RESUMEN
Five new anthraquinone derivatives, auxarthrols D-H (1-5), along with two known analogues (6-7), were obtained from the culture of the marine-derived fungus Sporendonema casei. Their structures, including absolute configurations, were established on the basis of NMR, HRESIMS, and circular dichroism (CD) spectroscopic techniques. Among them, compound 4 represents the second isolated anthraquinone derivative with a chlorine atom, which, with compound 6, are the first reported anthraquinone derivatives with anticoagulant activity. Compounds 1 and 3 showed cytotoxic activities with IC50 values from 4.5 µM to 22.9 µM, while compounds 1, 3-4, and 6-7 showed promising antibacterial activities with MIC values from 12.5 µM to 200 µM. In addition, compound 7 was discovered to display potential antitubercular activity for the first time.
Asunto(s)
Antraquinonas/química , Antraquinonas/farmacología , Ascomicetos/química , Antraquinonas/aislamiento & purificación , Antibacterianos/química , Antibacterianos/aislamiento & purificación , Antibacterianos/farmacología , Anticoagulantes/química , Anticoagulantes/farmacología , Organismos Acuáticos/química , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Dicroismo Circular , Humanos , Concentración 50 Inhibidora , Espectroscopía de Resonancia Magnética , Pruebas de Sensibilidad MicrobianaRESUMEN
Three new azaphilone alkaloids containing glutamine residues, namely N-glutarylchaetoviridins A-C (1-3), together with two related compounds (4 and 5) were isolated from the extract of Chaetomium globosum HDN151398, a fungus isolated from a deep-sea sediment sample collected in South China Sea. Their structures were elucidated on the basis of extensive 1D and 2D NMR as well as HRESIMS spectroscopic data and chemical analysis. N-glutarylchaetoviridins A-C (1-3) represent the first class of chaetoviridins characterized by embedded glutamate residues. Amino acids incubation experiments produced five azaphilone laden different amino acids residues (6-10) which indicated that this method can enhanced the structural diversity of this strain by culturing with amino acids. Cytotoxicity of the isolated compounds were evaluated against a panel of human cancer cell lines.
Asunto(s)
Alcaloides/farmacología , Antineoplásicos/farmacología , Benzopiranos/farmacología , Chaetomium/química , Sedimentos Geológicos/microbiología , Pigmentos Biológicos/farmacología , Alcaloides/química , Alcaloides/aislamiento & purificación , Antineoplásicos/química , Antineoplásicos/aislamiento & purificación , Organismos Acuáticos/química , Benzopiranos/química , Benzopiranos/aislamiento & purificación , Línea Celular Tumoral , Ensayos de Selección de Medicamentos Antitumorales , Glutamina/química , Humanos , Concentración 50 Inhibidora , Espectroscopía de Resonancia Magnética , Estructura Molecular , Pigmentos Biológicos/química , Pigmentos Biológicos/aislamiento & purificaciónRESUMEN
Resistance to the proteasome inhibitor bortezomib is an emerging clinical problem whose mechanisms have not been fully elucidated. We considered the possibility that this could be associated with enhanced proteasome activity in part through the action of the proteasome maturation protein (POMP). Bortezomib-resistant myeloma models were used to examine the correlation between POMP expression and bortezomib sensitivity. POMP expression was then modulated using genetic and pharmacologic approaches to determine the effects on proteasome inhibitor sensitivity in cell lines and in vivo models. Resistant cell lines were found to overexpress POMP, and while its suppression in cell lines enhanced bortezomib sensitivity, POMP overexpression in drug-naive cells conferred resistance. Overexpression of POMP was associated with increased levels of nuclear factor (erythroid-derived 2)-like (NRF2), and NRF2 was found to bind to and activate the POMP promoter. Knockdown of NRF2 in bortezomib-resistant cells reduced POMP levels and proteasome activity, whereas its overexpression in drug-naive cells increased POMP and proteasome activity. The NRF2 inhibitor all-trans-retinoic acid reduced cellular NRF2 levels and increased the anti-proliferative and pro-apoptotic activities of bortezomib in resistant cells, while decreasing proteasome capacity. Finally, the combination of all-trans-retinoic acid with bortezomib showed enhanced activity against primary patient samples and in a murine model of bortezomib-resistant myeloma. Taken together, these studies validate a role for the NRF2/POMP axis in bortezomib resistance and identify NRF2 and POMP as potentially attractive targets for chemosensitization to this proteasome inhibitor.
Asunto(s)
Bortezomib/uso terapéutico , Resistencia a Antineoplásicos , Chaperonas Moleculares/fisiología , Mieloma Múltiple/tratamiento farmacológico , Factor 2 Relacionado con NF-E2/fisiología , Línea Celular Tumoral , Humanos , Tretinoina/farmacologíaRESUMEN
Multiple myeloma (MM) is characterized by the impaired osteogenic differentiation of mesenchymal stromal cells (MSCs). However, the underlying molecular mechanisms are still poorly understood. Long noncoding RNAs (lncRNAs) are emerging as important regulatory molecules in tumor-suppressor and oncogenic pathways. Here we showed that MSCs from MM expressed less lncRNA MEG3 relative to those from normal donors during osteogenic differentiation. To evaluate the effect of MEG3 on osteogenesis, bone marrow MSCs with enhanced or reduced MEG3 were prepared. We observed that MEG3 knockdown significantly reduced the expression of key osteogenic markers, including Runt-related transcription factor 2, osterix, and osteocalcin, while overexpression of MEG3 enhanced their expression. Additionally, MEG3 knockdown decreased BMP4 transcription. Here we showed that MEG3 was critical for SOX2 transcriptional repression of the BMP4. MEG3, which is located near the BMP4 gene, could dissociate the transcription factor SOX2 from the BMP4 promoter. A stable complex containing the MEG3, SOX2, and the SOX2 consensus site of BMP4 suggested that MEG3 activated transcriptional activity by directly influencing SOX2 activity. By using assays such as luciferase, chromatin immunoprecipitation, and RNA immunoprecipitation, we showed that MEG3 had a critical function in a mechanism of promoter-specific transcriptional activation. These results suggested that MEG3 played an essential role in osteogenic differentiation in bone marrow MSCs, partly by activating BMP4 transcription. Our data provided novel evidence for the biological and clinical significance of lncRNA MEG3 expression as a potential biomarker for identifying patients with MM and as a potential therapeutic target in MM.
Asunto(s)
Proteína Morfogenética Ósea 4/genética , Diferenciación Celular/genética , Células Madre Mesenquimatosas/citología , Mieloma Múltiple/metabolismo , ARN Largo no Codificante/metabolismo , Humanos , Mieloma Múltiple/genética , Mieloma Múltiple/patología , Osteogénesis/genética , ARN Largo no Codificante/genética , Factores de Transcripción SOXB1/genética , Factores de Transcripción SOXB1/metabolismo , Activación Transcripcional/genética , Regulación hacia ArribaRESUMEN
The polymerization kinetics of physically separated hydrophobic- and hydrophilic-rich phases of a model dental adhesive have been investigated. The two phases were prepared from neat resin containing 2-hydroxyethyl methacrylate (HEMA) and bisphenol A glycerolate dimethacrylate (BisGMA) in the ratio of 45:55 (wt/wt). Neat resins containing various combinations of popular photo-initiating compounds, e.g., camphoquinone (CQ), ethyl 4-(dimethylamino)benzoate (EDMAB), 2-(dimethylamino)ethyl methacrylate (DMAEMA) and diphenyliodonium hexafluorophosphate (DPIHP) were prepared. To obtain the two phases 33 wt% of deuterium oxide (D2O) was added to the neat resins. This amount of D2O exceeded the miscibility limit for the resins. The concentration of each component of the photo-initiating system in the two phases was quantified by HPLC. When combined with CQ, DMAEMA is less efficient as a co-initiator compared to EDMAB. The addition of DPIHP as the third component into either CQ/EDMAB or CQ/DMAEMA photo-initiating systems leads to comparable performance in both the hydrophobic- and hydrophilic-rich phases. The addition of the iodonium salt significantly improved the photopolymerization of the hydrophilic-rich phase; the hydrophilic-rich phase exhibited extremely poor polymerization when the iodonium salt was not included in the formulation. The partition concentration of EDMAB in the hydrophilic-rich phase was significantly lower than that of DMAEMA or DPIHP. This study indicates the need for a combination of hydrophobic/hydrophilic photosensitizer and addition of iodonium salt to improve polymerization within the hydrophilic-rich phase of the dental adhesive.
RESUMEN
A new tertiary amine co-initiator (TUMA) containing three methacrylate-urethane groups was synthesized for application in dentin adhesives. The photopolymerization kinetics and leaching of unreacted components from methacrylate-based dental polymers formulated with this new co-initiator were determined. The newly synthesize co-initiator showed good chemical stability and decreased amine release from the initiator system. This study provides important information for the future development of biocompatible dentin adhesives/composites.
RESUMEN
We report a graphene-based nanocomposite prepared by noncovalently engineering reduced graphene oxide (rGO) with neutral red (NR). The water-soluble reduced graphene nanocomposite (rGO-NR) was well characterized by using X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), UV-vis spectroscopy, and 1HNMR spectroscopy; the results suggest a strong pi-pi interaction between the rGO and NR molecules. Fluorescence spectroscopy and electrochemistry studies indicate a direct electron transfer interaction among the graphene-NR hybrid, in which NR is electron donor and graphene is electron acceptor. The photocurrent generating property of this nanocomposite was confirmed from the photoelectrochemical measurements. The graphene-NR coated electrodes are capable of generating photocurrent under visible excitation. Such photocurrent generating nanocomposite provides potential application in optoelectronic devices.
RESUMEN
BACKGROUND: Multiple myeloma (MM) can be accompanied by amyloidosis, which occurs in a small number of patients and is characterized by deposition of light chains in the joints, leading to multiple myeloma-associated amyloid arthropathy (MAA). As a rare complication of MM, clinical manifestations of MAA are often similar to those of rheumatoid arthritis, and the two are easily confused. CASE SUMMARY: In recent years, our center treated two patients of MM with amyloid arthropathy as the first manifestation, both of whom presented with polyarthritis. After treatment for MM, both patients achieved complete remission. However, subsequently, the two patients underwent hip arthroplasty for femoral neck fractures. Congo red staining and immunofluorescence of the joint tissues confirmed MAA after surgery. Eventually, one of the patients died of MM recurrence, while the other survived. CONCLUSION: MAA should be regarded as an initial symptom of MM and should be taken seriously.
RESUMEN
A facile approach is proposed to one-pot synthesis of two kinds of nanoparticles: a new type of PS nanobowls (a hole appearing at the bottom of nanobowl) and PS/silica hybrid multipod-like nanoparticles. The two type of nanoparticles generated together during polymerization could be separated easily by centrifugation. Furthermore, the structure of nanobowls could be easily controlled by the weight ratio of monomer/silica. In addition, we find that the multipod-like nanoparticles play important roles in hydrophobic properties. The water contact angle increased from 24.0° to 143.3° after coated with the multipod-like nanoparticles.
Asunto(s)
Nanopartículas/química , Polímeros/síntesis química , Emulsiones , Interacciones Hidrofóbicas e Hidrofílicas , Polimerizacion , Polímeros/química , Poliestirenos/química , Dióxido de Silicio/químicaRESUMEN
Novel walnut-like multihollow polymer particles were first prepared by gamma-ray radiation emulsion polymerization using cross-linked and sulfonated polystyrene spheres (CSPs) as the template. The formation process was studied in detail, and the morphology of walnut-like multihollow polystyrene particles could be controlled by the content of cross-linking agent, sulfonation time of CSP particles, and the weight ratio of monomer/CSP. In addition, an application of walnut multihollow polymer particles on bonding Ag nanoparticles onto the surface was achieved, which could be extended to other noble metal nanoparticles and could have a wide range of potential applications, such as catalysts, sensors, solar cells, and photonic crystals.
RESUMEN
Novel anisotropic hybrid particles with various morphologies have been synthesized by radiation miniemulsion polymerization for the first time.
RESUMEN
OBJECTIVE: To evaluated the effect of curcumin on the bortezomib-resistant myeloma cells and the expression of Notch1 signaling pathway, in order to further explore its potential mechanism. METHODS: Curcumin, bortezomib, and curcumin combined bortezomib were added into RPMI 8266, U266, 5 nmol/L bortezomib-resistant RPMI 8266 (RPMI 8226-V5R), 5 nmol/L bortezomib-resistant U 266 (U266-V5R) and CD138+ plasma cells respectively. The cell proliferation was measured by MTT assay. the apoptotic rate was determined by flow cytometry, and the Western blot was used to detect the expression of apoptosis-related proteins. Then, the expression of Notch1 in cells was inhibited by notch1 inhibitor DAPT and RNA interference, the above-motioned experiments should be repeated. RESULTS: Compared with single drug-treated groups, the treatment with 2 drugs could further inhibit cell proliferation, induce apoptosis and enhance the inhibition effect on notch1 signaling pathway (P<0.05), while the inhibiting Notch1 signaling pathway could reduce cell proliferation and increase the expression of cleaved caspase-3. CONCLUSION: Curcumin can increase chemosensitivity of myeloma cells to bortezomib, this effect may be related to the inhibition of Notch1.
Asunto(s)
Mieloma Múltiple , Apoptosis , Bortezomib , Línea Celular Tumoral , Proliferación Celular , Curcumina , Humanos , Receptor Notch1 , Transducción de SeñalRESUMEN
Resin-based composite has overtaken dental amalgam as the most popular material for direct restorative dentistry. In spite of this popularity the clinical lifetime of composite restorations is threatened by recurrent decay. Degradation of the adhesive leads to gaps at the composite/tooth interface-bacteria, bacterial by-products and fluids infiltrate the gaps leading to recurrent decay and composite restoration failure. The durability of resin-dentin bonds is a major problem. We address this problem by synthesizing silyl-functionalized BisGMA (e.g., silyl-BisGMA), formulating dental adhesives with the new monomer and determining the physicochemical properties and leaching characteristics of the silyl-BisGMA adhesives. Silyl-BisGMA was synthesized by stoichiometric amounts of BisGMA and 3-isocyanatopropyl trimethoxysilane (IPTMS). The control adhesive was a mixture based on HEMA/BisGMA (45/55, w/w). In the experimental formulations, BisGMA was partially or completely replaced by silyl-BisGMA. Water miscibility, polymerization behavior (Fourier transform infrared spectroscopy, FTIR), thermal property (modulated differential scanning calorimetry, MDSC), mechanical properties in dry and wet conditions (dynamic mechanical analysis, DMA), and leached species (HPLC) were investigated. Data from all tests were submitted to appropriate statistical analysis (αâ¯=â¯0.05). Silyl-BisGMA-containing adhesives exhibited comparable water miscibility, lower viscosities, and significantly improved degree of conversion of CC bond as compared to the control. After 4â¯weeks aqueous aging, the glass transition temperature and rubbery moduli of the experimental copolymers were significantly greater than the control (pâ¯<â¯0.05). HPLC results indicated a substantial reduction of leached HEMA (up to 99â¯wt%) and BisGMA (up to 90â¯wt%). By introducing silyl-functional group, the new BisGMA derivative exhibited potential as a monomer that can lead to dental adhesives with improved mechanical properties and reduced leaching under conditions relevant to the oral environment. STATEMENT OF SIGNIFICANCE: The low-viscosity adhesive that bonds the composite to the tooth (enamel and dentin) is intended to seal and stabilize the composite/tooth interface, but it degrades leading to a breach at the composite/tooth margin. As the most popular crosslinking monomer in adhesives, Bisphenol A-glycerolate dimethacrylate (BisGMA) has limitations, e.g. susceptible to hydrolysis and concomitant property degradation. A methoxysilyl-functionalized BisGMA derivative (silyl-BisGMA) was introduced in this work to respond to these limitations. Our results indicated that by introducing silyl-BisGMA, higher crosslinked networks were obtained without sacrificing the homogeneity, and the leached amount of HEMA was reduced up to 99%. This novel resin offers potential benefits including prolonging the functional lifetime of dental resin materials.
Asunto(s)
Bisfenol A Glicidil Metacrilato/química , Cementos Dentales/químicaRESUMEN
The most common cause for dental composite failures is secondary caries due to invasive bacterial colonization of the adhesive/dentin (a/d) interface. Innate material weakness often lead to an insufficient seal between the adhesive and dentin. Consequently, bacterial by-products invade the porous a/d interface leading to material degradation and dental caries. Current approaches to achieve antibacterial properties in these materials continue to raise concerns regarding hypersensitivity and antibiotic resistance. Herein, we have developed a multi-faceted, bio-functionalized approach to overcome the vulnerability of such interfaces. An antimicrobial adhesive formulation was designed using a combination of antimicrobial peptide and a ε-polylysine resin system. Effector molecules boasting innate immunity are brought together with a biopolymer offering a two-fold biomimetic design approach. The selection of ε-polylysine was inspired due to its non-toxic nature and common use as food preservative. Biomolecular characterization and functional activity of our engineered dental adhesive formulation were assessed and the combinatorial formulation demonstrated significant antimicrobial activity against Streptococcus mutans. Our antimicrobial peptide-hydrophilic adhesive hybrid system design offers advanced, biofunctional properties at the critical a/d interface.
RESUMEN
Ingress of bacteria and fluids at the interfacial gaps between the restorative composite biomaterial and the tooth structure contribute to recurrent decay and failure of the composite restoration. The inability of the material to increase the pH at the composite/tooth interface facilitates the outgrowth of bacteria. Neutralizing the microenvironment at the tooth/composite interface offers promise for reducing the damage provoked by cariogenic and aciduric bacteria. We address this problem by designing a dental adhesive composed of hybrid network to provide buffering and autonomous strengthening simultaneously. Two amino functional silanes, 2-hydroxy-3-morpholinopropyl (3-(triethoxysilyl)propyl) carbamate and 2-hydroxy-3-morpholinopropyl (3-(trimethoxysilyl)propyl) carbamate were synthesized and used as co-monomers. Combining free radical initiated polymerization (polymethacrylate-based network) and photoacid-induced sol-gel reaction (polysiloxane) results in the hybrid network formation. Resulting formulations were characterized with regard to real-time photo-polymerization, water sorption, leached species, neutralization, and mechanical properties. Results from real-time FTIR spectroscopic studies indicated that ethoxy was less reactive than methoxy substituent. The neutralization results demonstrated that the methoxy-containing adhesives have acute and delayed buffering capabilities. The mechanical properties of synthetic copolymers tested in dry conditions were improved via condensation reaction of the hydrolyzed organosilanes. The leaching from methoxy containing copolymers was significantly reduced. The sol-gel reaction provided a chronic and persistent reaction in wet condition-performance that offers potential for reducing secondary decay and increasing the functional lifetime of dental adhesives. STATEMENT OF SIGNIFICANCE: The interfacial gaps between the restorative composite biomaterial and the tooth structure contributes to recurrent decay and failure of the composite restoration. The inability of the material to increase the pH at the composite/tooth interface facilitates the outgrowth of more cariogenic and aciduric bacteria. This paper reports a novel, synthetic resin that provides buffering capability and autonomous strengthening characteristics. In this work, two amino functional silanes were synthesized and the effect of alkoxy substitutions on the photoacid-induced sol-gel reaction was investigated. We evaluated the neutralization capability (monitoring the pH of lactic acid solution) and the autonomous strengthening property (monitoring the mechanical properties of the hybrid copolymers under wet conditions and quantitatively analyzing the leachable species by HPLC). The novel resin investigated in this study offers the potential benefits of reducing the risk of recurrent decay and prolonging the functional lifetime of dental adhesives.
Asunto(s)
Reactivos de Enlaces Cruzados/química , Cementos Dentales/química , Ensayo de Materiales/métodos , Tampones (Química) , Cromatografía Líquida de Alta Presión , Recubrimiento Dental Adhesivo , Módulo de Elasticidad , Concentración de Iones de Hidrógeno , Cinética , Polimerizacion , Silanos/química , Agua/química , HumectabilidadRESUMEN
OBJECTIVES: The objective of this study was to explore the effect of lysine integration to dental adhesives with respect to the polymerization kinetics, neutralization capacities in the acidic microenvironment, dynamic mechanical properties, and thermal properties. MATERIALS AND METHOD: Lysine was incorporated into liquid resin formulations at 2.5 and 5.0wt % with additional water/ethanol co-solvents. The co-monomer system contained 2-hydroxyethyl-methacrylate (HEMA) and Bisphenol A glycerolate dimethacrylate (BisGMA) with a mass ratio of 45/55. The kinetics of photopolymerization, neutralization capacities, lysine-leaching, dynamic mechanical properties and thermal properties of the control and experimental adhesives were analyzed. RESULTS: The degree of conversion of the experimental adhesive was increased substantially at 2.5wt% lysine as compared to the control. The experimental polymers provided acute neutralization of the acidic microenvironment. Approximately half of the lysine was released from the polymer network within one month. Under dry conditions and physiologic temperatures, the incorporation of lysine did not compromise the storage modulus. Comparison of the thermal properties suggests that the more compact structure of the control adhesive inhibits movement of the polymer chains resulting in increased Tg. SIGNIFICANCE: Incorporating lysine in the adhesive formulations led to promising results regarding modulating pH, which may serve as one aspect of a multi-spectrum approach for enhancing the durability of composite restorations. The results provide insight and lay a foundation for incorporating amino acids or peptides into adhesive formulations for pH modulation or desired bioactivity at the interfacial margin between the composite and tooth.
Asunto(s)
Cementos Dentales/química , Lisina/química , Bisfenol A Glicidil Metacrilato/química , Etanol/química , Concentración de Iones de Hidrógeno , Cinética , Ensayo de Materiales , Metacrilatos/química , Polimerizacion , Polímeros/químicaRESUMEN
OBJECTIVE: To investigate the polymerization kinetics, neutralization behavior, and mechanical properties of amine-functionalized dental adhesive cured in the presence of zwitterionic monomer, methacryloyloxyethyl phosphorylcholine (MPC). METHODS: The control adhesive was a mixture based on HEMA/BisGMA/2-N-morpholinoethyl methacrylate (MEMA) (40/30/30, w/w/w). The control and experimental formulations containing MPC were characterized with regard to water miscibility of liquid resins, photopolymerization kinetics, water sorption and solubility, dynamic mechanical properties and leachables from the polymers (aged in ethanol). The neutralization behavior of the adhesives was determined by monitoring the pH of lactic acid (LA) solution. RESULTS: The water miscibility decreased with increasing MPC amount. The water sorption of experimental copolymer specimen was greater than the control. The addition of 8wt% water led to improved photo-polymerization efficiency for experimental formulations at MPC of 2.5 and 5wt%, and significant reduction in the cumulative amounts of leached HEMA, BisGMA, and MEMA, i.e. 90, 60 and 50% reduction, respectively. The neutralization rate of MPC-containing adhesive was faster than control. The optimal MPC concentration in the formulations was 5wt%. SIGNIFICANCE: Incompatibility between MEMA and MPC led to a decrease in water miscibility of the liquid resins. Water (at 8wt%) in the MPC-containing formulations (2.5-5wt% MPC) led to higher DC, faster RPmax and significant reduction in leached HEMA, BisGMA, and MEMA. The neutralization rate was enhanced with the addition of MPC in the amine-containing formulation. Promoting the neutralization capability of dentin adhesives could play an important role in reducing recurrent decay at the composite/tooth interface.
Asunto(s)
Cementos Dentales , Metacrilatos , Morfolinas , Bisfenol A Glicidil Metacrilato , Ensayo de Materiales , Polimerizacion , AguaRESUMEN
A self-strengthening methacrylate-based dental adhesive system was developed by introducing an epoxy cyclohexyl trimethoxysilane (TS) which contains both epoxy and methoxysilyl functional groups. The experimental formulation, HEMA/BisGMA/TS (22.5/27.5/50, wt%), was polymerized by visible-light. Real-time Fourier transform infrared spectroscopy (FTIR) was used to investigate in situ the free radical polymerization of methacrylate, ring-opening cationic polymerization of epoxy, and photoacid-induced sol-gel reactions. Among the three simultaneous reactions, the reaction rate of the free radical polymerization was the highest and the hydrolysis/condensation rate was the lowest. With 40s-irradiation, the degrees of conversion of the double bond and epoxy groups at 600 s were 73.2±1.2%, 87.9±2.4%, respectively. Hydrolysis of the methoxysilyl group was initially <5%, and increased gradually to about 50% after 48 h dark storage. Photoacids generated through the visible-light-induced reaction were effective in catalyzing both epoxy ring-opening polymerization and methoxysilyl sol-gel reaction. The mechanical properties of copolymers made with TS concentrations from 5 to 35 wt% were obtained using dynamic mechanical analysis (DMA). In wet conditions, the storage moduli at 70 °C and glass transition temperature were significantly higher than that of the control (p<0.05); these properties increased with TS concentration and storage time. The post reaction of hydrolysis/condensation of alkoxysilane could provide persistent strengthening whether in a neutral or acidic environment and these characteristics could lead to enhanced mechanical properties in the oral environment. The cumulative amount of leached species decreased significantly in the TS-containing copolymers. These results provide valuable information for the development of dental adhesives with reduced leaching of methacrylate monomers and enhanced mechanical properties under the wet, oral environment.
RESUMEN
Chemical and enzymatic hydrolysis provoke a cascade of events that undermine methacrylate-based adhesives and the bond formed at the tooth/composite interface. Infiltration of noxious agents, e.g. enzymes, bacteria, and so forth, into the spaces created by the defective bond will ultimately lead to failure of the composite restoration. This paper reports a novel, synthetic resin that provides enhanced hydrolytic stability as a result of intrinsic reinforcement of the polymer network. The behavior of this novel resin, which contains γ-methacryloxyproyl trimethoxysilane (MPS) as its Si-based compound, is reminiscent of self-strengthening properties found in nature. The efforts in this paper are focused on two essential aspects: the visible-light irradiation induced (photoacid-induced) sol-gel reaction and the mechanism leading to intrinsic self-strengthening. The FTIR band at 2840cm(-1) corresponding to CH3 symmetric stretch in -Si-O-CH3 was used to evaluate the sol-gel reaction. Results from the real-time FTIR indicated that the newly developed resin showed a limited sol-gel reaction (<5%) during visible-light irradiation, but after 48h dark storage, the reaction was over 65%. The condensation of methoxysilane mainly occurred under wet conditions. The storage moduli and glass transition temperature of the copolymers increased in wet conditions with the increasing MPS content. The cumulative amounts of leached species decreased significantly when the MPS-containing adhesive was used. The results suggest that the polymethacrylate-based network, which formed first as a result of free radical initiated polymerization, retarded the photoacid-induced sol-gel reaction. The sol-gel reaction provided a persistent, intrinsic reinforcement of the polymer network in both neutral and acidic conditions. This behavior led to enhanced mechanical properties of the dental adhesives under conditions that simulate the wet, oral environment. STATEMENT OF SIGNIFICANCE: A self-strengthening dental adhesive system was developed through a dual curing process, which involves the free radical photopolymerization followed by slow hydrolysis and condensation (photoacid-induced sol-gel reaction) of alkoxylsilane groups. The concept of "living" photoacid-induced sol-gel reaction with visible-light irradiation was confirmed in the polymer. The sol-gel reaction was retarded by the polymethacrylate network, which was generated first; the network extended the life and retained the activity of silanol groups. The self-strengthening behavior was evaluated by monitoring the mechanical properties of the hybrid copolymers under wet conditions. The present research demonstrates the sol-gel reaction in highly crosslinked network as a potentially powerful strategy to prolong the functional lifetime of engineered biomaterials in wet environments.