocomposites was 50, 60, 70 weight %. The rheological and physico-mechanical characteristics of the resulting biocomposites were studied.

Increased torsional stability by a novel femoral neck locking plate. The role of plate design and pin configuration in a synthetic bone block model

BackgroundIn undisplaced femoral neck fractures, internal fixation remains the main treatment, with mechanical failure as a frequent complication. As torsional stable fixation promotes femoral neck fracture healing, the Hansson Pinloc® System with a plate interlocking pins, was developed from the original hook pins. Since its effect on torsional stability is undocumented, the novel implant was compared with the original configurations. MethodsForty-two proximal femur models custom made of two blocks of polyurethane foam were tested. The medial block simulated the cancellous head, while the lateral was laminated with a glass fiber filled epoxy sheet simulating trochanteric cortical bone. Two hollow metal cylinders with a circumferential ball bearing in between mimicked the neck, with a perpendicular fracture in the middle. Fractures were fixated by two or three independent pins or by five configurations involving the interlocking plate (two pins with an optional peg in a small plate, or three pins in a small, medium or large plate). Six torsional tests were performed on each configuration to calculate torsional stiffness, torque at failure and failure energy. FindingsThe novel configurations improved parameters up to an average of 12.0 (stiffness), 19.3 (torque) and 19.9 (energy) times higher than the original two pins (P < 0.001). The plate, its size and its triangular configuration improved all parameters (P = 0.03), the plate being most effective, also preventing permanent failure (P < 0.001). InterpretationThe novel plate design with its pin configuration enhanced torsional stability. To reveal clinical relevance a clinical study is planned.

Site-Specific DBCO Modification of DEC205 Antibody for Polymer Conjugation.

The design of multifunctional polymer-based vectors, forming pDNA vaccines, offers great potential in cancer immune therapy. The transfection of dendritic immune cells (DCs) with tumour antigen-encoding pDNA leads to an activation of the immune system to combat tumour cells. In this work, we investigated the chemical attachment of DEC205 antibodies (aDEC205) as DC-targeting structures to polyplexes of P(Lys)-b-P(HPMA). The conjugation of a synthetic block copolymer and a biomacromolecule with various functionalities (aDEC205) requires bioorthogonal techniques to avoid side reactions. Click chemistry and in particular the strain-promoted alkyne-azide cycloaddition (SPAAC) can provide the required bioorthogonality. With regard to a SPAAC of both components, we firstly synthesized two different azide-containing block copolymers, P(Lys)-b-P(HPMA)-N3(stat) and P(Lys)-b-P(HPMA)-N3(end), for pDNA complexation. In addition, the site-specific incorporation of ring-strained dibenzocyclooctyne (DBCO) moieties to the DEC205 antibody was achieved by an enzymatic strategy using bacterial transglutaminase (BTG). The chemical accessibility of DBCO molecules within aDEC205 as well as the accessibility of azide-functionalities on the polyplex’ surface were investigated by various SPAAC experiments and characterized by fluorescence correlation spectroscopy (FCS).

Signal Dependent Transform Based on SVD for HEVC Intracoding

Transform is used to compact the energy of the blocks into a small number of coefficients and is widely used in recent image/video coding standards. In the latest video coding standard high efficiency video coding (HEVC), a combination of discrete cosine transform (DCT) and discrete sine transform (DST) is adopted to transform the residuals from intra prediction. Since the DCT and DST are the fixed transforms that are derived from the Gauss–Markov model, some of residual blocks may not be compacted well by the DCT/DST. In this paper, we propose a signal dependent transform based on singular value decomposition (SVD) for HEVC intracoding. The proposed transform (SDT-SVD) is derived by performing SVD on the synthetic block and applied to the residual block considering the structural similarity between them. Furthermore, we extend SDT-SVD to template matching prediction (TMP) to further improve the intracoding performance. Experimental results show that the proposed transform on angular intra prediction (AIP) outperforms the latest HEVC reference software with a bit rate reduction of 1.0% on average and it can be up to 2.1%. When the proposed transform is extended to TMP-based intracoding, the overall bit rate reduction is 2.7% on average and can be up to 5.8%.

Transparent Pullulan/Mica Nanocomposite Coatings with Outstanding Oxygen Barrier Properties.

This study presents a new bionanocomposite coating on poly(ethylene terephthalate) (PET) made of pullulan and synthetic mica. Mica nanolayers have a very high aspect ratio (α), at levels much greater than that of conventional exfoliated clay layers (e.g., montmorillonite). A very small amount of mica (0.02 wt %, which is ϕ ≈ 0.00008) in pullulan coatings dramatically improved the oxygen barrier performance of the nanocomposite films under dry conditions, however, this performance was partly lost as the environmental relative humidity (RH) increased. This outcome was explained in terms of the perturbation of the spatial ordering of mica sheets within the main pullulan phase, because of RH fluctuations. This was confirmed by modelling of the experimental oxygen transmission rate (OTR) data according to Cussler’s model. The presence of the synthetic nanobuilding block (NBB) led to a decrease in both static and kinetic coefficients of friction, compared with neat PET (≈12% and 23%, respectively) and PET coated with unloaded pullulan (≈26% reduction in both coefficients). In spite of the presence of the filler, all of the coating formulations did not significantly impair the overall optical properties of the final material, which exhibited haze values below 3% and transmittance above 85%. The only exception to this was represented by the formulation with the highest loading of mica (1.5 wt %, which is ϕ ≈ 0.01). These findings revealed, for the first time, the potential of the NBB mica to produce nanocomposite coatings in combination with biopolymers for the generation of new functional features, such as transparent high oxygen barrier materials.

Recent progress on DNA block copolymer

DNA has gained great attention because of its unique structure, excellent molecular recognition property, and biological functions. When married with versatile synthetic polymers, the DNA conjugated polymer hybrids, known as DNA block copolymers (DBCs), have been launched and well developed for the syntheses of new materials and nanostructures with different functions in the past several decades. Compared to conventional synthetic block copolymers, using DNA as a building block provides several advantages over other polymer candidates, such as molecular recognition, programmable self-assembly, biocompatibility, and sequence-encoded information. In this review, recent developments in this area will be summarized and meaningful breakthroughs will be highlighted. We will discuss representative examples of recent progress in the syntheses, structure manipulations, and applications of DBCs.

Comparative evaluation of insertion torque and mechanical stability for self-tapping and self-drilling orthodontic miniscrews \u2013 an in vitro study

BackgroundThe aim of the present study was to evaluate the relationship between insertion torque and stability of miniscrews in terms of resistance against dislocation, then comparing a self-tapping screw with a self-drilling one.MethodsInsertion torque was measured during placement of 30 self-drilling and 31 self-tapping stainless steel miniscrews (Leone SpA, Sesto Fiorentino, Italy) in synthetic bone blocks. Then, an increasing pulling force was applied at an angle of 90° and 45°, and the displacement of the miniscrews was recorded.ResultsThe statistical analysis showed a statistically significant difference between the mean Maximum Insertion Torque (MIT) observed in the two groups and showed that force angulation and MIT have a statistically significant effect on miniscrews stability. For both the miniscrews, an angle of 90° between miniscrew and loading force is preferable in terms of stability.ConclusionsThe tested self-drilling orthodontic miniscrews showed higher MIT and greater resistance against dislocation than the self-tapping ones.

The usage of combination of tricalcium phosphate and polylactic acid as materials for 3D printing of alloplastic blocks

This study describes the manufacturing method of alloplastic blocks for treatment of bone defects through tissue replacement with combination of tricalcium phosphate and polylactic acid. The method is unique because for its implementation we used 3d-printing and materials that we had not combined before. Such approach to manufacturing of synthetic blocks allows us to decide several tasks: planning of surgical operation’s strategy by means of modelling in specialized software of certain operating region and to print block with suitable shape and size which would accurately fit the edges of bone defects and fill it. Thus, we can achieve all objectives in the shortest possible time, while saving time and resources. Using this methods, we created experimental model of lower jaw and alloplastic block that can be used with a real patient and be widely applied not only in surgical dentistry and maxillofacial surgery, but also in any other branch of medicine.Combination of tricalcium phosphate and polylactic acid has several advantages because first component acts as a frame and due to its chemical structure makes block’s shape more stable. The second component acts as a filler by means of irregular shape of granules and creates spongiform structure for further blood vessels growth. In addition, materials have properties such as: bioinertness, biocompatibility, biodegradable and don’t have negative impact on the organism. Using this method, we can get the fragment that meets all requirements, and surgical operation becomes economically profitable both for patient and for hospital.

DNA Topoisomerase II modulates acetyl-regulation of cohesin-mediated chromosome dynamics.

Cohesin is one of three multi-protein structural maintenance of chromosome (SMC) complexes that regulate eukaryotic chromosome dynamics. It forms a ring-shaped structure that embraces sister chromatids through interphase to promote their pairing. In preparation for mitosis, most cohesin is stripped from the chromosome arms in prophase by a poorly defined process that is associated with cohesin phosphorylation. In the fission yeast Schizosaccharomyces pombe this prophase pathway is dependent on the cohesin-related Smc5/6 complex, and this requirement is heightened in Smc5/6 hypomorphs by DNA damage, replication stress and Topoisomerase II (Top2) dysfunction. Cohesin interacts with chromosomes immediately upon mitotic exit and becomes cohesive coincident with DNA replication. Cohesiveness is promoted by acetylation of the Smc3 subunit by an acetyltransferase, known as Eso1 in the S. pombe, which counteracts the anti-cohesive function(s) of the cohesin regulators Pds5 and Wpl1. We recently showed that Eso1 and Smc5/6 antagonize each other, and concurrent inactivation restores sister chromatid separation following genotoxic stress. Here, we have investigated the relationship between Top2 and Eso1 in successful completion of mitosis. We observe that partial inactivation of both results in a synthetic lethal mitotic block, but this is not overcome by deleting pds5 or wpl1. However, analysis of both acetyl-blocking and mimetic mutations in Smc3 indicates that the cycling of cohesin acetyl-regulation is more important than acetyl-status per se, highlighting the non-linear nature of the cohesin cycle.

Ligand-decorated click polypeptide derived nanoparticles for targeted drug delivery applications

A ligand decorated, synthetic polypeptide block copolymer platform with environment-responsive capabilities was designed. We evaluated the potential of this system to function as a polymersome for targeted-delivery of a systemic chemotherapy to tumors. Our system employed click chemistry to provide a pH-responsive polypeptide block that drives nanoparticle assembly, and a ligand (folic acid) conjugated PEG block that targets folate-receptor over-expressing cancer cells. These nanocarriers were found to encapsulate a high loading of conventional chemotherapeutics (e.g. doxorubicin at physiological pH) and release the active therapeutic at lysosomal pH upon cellular uptake. The presence of folic acid on the nanoparticle surface facilitated their active accumulation in folate-receptor-overexpressing cancer cells (KB), compared to untargeted carriers. Folate-targeted nanoparticles loaded with doxorubicin also showed enhanced tumor accumulation in folate-receptor positive KB xenografts, resulting in the suppression of tumor growth in an in vivo hind flank xenograft mouse model.

Amino Acid Block Copolymers with Broad Antimicrobial Activity and Barrier Properties.

Antimicrobial properties of a long-chain, synthetic, cationic, and hydrophobic amino acid block copolymer are reported. In 5 and 60 min time-kill assays, solutions of K100 L40 block copolymers (poly(l-lysine·hydrochloride)100 -b-poly(l-leucine)40 ) at concentrations of 10-100 µg mL-1 show multi-log reductions in colony forming units of Gram-positive and Gram-negative bacteria, as well as yeast, including multidrug-resistant strains. Driven by association of hydrophobic segments, K100 L40 copolymers form viscous solutions and self-supporting hydrogels in water at concentrations of 1 and 2 wt%, respectively. These K100 L40 preparations provide an effective barrier to microbial contamination of wounds, as measured by multi-log decreases of tissue-associated bacteria with deliberate inoculation of porcine skin explants, porcine open wounds, and rodent closed wounds with foreign body. Based on these findings, amino acid copolymers with the features of K100 L40 can combine potent, direct antimicrobial activity and barrier properties in one biopolymer for a new approach to prevention of wound infections.

Bioinspired Universal Monolayer Coatings by Combining Concepts from Blood Protein Adsorption and Mussel Adhesion.

Despite the increasing need for universal polymer coating strategies, only a few approaches have been successfully developed, and most of them are suffering from color, high thickness, or high roughness. In this paper, we present for the first time a universal monolayer coating that is only a few nanometers thick and independent of the composition, size, shape, and structure of the substrate. The coating is based on a bioinspired synthetic amphiphilic block copolymer that combines two concepts from blood protein adsorption and mussel adhesion. This polymer can be rapidly tethered on various substrates including both planar surfaces and nanosystems with high grafting density. The resulting monolayer coatings are, on the one hand, inert to the adsorption of multiple polymer layers and prevent biofouling. On the other hand, they are chemically active for secondary functionalization and provide a new platform for selective material surface modification.

Interfragmentary compression and pull-out properties of 6.5-mm AO cancellous lag screws in a uniform synthetic material during tightening procedures

AO lag screws are widely used in surgical intra-articular fracture treatment for anatomical reduction and rigid fixation. Interfragmentary compressive force (IFCF) and pull-out strength (POS) are two critical parameters generated by AO lag screws during tightening, and both of these parameters could be used to estimate screw insert conditions to prevent screw stripping. The aim of this study is to evaluate the IFCF and POS of AO cancellous screws inserted into uniform synthetic cancellous bone during tightening procedures. Seven synthetic cancellous bone blocks were used for this research. Each test contained two continuous portions as follows: the rotation test portion and the pull-out test portion. IFCF and POS were captured by the pressure transducer and the sensor of the test machine. The properties of IFCF and POS based on tightening degrees were obtained in this study. The ideal balance between POS and IFCF during screw tightening exists, and the peak values of these parameters cannot be simultaneously achieved. Moreover, rotation angles of 100–150° appear to serve as the optimum balance between IFCF and POS in the present study.

Experimental analysis of insertion torques and forces of threaded and press-fit acetabular cups by means of ex vivo and in vivo measurements.

In THA a sufficient primary implant stability is the precondition for successful secondary stability. Industrial foams of different densities have been used for primary stability investigations. The aim of this study was to analyse and compare the insertion behaviour of threaded and press-fit cups in vivo and ex vivo using bone substitutes with various densities. Two threaded (Bicon Plus®, Trident® TC) and one press-fit cup (Trident PSL®) were inserted by orthopaedic surgeons (S1, S2) into 10, 20 and 31 pcf blocks, using modified surgical instruments allowing measurements of the insertion forces and torques. Furthermore, the insertion behaviour of two cups were analysed intraoperatively. Torques for the threaded cups increased while bone substitute density increased. Maximum insertion torques were observed for S2 with 102 Nm for the Bicon Plus® in 20 pcf blocks and 77 Nm for the Trident® TC in 31 pcf blocks, which compares to the in vivo measurement (85 Nm). The average insertion forces for the press-fit cup varied from 5.2 to 6.8 kN (S1) and 7.2-11.5 kN (S2) ex vivo. Intraoperatively an average insertion force of 8.0 kN was determined. Implantation behaviour was influenced by acetabular cup design, bone substitute and experience of the surgeon. No specific density of bone substitute could be favoured for ex vivo investigations on the implantation behaviour of acetabular cups. The use synthetic bone blocks of high density (31 pcf) led to problems regarding cup orientation and seating. Therefore, bone substitutes used should be critically scrutinized in terms of the comparability to the in vivo situation.

Recent advances in the synthesis of fungal antigenic oligosaccharides

Abstract The driving force for the constant improvement and development of new synthetic methodologies in carbohydrate chemistry is a growing demand for biologically important oligosaccharide ligands and neoglycoconjugates thereof for numerous biochemical investigations such as cell-to-pathogen interactions, immune response, cell adhesion, etc. Here we report our syntheses of the spacer-armed antigenic oligosaccharides related to three groups of the polysaccharides of the fungal cell-wall including α- and β-mannan, α- and β-glucan and galactomannan chains, which include new rationally designed synthetic blocks, efficient solutions for the stereoselective construction of glycoside bonds, and novel strategy for preparation of furanoside-containing oligosaccharides based on recently discovered pyranoside-into-furanoside (PIF) rearrangement.

Split-Intein Triggered Protein Hydrogels.

Proteins are nature's building blocks and indispensable in living organisms. Protein-based hydrogels have a wide variety of applications in research and biotechnology. In this chapter, we describe an intein-mediated protein hydrogel that utilizes two synthetic soluble protein block copolymers, each containing a subunit of a trimeric protein that serves as a cross-linker and one half of the naturally split DnaE intein from Nostoc punctiforme. Mixing of these two protein block copolymers initiates an intein trans-splicing reaction that constitutes a self-assembling polypeptide flanked by cross-linkers, triggering protein hydrogel formation. The generated hydrogels are highly stable under both acidic and basic conditions, and at temperatures up to 50 °C. In addition, these hydrogels are able to undergo rapid reassembly after shear-induced rupture. Incorporation of an appropriate binding motif into the protein block copolymers enables the convenient site-specific incorporation of functional globular proteins into the hydrogel network.