Query: pH responsive antibacterial microsphere

title: pH Responsive Antibacterial Resin Adhesives for Secondary Caries Inhibition
abstract: Secondary caries caused by dental plaque is one of the major reasons for the high failure rate of resin composite restoration. Although antimicrobial agent modified dental restoration systems have been researched for years, few reported intelligent anticaries materials could respond to the change of the oral environment and help keep oral eubiosis. Herein, we report tertiary amine (TA) modified resin adhesives (TA@RAs) with pH responsive antibacterial effect to reduce the occurrence of secondary caries. Two kinds of newly designed TA monomers were synthesized: DMAEM (dodecylmethylaminoethyl methacrylate) and HMAEM (hexadecylmethylaminoethyl methacrylate) In the minimum inhibitory concentration and minimum bactericidal concentration test against Streptococcus mutans, Streptococcus sanguinis, and Streptococcus gordonii, they exhibited antibacterial effect only in acidic medium, which preliminarily verified the acid activated effect of TAs. Then DMAEM and HMAEM were incorporated into adhesive resin at the mass fraction of 5% yielding TA@RAs. In vivo and in vitro tests showed that the mechanical properties and biocompatibility of the adhesive were not affected. A S. mutans biofilm model in acidic and neutral medium was used and confirmed that TA@RAs could respond to the critical pH value of de /remineralization and acquire reversible antibiofilm effect via the protonation and deprotonation of TAs. Meanwhile, the stability of antibacterial effect was confirmed via a 5 d pH cycling experiment and a saliva derived biofilm aging model. Furthermore, 16S rRNA gene sequencing showed that TA@RAs could increase the diversity of the saliva derived biofilms, which implied that the novel materials could help regulate the microbial community to a healthy one. Finally, an in vitro demineralization model and in vivo secondary caries model were applied and demonstrated that TA@RAs could prevent secondary dental caries effectively. In summary, the reversible pH responsive and non drug release antibacterial resin adhesives ingeniously overcome the defect of the present materials and hold great promise for clinical application.

title: Antifouling and antibacterial behaviors of capsaicin based pH responsive smart coatings in marine environments.
abstract: Antifouling biocides releasing restricts the longevity of antifouling coatings. Compared with the anchoring state, the releasing behavior of agents is much faster on the voyage, while the biofouling process is tougher. In this work, a series of capsaicin based pH triggered polyethylene glycol/capsaicin@chitosan  polyvinyl alcohol (PVA)/CAP@CS and alginate (ALG)/CAP@CS multilayer films are prepared with controlling antimicrobial properties in marine environments. There are 23.70, 23.35 and 22.06 ppb CAP releasing from (PVA/CAP@CS)20, (PEG/CAP@CS)20 and (ALG/CAP@CS)20 films after immersing in pH 4 solutions for 60 days, while only 13.07, 12.95 and 11.55 ppb CAP have been found in alkaline solutions after immersing for the same time, respectively. All these three types of films exhibit extraordinary pH responsive properties. They can control the CAP release at a low level in alkaline solutions, and make the CAP release fast in acid solutions. Moreover, the antibacterial properties against P.aeruginosa are outstanding about 95.84% 95.0% and 96.91% for (PVA/CAP@CS)20, (PEG/CAP@CS)20 and (ALG/CAP@CS)20 films, respectively. The bacteriostasis of (ALG/CAP@CS)20 film keeps 92.73% after 60 days in alkaline solution, which means it is steadily controlled in the marine environment. Although with similar antibacterial properties to those of (PEG/CAP@CS)20 film, (PVA/CAP@CS)20 film displays the maximum decrease with about 92% in acid solution after 60 days. The ALG/CAP@CS film with the best controlled release performance and long term antibacterial properties provides novel guidance for developing new antifouling coatings application in the marine environment.

title: Intelligent Cellulose Nanofibers with Excellent Biocompatibility Enable Sustained Antibacterial and Drug Release via a pH responsive Mechanism.
abstract: A novel nano sized biomass based pH responsive cellulose nanofibers (CNF PEI) with excellent biocompatibility was tailored by grafting polyethyleneimine (PEI) onto carboxylated cellulose nanofibers (CNF COOH) the active site COOH, 0.96 mmol/g) was anchored on cellulose nanofibers (CNF) to introduce the PEI with a high density (10.57 mmol/g) of amino groups. The as prepared CNF PEI not only maintained the good properties of CNF but also possessed excellent biocompatibility and pH responsive properties, offering interesting perspectives for pH inducing drug sustained release and medical dressing. The CNF PEI showed a rapid wettability conversion from hydrophilic, underwater superoleophobic (WCA=20.7deg, OCA=159.3deg) to hydrophobic, superoleophilic (WCA=129.6deg, ) in response to pH change from acidic conditions to alkaline conditions. The antibacterial properties of CNF PEI for Escherichia coli and Listeria monocytogenes were 100% and 94.6% under acidic conditions, respectively. Furthermore, the pH responsive mechanism of CNF PEI was proposed by XPS, 13C NMR, 1H NMR and AFM analyses.

title: Development of pH Responsive Biopolymeric Nanocapsule for Antibacterial Essential Oils
abstract: It is generally believed that antibacterial essential oils have the potential to become one of the alternatives in preventing diarrheal diseases of monogastric animals. The disadvantage is their low efficiency per oral due to easy degradation during digestion in the stomach. This study compares the efficacy of chitosan, alginate chitosan, guar gum chitosan, xanthan gum chitosan and pectin chitosan nanocapsules to the synthesis of pH responsive biopolymeric nanocapsule for Thymus vulgaris, Rosmarinus officinalis and Syzygium aromaticum essential oils. Using spectrophotometric approach and gas chromatography, release kinetics were determined in pH 3, 5.6 and 7.4. The growth rates of S. aureus and E. coli, as well as minimal inhibition concentration of essential oils were studied. The average encapsulation efficiency was 60% and the loading efficiency was 70% The size of the nanocapsules ranged from 100 nm to 500 nm. Results showed that chitosan guar gum and chitosan pectin nanocapsules released 30% of essential oils (EOs) at pH 3 and 80% at pH 7.4 during 3 h. Similar release kinetics were confirmed for thymol, eugenol and a pinene. Minimal inhibition concentrations of Thymus vulgaris and Syzygium aromaticum essential oils ranged from 0.025 to 0.5% Findings of this study suggest that the suitable pH responsive nanocapsule for release, low toxicity and antibacterial activity is based on chitosan guar gum structure.

title: Antibacterial and pH responsive Quaternized Hydroxypropyl Cellulose g Poly(THF co epichlorohydrin) Graft Copolymer: Synthesis, Characterization and Properties
abstract: The novel quaternized hydroxypropyl cellulose g poly(THF co epichlorohydrin) graft copolymers, HPC g QCP(THF co ECH) have been successfully synthesized to combine the properties from hydrophilic hard HPC biomacromolecular backbone and hydrophobic flexible polyether branches. Firstly, the P(THF co ECH) living chains were synthesized by cationic ring opening copolymerization of THF with ECH. Secondly, P(THF co ECH) living chains were grafted onto HPC backbone by reaction with OH groups along HPC to produce HPC g P(THF co ECH) graft copolymers. Thirdly, the mentioned graft copolymers were quaternized by reaction with ternary amine to generate functionalized HPC g QCP(THF co ECH) The HPC g QCP(THF co ECH) graft copolymers exhibited good antibacterial ability against S. aureus or E. coli bacteria. The ibuprofen (IBU) loaded microparticles of HPC g (QC)P(THF co ECH) graft copolymers were prepared by electrospraying. The in vitro pH responsive drug release behavior of IBU reached up to 75% of drug loaded at pH 7.4. This quaternized graft copolymer was beneficial to solving the problems of a burst effect and fast release of HPC as drug carriers.

title: Chelating ZnO dopamine on the surface of graphene oxide and its application as pH responsive and antibacterial nanohybrid delivery agent for doxorubicin.
abstract: In this work, a new pH responsive nanohybrid carrier was prepared with chelating ZnO dopamine (Zn d) on the surface of graphene oxide. Doxorubicin (DOX) as a model drug was loaded on the resulted nanohybrid. The characteristics of Zn d rGO nanohybrid (NH) determined using Fourier transformed infrared spectroscopy (FT IR) X ray Diffraction spectroscopy (XRD) UV Visible spectroscopy, Scanning Electron Microscope (SEM) EDX and AFM. The BET analysis showed a specific surface area of 37.16 m2/g and the obtained nanohybrid indicated a high loading capacity of DOX up to 99.7% and the release profile displayed a pH dependent discharge in the acidic environment for14 days. The cytotoxicity of the prepared nanohybrid was measured against T47D and MCF10A cells and it confirmed that as prepared nanohybrid has high toxicity against cancer cells and lower effect against human breast cell. Meanwhile, the prepared nanohybrids showed well antimicrobial activity against gram positive and negative bacteria. The obtained results showed that the prepared nanohybrid (Zn d rGO) could potentially be used as a safe carrier for drug delivery systems.

title: pH Responsive Self Healing Anticorrosion Coating Based on a Lignin Microsphere Encapsulating Inhibitor
abstract: In this work, we offered a facile strategy to produce lignin microspheres (LMS) with loading of benzotriazole (BTA) inhibitors, which were released as the pH changed. The morphological and composit.

title: pH responsive Calcium and Phosphate Ion Releasing antibacterial Sealants on Carious Enamel lesions in vitro.
abstract: Nanoparticles of amorphous calcium phosphate (NACP) have shown beneficial effects of a robust release of calcium and phosphate ions at low pH. Here we examined the effect of NACP combined into antibacterial/rechargeable sealant formulations on the mineral content of artificial carious enamel during pH cycling mimicking intraoral conditions.  NACP and a quaternary ammonium methacrylate (DMAHDM) were synthesized. Three resin sealants were formulated: "base formulation" (without NACP and DMAHDM, used as control) "NACP on the base formulation" (with 20 wt. NACP) "NACP on the antibacterial formulation" (with 20 wt. NACP and 5 wt. DMAHDM) Standardized enamel windows on sealed non carious human molars were demineralized and randomly divided into four groups: three groups of teeth sealed with the experimental materials and one group of teeth without sealant application used as negative control. The teeth were exposed to pH cycling regime. The changes in the mineral content of enamel were assessed by quantitative surface hardness loss in percentage %SHL) and qualitative analyses via scanning electron microscopy/energy dispersive X ray spectroscopy (SEM EDX) and polarized light microscopy (PLM)  The contact with NACP containing formulations provoked significant lower %SHL on sealed enamel (p 0.05) in comparison to control groups. This outcome was supported by the results of SEM EDX, in which the enamel presented higher percentages of calcium and phosphate than control groups. PLM showed less enamel superficial demineralization around the sealants containing NACP.  NACP incorporated into an antibacterial sealant protected the enamel against demineralization. pH responsive calcium and phosphate ion releasing sealants with antimicrobial and rechargeable properties may be a reliable complementary approach for caries management.  Dental caries is the most common childhood disease. Enamel demineralization represents the initial stage of carious lesion formation and may lead to invasive dental procedures. We explored the role of amorphous calcium phosphate (NACP) in a newly developed antibacterial and rechargeable dental sealant formulation as a preventive approach.

title: Thermosensitive and pH responsive tannin containing hydroxypropyl chitin hydrogel with long lasting antibacterial activity for wound healing.
abstract: Polysaccharide hydrogels have been widely used as wound dressings because of their biocompatibility and ability to provide moist environment for wound healing. However, bacterial infection often delays the healing process. Herein, a novel thermosensitive and pH sensitive hydroxypropyl chitin/tannic acid/ferric ion (HPCH/TA/Fe) composite hydrogel was fabricated by a simple assembly. The pre cooled hydrogel precursor solution can be injected onto the irregular wound area and gel rapidly at physiological temperature. The TA not only acted as a crosslinker to enhance mechanical properties of the hydrogel, but also as an antibacterial agent which could be sustainably released in response to the acidic environment. The composite hydrogel showed excellent broad spectrum antibacterial activity up to 7 days with negligible cytotoxicity. Moreover, the hydrogel can inhibit bacterial infection and accelerate the wound healing process without scars in the mouse experiment. These results indicate the potential application of this composite hydrogel for the infected wound healing.

title: pH responsive silk fibroin based CuO/Ag micro/nano coating endows polyetheretherketone with synergistic antibacterial ability, osteogenesis, and angiogenesis.
abstract: Polyetheretherketone has been widely used for bone defect repair, whereas failures may happen due to implant loosening and infection. Thus, PEEK implant with multi function (osteogenesis, angiogenesis, and bacteria killing) is essential to solve this problem. Herein, copper oxide microspheres (mCuO) decorated with silver nanoparticles (nAg) were constructed on porous PEEK surface via silk fibroin. In vitro studies highlighted the pH controlled release ability of this coating. It liberated a high dose of Cu2+ and Ag+ at low pH environment (pH 5.0) leading to 99.99% killing of planktonic bacteria and complete eradication of sessile bacteria, avoiding biofilm formation. Under physiological environment (pH 7.4) a lower amount of leaked metal ions induced promoted ALP production, collagen secretion, and calcium deposition, as well as NO production, which indicated potentiated osteogenesis and angiogenesis. In vivo results displayed the highest new bone volume around, and the appearance of new bone inside porous structure of, PEEK implant with this coating in rabbit tibia, signified the abilities of this coating to promote bone regeneration and osseointegration. Our study established solid support for implants with this coating to be a successful bone defect repair solution.