Effects of Solvents and pH Values on the Chemical Affinity of 10-Methacryloyloxydecyl Dihydrogen Phosphate toward Hydroxyapatite

Composite Containing Calcium Phosphate Particles Functionalized with 10-MDP

The phosphate ester monomer 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) is capable of bonding to hydroxyapatite and, for this reason, is a key component of several self-etch adhesives. In this study, dicalcium phosphate dihydrate particles (DCPD; CaHPO4.2H2O) were functionalized with 10-MDP and used to formulate an experimental composite with 50 vol% inorganic content (3:1 DCPD:silanated barium glass ratio) dispersed in a BisGMA/TEGDMA matrix. The tested hypothesis was that DCPD functionalization would improve the composite's mechanical performance without compromising Ca2+ release. Composites containing nonfunctionalized DCPD or only reinforcing glass (in both cases, with or without 10-MDP mixed in the resin phase) were used as controls. Materials were tested for degree of conversion (DC; by Fourier transform infrared spectroscopy), water sorption (WS) and solubility (SL; according to ISO 4049), biaxial flexural strength (BFS)/modulus (FM) after 24 h and 5 mo in water, and 28-d Ca2+ release in water (by plasma-coupled optical emission spectroscopy). Data were analyzed using analysis of variance/Tukey test (alpha: 5%). DCPD functionalization did not interfere with DC. The composite containing functionalized DCPD showed significantly lower WS and SL in comparison with the material formulated with nonfunctionalized particles. The presence of 10-MDP (as a functionalizing agent or dispersed in the resin phase) reduced the composite's initial BFS and FM. After 5 mo in water, the composite with functionalized DCPD and both glass-only composites were able to maintain their mechanical properties at levels statistically similar to what was observed after 24 h. Ca2+ release was significantly reduced in both formulations containing 10-MDP. In conclusion, DCPD functionalization with 10-MDP increased the composite's resistance to hydrolytic degradation, improving its mechanical stability after prolonged water storage. However, the impaired water transit at the particle-matrix interface led to a reduction in Ca2+ release.

Preparation of glucoamylase microcapsule beads and application in solid-state fermentation

BACKGROUND

Baijiu brewing adopts the solid-state fermentation method, using starchy raw materials, Jiuqu as saccharifying fermenting agent, and distilled spirits made by digestion, saccharification, fermentation and distillation. In the late stages of solid-state fermentation of Baijiu, the reduced activity of glucoamylase leads to higher residual starch content in the Jiupei, which affects the liquor yield. The direct addition of exogenous glucoamylase leads to problems such as the temperature of the fermentation environment rising too quickly, seriously affecting the growth of microorganisms.

RESULTS

To solve the problem of reduced activity of glucoamylase in the late stage of solid-state fermentation of Baijiu, microcapsule beads (M-B) based on microcapsule emulsion were prepared and the effect of M-B on solid-state fermentation of Baijiu was investigated. The results showed that the release of M-B before and after drying was 53.27% and 25.77% in the liquid state (120 h) and 29.84% and 22.62% in the solid state (15 days), respectively. Adding M-B improved the alcohol by 0.33 %vol and reducing sugar content by 0.51%, reduced the residual starch content by 1.21% of the Jiupei, and had an insignificant effect on the moisture and acidity of the Jiupei.

CONCLUSION

M-B have excellent sustained-release properties. The addition of M-B in solid-state fermentation significantly increased the alcohol content, reduced the residual starch content of Jiupei, ultimately improving the starch utilization rate and liquor yield of Baijiu brewing. The preparation of M-B provides methods and approaches for applying other active substances and microorganisms in the brewing of Baijiu. © 2023 Society of Chemical Industry.

Role of 3-Methacryloxypropyltrimethoxysilane in Dentin Bonding

In this study, we aimed to examine the effect of 3-methacryloxypropyltrimethoxysilane (MPS) on dentin collagen and the impact of MPS and 10-methacryloyloxydecyl dihydrogen phosphate (MDP) together and separately on resin-dentin bonding. Eight groups of primers were prepared: control group, MDP, MPS5, MPS5 + MDP, MPS10, MPS10 + MDP, MPS15, and MPS15 + MDP. The potential interaction between MPS and collagen was assessed by molecular dynamics, contact angle measurement, zeta potential measurement, and chemoanalytic characterization using X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and ultraviolet-visible spectroscopy. Microtensile bond strength (μTBS) and nanoleakage were evaluated after 24 h or 12 months of water storage. In situ zymography was used to evaluate the enzyme activity at the bonded interface. According to chemoanalytic characterization and molecular dynamics, a weak interaction between MPS and collagen was observed. MPS enhanced the hydrophobicity and negative charge of the collagen surface (P < 0.05). Applying an MDP-containing primer increased μTBS (P > 0.05) and reduced fluorescence after 24 h of water storage. Water storage for 12 months decreased μTBS (P < 0.05) and increased nanoleakage for all groups. MPS conditioning did not change μTBS and nanoleakage after 24 h of water storage or aging. The MPS10 + MDP and MPS15 + MDP groups presented more silver nitrate and μTBS decrease than the MDP group (P < 0.05). These results indicated that MPS had a weak interaction with collagen that enhanced its surface negative charge and hydrophobicity without adversely affecting dentin bonding. However, compared to MDP alone, mixing MDP with MPS impaired their effectiveness and made the dentin bonding unstable.

Interactions of two phosphate ester monomers with hydroxyapatite and collagen fibers and their contributions to dentine bond performance

OBJECTIVES

To evaluate the interactions of two phosphate ester monomers [10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) and dipentaerythritol penta-acrylate phosphate (PENTA)] with hydroxyapatite and collagen and understand their influence on dentine bonding.

METHODS

Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, nuclear magnetic resonance, ultraviolet-visible, and molecular docking were applied for separately evaluating the interactions of two monomers with hydroxyapatite and collagen. Hydrophilicity tests and morphological observation were employed to characterize pretreated dentine. Microtensile bond strength (μTBS) and nanoleakage were investigated to evaluate the bonding performance. Hydroxyproline assay, in situ zymography, and matrix metalloproteinase-9 (MMP-9) activity assay were used to confirm the MMP inhibition.

RESULTS

Chemoanalytic characterization confirmed the interactions of 10-MDP and PENTA with hydroxyapatite and collagen. The interactions of PENTA were weaker than 10-MDP. PENTA possessed better dentine tubule sealing after etching than 10-MDP. Dentine treated with PENTA was more hydrophilic than 10-MDP. 10-MDP and PENTA treating significantly increased the initial μTBS than the control group without primer conditioning. μTBS decreased significantly during aging, and the decrease was more severe in the PENTA group than 10-MDP. The 10-MDP and PENTA groups exhibited relatively less fluorescence than the control. The relative inhibition percentages of MMP-9 decreased in the order of 10-MDP-Ca salt, 10-MDP and PENTA. The 10-MDP, PENTA, and 10-MDP-Ca salt groups showed significantly lower hydroxyproline contents than the control.

CONCLUSIONS

Although PENTA adsorbed on hydroxyapatite, it did not form a stable calcium salt. The interactions of 10-MDP with hydroxyapatite and collagen are different than those of PENTA.

CLINICAL SIGNIFICANCE

The sealing of dentinal tubules by PENTA and the inhibition of MMP by 10-MDP and its calcium salts contribute to improving the dentine bonding durability.

Improved bond performances of self-etch adhesives to enamel through increased MDP-Ca salt formation via phosphoric acid pre-etching

OBJECTIVES

The chemical affinity between 10-methacryloyloxydecyl dihydrogen phosphate (MDP) and hydroxyapatite (HAp) is an important factor in the enamel bonding provided by MDP-based self-etch (SE) adhesives, besides microinterlocking mechanisms. This study aimed to investigate how phosphoric acid pre-etching affects MDP-Ca salt formation in the application of MDP-based SE adhesives.

METHODS

Single Bond Universal (SBU), All Bond Universal (ABU), Clearfil Universal Bond Quick (CBQ), and a MDP-based all-in-one adhesive (EXP) were used in both SE and etch-and-rinse (ER) modes, along with Clearfil SE Bond and untreated enamel (UE) as controls. The MDP-Ca salts produced with or without etching were examined by nuclear magnetic resonance, Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. Zeta potential, contact angle, and scanning electron microscopy measurements were employed to elucidate the mechanism behind the changes in MDP/HAp chemical affinity upon pre-etching.

RESULTS

The percentage of MDP-Ca salt in EXP_ER (73.13%) was higher than that in EXP_SE (43.27%). Characteristic CH₂ (1130, 1441, 2853, and 2909 cm^-1), CC (1641 cm^-1), and CO (1718 cm^-1) bands were observed in the Raman spectra of EXP_ER. Pre-etching increased the negative zeta potential of the enamel surface compared to that of UE (P < 0.001). The contact angles of MDP-based adhesives applied to pre-etched enamel were significantly lower than those of the self-etched surface (P < 0.05).

SIGNIFICANCE

The increased MDP-Ca salt formation is a significant advantage of phosphoric acid pre-etching, improving the MDP/HAp chemical affinity in addition to increasing surface wettability.