Low-fluoride gels supplemented with nano-sized sodium trimetaphosphate reduce dentin erosive wear in vitro

OBJECTIVE

The study assessed the effect of low-fluoride gels supplemented with micrometric or nano-sized sodium trimetaphosphate (TMP) on dentin erosive wear in vitro.

DESIGN

Bovine dentin blocks (n = 154) were selected by surface microhardness and randomly allocated into seven groups (n = 22/group), according to the gels: Placebo; 4500 ppm F (4500F); 9000 ppm F (9000F); 5% TMP microparticulate plus 4500F (5TMPm+4500F); 2.5% TMP nanoparticulate plus 4500 F (2.5TMPn+4500F); 5% TMP nanoparticulate plus 4500F (5TMPn+4500F); and 12,300 ppm F acid gel (APF). All blocks were treated only once for 60 s and cyclically eroded (ERO, citric acid, 4 × 90 s/day) or eroded and brushed (4 × 15 s/day, five strokes/s, ERO+ABR) over five days (each subgroup n = 11). Dentin wear and integrated hardness loss in depth (ΔKHN) were determined, and the data were submitted to two-way ANOVA, followed by Tukey's test, and Spearman's correlation (p < 0.05).

RESULTS

For ERO, all gels containing 4500F supplemented with TMP significantly reduced dentin wear compared with their counterpart without TMP, reaching values similar to 9000F. For ERO+ABR, 5TMPn+ 4500F gel led to significantly lower wear than all its counterparts, reaching values similar to 9000F and APF. As for ΔKHN, all gels containing TMP promoted superior protective effects compared with 4500F, reaching values similar to 9000F and APF under both challenges. A positive correlation between dentin wear and mineral content in depth was verified.

CONCLUSIONS

Gels containing 4500F supplemented with TMP significantly reduced dentin erosive wear compared with pure 4500F, with additional benefit from the use of nanoparticles.

Effect of incorporation of calcium polyphosphate sub-microparticles in low-concentration bleaching gels on physical properties of dental enamel

AIM

To evaluate the bleaching efficacy and effects on enamel properties of experimental gels with carbamide peroxide (CP; 10%) or hydrogen peroxide (HP; 6%) containing calcium polyphosphate sub-microparticles (CaPPs).

METHODS

A total of 216 bovine tooth specimens were divided for microhardness and color analyses (n = 108) and block randomized into nine groups (n = 12): (G1) commercial CP (Whiteness Perfect, FGM; Brazil); (G2) experimental CP; (G3) CP-0.5%CaPPs; (G4) CP-1.5%CaPPs; (G5) commercial HP (Potenza Bianco, PHS; Brazil); (G6) experimental HP; (G7) HP-0.5%CaPPs; (G8) HP-1.5%CaPPs; (G9) artificial saliva. The gels' pH values were determined with a bench pH meter. Color (ΔE, ΔE00, ΔWID) and microhardness variation were evaluated before and after the therapy. Part of the specimens used for microhardness was submitted to the scanning electron microscopy (SEM) (n = 3) and energy-dispersive X-ray spectroscopy EDX (n = 3) analyses. Statistical analyses were performed in the R statistical software (α = 0.05). Linear mixed models for repeated measures in time were used to analyze microhardness and L* values. Generalized linear models were used to analyze the a*, b*, ΔE, ΔE00, and ΔWID, considering a group effect. The EDX data were analyzed using a one-way ANOVA with Tukey's test.

RESULTS

The gels' pH remained over 6,0. All gels effectively bleached the specimens and did not differ significantly. When compared to the control group, the hardness was significantly lower in the G1, G2, G6, and G7 groups. The G3, G4, G5, and G8 groups did not differ significantly (p > 0.05).

CONCLUSION

The incorporation of CaPPs in low-concentration whitening gels reduces its negative effects on microhardness without interfering with their bleaching efficacy.

Fluoride varnishes supplemented with nano-sized sodium trimetaphosphate reduce enamel erosive wear in vitro

OBJECTIVE

To evaluate the effect of fluoride (F) varnishes with sodium trimetaphosphate (TMP) on erosive tooth wear (ETW) in vitro.

METHODS

Enamel blocks (n = 100) were divided into 5 experimental groups (n = 20/group): Placebo (Pla - without F/TMP); 5 % NaF (NaF); 5 % NaF + 5 % micrometric TMP (NaF+5 %MICRO); 5 % NaF + 2.5 % nano-sized TMP (NaF+2.5 %NANO), and 5 % NaF + 5 % nano-sized TMP (NaF+5 %NANO). Blocks received a single varnish application (6 h contact), and were submitted to 4 daily erosive challenges (ERO, 0.05 M citric acid, pH 3.2, 90 s, under agitation), for 5 days. After ERO, half of the blocks (n = 10/group) were subjected to brushing abrasion (ERO+ABR). Profilometry, surface hardness (SH), and cross-sectional hardness (ΔKHN) were determined. The data were submitted to 2-way ANOVA and Fisher's LSD test (p < 0.05).

RESULTS

Enamel wear was significantly lower for ERO compared with ERO+ABR for all varnishes tested (p < 0.001), following the pattern NaF+5 %NANO < NaF+5 %MICRO < NaF < NaF+2.5 %NANO < Pla (both for ERO and ERO+ABR). The highest SH loss was observed for Pla and the lowest for NaF (ERO) and NaF+2.5 %NANO (ERO+ABR), without significant differences among NaF+2.5 %NANO, NaF, and NaF+5 %MICRO. The highest ΔKHN values were observed for NaF+5 %MICRO and NaF+5 %NANO at 5-30 µm, with less marked differences among the groups at 30-70 µm (ERO and ERO+ABR).

CONCLUSIONS

The addition of TMP to F varnishes significantly improves protection against ETW in vitro. The use of 5 % nano-sized TMP further enhances such effects.

CLINICAL SIGNIFICANCE

F varnishes containing TMP can reduce enamel loss caused by ERO or ERO+ABR.

Maintenance of enamel properties after bleaching with high-concentrated hydrogen-peroxide gel containing calcium polyphosphate sub-microparticles

OBJECTIVE

To assessed the physical and chemical properties of human-enamel after treatment with an experimental bleaching gel containing 35%-hydrogen peroxide (HP) and calcium polyphosphate sub-microparticles (CaPP).

MATERIALS AND METHODS

Enamel/dentin specimens (4 × 4 × 3 mm) were obtained (n = 120) and allocated to different groups: control (saliva only); experimental (HP35%); commercial (whiteness-HP-Maxx); CaPP0.5% (HP35% + CaPP0.5wt%); CaPP1.5% (HP35% + CaPP1.5wt%). Three sessions were performed. The specimens' color was assessed using a spectrophotometer and the color (ΔE/ΔE00) and bleaching index (ΔWID) determined. The surface roughness and microhardness were assessed with a roughness tester and Knoop indenter. Raman spectroscopy was performed to obtain the ratios between the areas under the 431, 580, and 1070 cm-1 and the 960 cm-1 bands (430:960, 580:960, 1070:960). Kruskal-Wallis and Dunn compared the color, Ra, and SMH data. The Raman data was analyzed with Kruskal-Wallis and Dunn (α = 5%).

RESULTS

The ΔE, ΔE00, and ΔWID were similar among the bleached groups (p > 0.05). The roughness was not different between the groups (p > 0.05). After the 3rd session, CaPP0.5% had higher microhardness than the experimental (p < 0.05). The 1070:960 was higher in the experimental than in the CaPP1.5% and control (p < 0.05).

CONCLUSIONS

In human enamel, CaPP did not alter the bleaching effectiveness or roughness, and additionally, CaPP-containing gels increased the microhardness and preserved the mineral content when compared to the experimental without CaPP.

CLINICAL RELEVANCE

Experimental bleaching gels containing calcium polyphosphate sub-microparticles as a mineral source reduce the mineral content alteration and superficial microhardness reduction, known potential side effects of the in-office bleaching treatments.

Polyphosphate accumulation and cell-surface properties by autochthonous bacteria from Argentinian Patagonia

Bacteria persisting in environments contaminated with polycyclic aromatic hydrocarbons (PAHs) have developed physiological mechanisms to counteract environmental stress. Inorganic polyphosphate accumulation represents one of these possible mechanisms. Likewise, properties such as cell-surface hydrophobicity, auto-aggregation, biofilm formation and bioemulsifying activity could facilitate interaction of microorganisms with hydrophobic organic compounds. In this work, these physiological properties were compared in indigenous bacteria from polluted sediments from Argentinian Patagonia, which were cultivated in two culture media (LBm and JPP) as a way to improve in the next future the PAHs removal. The highest hydrophobicity values were obtained in Rhodococcus strains, while Bacillus sp. B18 showed the highest auto-aggregation percentage and emulsion index. The highest numerical values of biofilm formation were determined in Rhodococcus sp. F27, Pseudomonas sp. P26, and Gordonia sp. H19 either on hydrophilic or on hydrophobic support. The qualitative and quantitative polyP determinations confirmed the presence of this biopolymer in the strains evaluated. The highest intracellular phosphate mean values were obtained in Bacillus sp. B18 in LBm and Rhodococcus erythropolis 20 in JPP. The bacteria evaluated belonging to different genera showed significant differences in their cell-surface characteristics, bioemulsifying activity and polyP accumulation. The low-cost JPP culture medium was selected for future contaminant removal studies.

Effect of sodium hexametaphosphate and quercetin, associated or not with fluoride, on dentin erosion in vitro

OBJECTIVE

to investigate the ability of solutions containing sodium hexametaphosphate, fluoride and quercetin, alone or in association, to prevent dentin erosion and to inhibit matrix metalloproteinases -2 and -9 activity using in vitro protocols.

DESIGN

Root dentin blocks (n = 96) were prepared and divided into 8 experimental groups (n = 12/group), according to the solutions to be tested: Placebo; 0.24% sodium fluoride (F); 1.0% sodium hexametaphosphate (HMP); 0.03% quercetin (QC); F+HMP; F+QC; HMP+QC; and F+HMP+QC. Erosive challenges were performed 4×/day for 5 days. Specimens were treated with the respective solutions for one minute, twice a day. Next, dentin loss (profilometry) and integrated hardness area in depth (KHN × µm) were determined. The antiproteolytic potential was assessed by gelatin zymography. Dentin erosion results (log₁₀-transformed) were submitted to one-way ANOVA, followed by Tukey's test. Integrated hardness area in depth data (raw) were submitted to two-way, repeated-measures ANOVA, followed by Holm-Sidak's test (p<0.05).

RESULTS

Dentin erosion was significantly lower for F+HMP+QC than for all other treatments. At the shallowest depths (5-30 µm), blocks treated with F+HMP+QC had the highest integrated hardness area in depth values. All treatments completely inhibited matrix metalloproteinases-2 activity, except for the group QC (77% inhibition). For matrix metalloproteinases-9, all HMP-containing solutions or F+QC promoted total antiproteolytic activity.

CONCLUSION

The association of fluoride, sodium hexametaphosphate, and quercetin must be considered a valuable strategy for novel product formulation for home and professional use, considering its superior protective effects against dentin erosion and its antiproteolytic potential.

Silver nanoparticles associated with a polyphosphate and fluoride enhance the prevention of enamel demineralization and impact on dual-biofilm adhesion

OBJECTIVES

The aim of this study were to produce a multifunctional nanocomposite combining silver nanoaparticles (Ag), sodium trimetaphosphate (TMP) and fluoride (F), to investigate its effect on dental enamel demineralization and on biofilms of Streptococcus mutans and Candida albicans.

METHODS

Bovine enamel blocks were submitted to five pH cycles and treated 2x/day with 100ppm F, 225ppm F, 100ppm F+0.2%TMP or 100ppm F+0.2%TMP+10% Ag (100F/TMP/Ag). Next, surface hardness loss (%SH), integrated loss of subsurface hardness (ΔKHN), enamel fluoride (F) and calcium (Ca) concentration were determined. Biofilms from single and dual species of S. mutans and C. albicans were treated with 100F/TMP/Ag, Ag or chlorhexidine gluconate for 24h. The antibiofilm effect was evaluated by colony-forming unit counting and Scanning Electron Microscopy.

RESULTS

The nanocomposite reduced 43.0% of %SH and was similar with samples treated with 225F, 100F/TMP and 100/TMP/Ag. The attribute of F and/or TMP in reducing ΔKHN in 5-20 μm was not affected by the addiction of Ag (110F = 225F = 100F/TMP = 100F/TMP/Ag > Negative Control). Further, 100F/TMP/Ag strongly reduced viable cells of S. mutans in dual biofilms (∼5 log₁₀cm²) and structurally affected the biofilms.

CONCLUSION

The 100F/TMP/F promoted a protective effect against enamel demineralization and was able to significantly inhibit the growth of biofilms of S. mutans and C. albicans.

CLINICAL SIGNIFICANCE

The focus on prevention and non-invasive dental treatment is the most effective and least costly way to improve the population's oral health conditions. We present a nanocomposite for a multiple approach in prevention of caries.

A PKC that controls polyphosphate levels, pinocytosis and exocytosis, regulates stationary phase onset in Dictyostelium

Many cells can pause their growth cycle, a topic much enriched by studies of the stationary phase (SP) of model microorganisms. While several kinases are implicated in SP onset, a possible role for protein kinase C remains unknown. We show that Dictyostelium discoideum cells lacking pkcA entered SP at a reduced cell density, but only in shaking conditions. Precocious SP entry occurs because extracellular polyphosphate (polyP) levels reach a threshold at the lower cell density; adding exopolyphosphatase to pkcA- cells reverses the effect and mimics wild type growth. PkcA's regulation of polyP depended on inositol hexakisphosphate kinase and phospholipase D. PkcA- mutants also had higher actin levels, higher rates of exocytosis and lower pinocytosis rates. Postlysosomes were smaller and present in fewer pkcA- cells, compared to the wildtype. Overall, the results suggest that a reduced PkcA level triggers SP primarily because cells do not acquire or retain nutrients as efficiently, thus mimicking, or amplifying, the conditions of actual starvation.

Polyphosphates as an effective vehicle for delivery of bioavailable nanoparticulate iron(III)

Polyphosphates are widely used food additives with the potential to increase iron bioavailability but chemical nature of their soluble complexes with iron remains largely unknown. Here, pyrophosphate, tripolyphosphate, hexametaphosphate and ∼25-chain-length polyphosphate solubilized 896, 896, 1120 and 1344 mg Fe(III) per g, respectively, at neutral pH by mediating the formation of highly-negatively-charged ferric hydroxide-polyphosphate nanoparticles (PolyP-FeONPs). PolyP-FeONPs displayed fading yellow color with increasing initial dissolved P/Fe ratio ((P/Fe)_init) and decreasing polyphosphate length due to rising proportion of Fe(III)-phosphate bonds, and specifically, pyrophosphate resulted colorless PolyP-FeONPs at (P/Fe)_init ≥ 4. PolyP-FeONPs had weak pro-oxidant activity in glyceryl trilinoleate emulsion and good colloidal stability under spray/freeze-drying and gastrointestinal conditions. Serum iron kinetics in rats revealed sustained iron release and ∼170% iron bioavailability of oral PolyP-FeONPs relative to FeSO₄. Calcein-fluorescence-quenching assay in polarized Caco-2 cells unveiled divalent-metal-transporter-1-independent and macropinocytosis-dependent iron uptake from PolyP-FeONPs. This study helps develop food-compatible, highly-bioavailable and sustained-release iron preparations.

Conversion of soluble recalcitrant phosphorus to recoverable orthophosphate form using UV/H2O2

Soluble non-reactive phosphorus (sNRP), such as inorganic polyphosphates and organic P, is not effectively removed by conventional physicochemical processes. This can impede water resource reclamation facilities' ability to meet stringent total P regulations. This study investigated a UV/H₂O₂ advanced oxidation process (AOP) for converting sNRP to the more readily removable/recoverable soluble reactive P (sRP), or orthophosphate, form. Synthetic water spiked with four sNRP compounds (beta-glycerol phosphate, phytic acid, triphosphate, and hexa-meta phosphate) at varying H₂O₂ concentration, UV fluence, pH, and temperature was initially tested. These compounds represent simple, complex, organic, and inorganic forms of sNRP potentially found in wastewater. The efficiency of sNRP to sRP conversion depended on whether the sNRP compound was organic or inorganic and the complexity of its chemical structure. Using 1 mM H₂O₂ and 0.43 J/cm² (pH 7.5, 22 °C), conversion of the simple organic beta-glycerol phosphate to sRP was 38.1 ± 2.9%, which significantly exceeded the conversion of the other sNRP compounds. Although conversion was achieved, the electrical energy per order (E_EO) was very high at 5.2 × 10³ ± 5.2 × 10² kWh/m³. Actual municipal wastewater secondary effluent, with sNRP accounting for 15% of total P, was also treated using UV/H₂O₂. No wastewater sNRP to sRP conversion was observed, ostensibly due to interference from wastewater constituents. Wastewater utilities that have difficulty meeting stringent P levels might be able to target simple organic sNRP compounds, though alternative processes beyond UV/H₂O₂ need to be explored to overcome interference from wastewater constituents and target more complex organic and inorganic sNRP compounds.

The emerging role of phosphorus in human health

Phosphorus, an essential nutrient, performs vital functions in skeletal and non-skeletal tissues and is pivotal for energy production. The last two decades of research on the physiological importance of phosphorus have provided several novel insights about its dynamic nature as a nutrient performing functions as a phosphate ion. Phosphorous also acts as a signaling molecule and induces complex physiological responses. It is recognized that phosphorus homeostasis is critical for health. The intake of phosphorus by the general population world-wide is almost double the amount required to maintain health. This increase is attributed to the incorporation of phosphate containing food additives in processed foods purchased by consumers. Research findings assessed the impact of excessive phosphorus intake on cells' and organs' responses, and highlighted the potential pathogenic consequences. Research also identified a new class of bioactive phosphates composed of polymers of phosphate molecules varying in chain length. These polymers are involved in metabolic responses including hemostasis, brain and bone health, via complex mechanism(s) with positive or negative health effects, depending on their chain length. It is amazing, that phosphorus, a simple element, is capable of exerting multiple and powerful effects. The role of phosphorus and its polymers in the renal and cardiovascular system as well as on brain health appear to be important and promising future research directions.

Lead accumulation in photosynthetic Euglena gracilis depends on polyphosphates and calcium

Worldwide increasing levels of lead in water systems require the search for efficient ecologically friendly strategies to remove it. Hence, lead accumulation by the free-living algae-like Euglena gracilis and its effects on cellular growth, respiration, photosynthesis, chlorophyll, calcium, and levels of thiol- and phosphate-molecules were analyzed. Photosynthetic cells were able to accumulate 4627 mg lead/kg_DW after 5 days of culture with 200 μM Pb²⁺. Nevertheless, exposure to 50, 100 and 200 μM Pb²⁺ for up to 8 days did not modify growth, viability, chlorophyll content and oxygen consumption/production. Enhanced biosynthesis of thiol molecules and polyphosphates, i.e. the two canonical metal ion chelation mechanisms in E. gracilis, was not induced under such conditions. However, in cells cultured in the absence of phosphate, lead accumulation and polyphosphate content markedly decreased, while culturing in the absence of sulfate did not modify the accumulation of this metal. In turn, the total amount of intracellular calcium slightly increased as the amount of intracellular lead increased, whereas under Ca²⁺ deficiency lead accumulation doubled. Therefore, the results indicated that E. gracilis is highly resistant to lead through mechanisms mediated by polyphosphates and Ca²⁺ and can in fact be classified as a lead hyperaccumulator microorganism.

Amplified morphogenetic and bone forming activity of amorphous versus crystalline calcium phosphate/polyphosphate

Amorphous Ca-phosphate (ACP) particles stabilized by inorganic polyphosphate (polyP) were prepared by co-precipitation of calcium and phosphate in the presence of polyP (15% [w/w]). These hybrid nanoparticles showed no signs of crystallinity according to X-ray diffraction analysis, in contrast to the particles obtained at a lower (5% [w/w]) polyP concentration or to hydroxyapatite. The ACP/15% polyP particles proved to be a suitable matrix for cell growth and attachment and showed pronounced osteoblastic and vasculogenic activity in vitro. They strongly stimulated mineralization of the human osteosarcoma cell line SaOS-2, as well as cell migration/microvascularization, as demonstrated in the scratch assay and the in vitro angiogenesis tube forming assay. The possible involvement of an ATP gradient, generated by polyP during tube formation of human umbilical vein endothelial cells, was confirmed by ATP-depletion experiments. In order to assess the morphogenetic activity of the hybrid particles in vivo, experiments in rabbits using the calvarial bone defect model were performed. The particles were encapsulated in poly(d,l-lactide-co-glycolide) microspheres. In contrast, to crystalline Ca-phosphate (containing only 5% [w/w] polyP) or to crystalline β-tricalcium phosphate, amorphous ACP/15% polyP particles caused pronounced osteoinductive activity already after a six-week healing period. The synthesis of new bone tissue was accompanied by an intense vascularization and an increased expression of mineralization/vascularization marker genes. The data show that amorphous polyP-stabilized ACP, which combines osteoinductive activity with the ability to act as a precursor of hydroxyapatite formation both in vitro and in vivo, is a promising material for bone regeneration.

Porphyromonas gingivalis initiates coagulation and secretes polyphosphates - A mechanism for sustaining chronic inflammation?

BACKGROUND

Periodontitis is a chronic inflammation resulting in destruction of tooth-supporting bone. Chronic inflammation is characterized by extravascular fibrin deposition. Fibrin is central to destruction of bone; monocytes bind to fibrin and form osteoclasts, thus providing a link between coagulation and the tissue destructive processes in periodontitis. The oral microbiome is essential to oral health. However, local ecological changes, such as increased biofilm formation, result in a dysbiotic microbiome characterized by an increase of protease-producing species e.g. Porphyromonas gingivalis. Proteases initiate inflammation and may cleave coagulation factors. Polyphosphates (polyP) may also provide bacteria with procoagulant properties similar to platelet-released polyP. P. gingivalis has also been found in remote locations related to vascular pathology and Alzheimer's disease.

OBJECTIVES

The aim of this study was to investigate procoagulant activity of ten different species of oral bacteria present in oral health and disease as well as presence of polyP and fibrin formation in planktonic and biofilm bacteria.

METHODS

Oral bacteria were studied for protease production and procoagulant activity. The presence of polyP and formation of fibrin was observed using confocal microscopy.

RESULTS

P. gingivalis showed strong protease activity and was the only species exerting procoagulant activity. Confocal microscopy showed polyP intracellularly in planktonic bacteria and extracellularly after biofilm formation. Fibrin formation emanated from planktonic bacteria and from both bacteria and polyP in biofilm cultures.

CONCLUSIONS

The procoagulant activity of P. gingivalis could explain its role in chronic inflammation, locally in oral tissues as well as in remote locations.

Detection of polyphosphates in seafood and its relevance toward food safety

Polyphosphates are permitted as food additives (Regulation EC No 1129/2011) but their undeclared utilisation is considered fraudulent. They improve water holding capacity of the seafood, preventing biochemical/physical changes during commercialization. The key objective of this study was the detection of polyphosphate in various seafood categories, by means of high-performance ion-exchange chromatography with suppressed conductometry (HPIEC-SCD) coupled to Q-Exactive Orbitrap high resolution mass spectrometry (HRMS-Orbitrap). Ten frozen cuttlefish samples did not reveal any treatment, while in ten frigate tunas, high concentration of orthophospate was found. Unambiguous hexametaphosphate presence was demonstrated in four prawn samples, while triphosphate was quantified (11.2 ± 4 ug/g) in another four prawn samples that contained orthophosphate (10225 ± 1102 ug/g), as well. Other samples sporadically encompassed polyphosphates profiles that varied according species and processing type. This analytical approach provided sustenance in better understanding regarding utilization of polyphosphates through HRMS fingerprinting of anionic species that would be specific in food safety control.

Minocycline-loaded calcium polyphosphate glass microspheres as a potential drug-delivery agent for the treatment of periodontitis

Background: Periodontitis is an inflammatory disease with a bacterial etiology that affects the supporting structures of the teeth and is a major cause of tooth loss. The objective of this study was to investigate the drug loading and in vitro release of minocycline from novel calcium polyphosphate microspheres intended for use in treating periodontitis. Methods: Calcium polyphosphate coacervate, produced by a precipitation reaction of calcium chloride and sodium polyphosphate solutions, was loaded with minocycline and subsequently used to produce microspheres by an emulsion/solvent extraction technique. Microspheres classified by size were subjected to a 7-day elution in a Tris-buffer solution under dynamic conditions. The physicochemical characteristics of the drug-loaded microspheres were investigated using scanning electron microscopy, particle size analysis, Phosphorus-31 Nuclear Magnetic Resonance spectroscopy, and Inductively Coupled Plasma Optical Emission Spectroscopy. Drug loading and release were determined using ultraviolet -visible (UV/VIS) spectrophotometry. Results: Minocycline-loaded calcium polyphosphate microspheres of varying size were successfully produced, with small and large microspheres having volume mean diameters of 22 ± 1 µm and 193 ± 5 µm, respectively. Polyphosphate chain length and calcium to phosphorus mole ratio remained stable throughout microsphere production. Drug loading was 1.64 ± 0.16, 1.35 ± 0.55, and 0.84 ± 0.14 weight% for the coacervate and large and small microspheres, respectively, corresponding to mean encapsulation efficiencies of 81.7 ± 12.2 % and 50.9 ± 3.9 % for the large and small microspheres. Sustained drug release was observed in vitro over a clinically relevant 7-day period, with small and large microspheres exhibiting similar elution profiles. Antibiotic release generally followed microsphere degradation as measured by Ca and P ion release. Conclusions: This study demonstrated successful drug loading of calcium polyphosphate microspheres with minocycline. Furthermore, in vitro sustained release of minocycline over a 7-day period was observed, suggesting potential utility of this approach for treating periodontitis.

Investigation on polyphosphate accumulation in the sulfur transformation-centric EBPR (SEBPR) process for treatment of high-temperature saline wastewater

This study investigated the polyphosphates accumulation rate in a novel sulfur transformation-centric enhanced biological phosphorus removal (SEBPR) process. The SEBPR system was continuously operated over 120 days in a sequencing batch reactor (SBR) that alternated between the anaerobic mode and the anoxic mode of operation (temperature: 30 °C and salinity: 6000 mg/L Cl^-). In addition to the SBR, batch experiments were carried out to test the effect of two different sulfate concentrations on the system performance and sulfur-phosphorus transformations. The key intercellular polymers of polyphosphates and polysulfur (poly-S) were identified by employing advanced microscopes. Metagenomic analysis was performed to characterize the diversity of microbes and their functions enriched in the SEBPR system. Finally, several molecular techniques including flow cytometry cell sorting and 16S DNA high-throughput sequencing were applied to identify the phosphorus-accumulating organisms (PAOs). The amounts of P release and P uptake in the SEBPR increased gradually to nearly 18 ± 6.4 mg P/L and 26.5 ± 6.7 mg P/L respectively, yielding a net P removal efficiency of 84 ± 25%. Batch tests indicated no polyhydroxyalkanate (PHA) synthesis, but P uptake was observed and it was correlated with the intracellular poly-S consumption, suggesting that the poly-S could act as an intracellular energy source for P uptake and polyphosphates formation. Moreover, CLSM and TEM micrographs clearly showed the presence of intercellular polyphosphates and poly-S respectively. Metagenomic analysis revealed that Proteobacteria (36.5%), Bacteroidetes (23.3%), Thermotogae (7.1%), Chloroflexi (4.5%) and Firmicutes (2.3%) were the dominant phyla in Bacteria. The conventional PAO of Candidatus Accumulibacter was found at a low abundance of 0.32% only; and an uncultured genus close to Rhodobacteraceae at the family level is speculated to be the putative sulfur PAO (SPAO). Finally, this research suggests that poly-S considerably impacts on polyphosphates accumulation in the SEBPR system when no PHAs are formed.

Antimicrobial Activity of Compounds Containing Silver Nanoparticles and Calcium Glycerophosphate in Combination with Tyrosol

Nanocomposites containing antimicrobial agents and calcium phosphates have been developed. Thus, this study assessed the effects of two compounds containing silver nanoparticles (AgNPs) and β-calcium glycerophosphate (CaGP), associated or not with tyrosol (TYR), against planktonic cells and biofilms of Candida albicans and Streptococcus mutans. The nanocompounds were synthesized through chemical and 'green' processes and characterized by scanning electron microscopy. The minimum and fractional inhibitory concentrations of each compound were determined for planktonic cells. Next, 24-h single biofilms of C. albicans and S. mutans were treated for 24 h with the nanocompounds alone or in combination with TYR, and the antibiofilm effect was assessed through enumeration of colony forming units. Biofilm data were statistically examined using one-way ANOVA and the Kruskal-Wallis test (α = 0.05). The chemically synthesized nanocompound in combination with TYR demonstrated a synergistic effect against planktonic cells of C. albicans and S. mutans. For the nanocompound obtained through the 'green' route associated with TYR, a synergistic effect was observed only against C. albicans. For biofilms, only the combination obtained through the 'green' route + TYR demonstrated a synergistic effect against C. albicans. Our results may contribute to the development of oral care products containing AgNPs-CaGP and TYR to combat oral infections.

Use of solid phosphorus fractionation data to evaluate phosphorus release from waste activated sludge

Waste activated sludge (WAS) can become an important source of phosphorus (P). P speciation was examined under anaerobic conditions, with different pH (4, 6 and 8) and temperatures (10, 20 and 35 °C). Aqueous P was measured and an extraction protocol was used to find three solid phosphorus fractions. A pH of 4 and a temperature of 35 °C gave a maximum of 51% of total P solubilized in 22 days with 50% of total P solubilized in 7 days. Batch tests indicate that little pH depression is needed to release non-apatite inorganic P (including microbial polyphosphate), while a pH of 4 rather than 6 will release more apatite inorganic P, and that organic P is relatively more difficult to release from WAS. Fractionation analysis of P in WAS can aid in design of more efficient methods for P recovery from WAS.

Sodium trimetaphosphate and hexametaphosphate impregnated with silver nanoparticles: characteristics and antimicrobial efficacy

This study aimed to synthesize and characterize materials containing silver nanoparticles (AgNP) with polyphosphates (sodium trimetaphosphate (TMP) or sodium hexametaphosphate (HMP), and evaluate their effect against Candida albicans and Streptococcus mutans. The minimum inhibitory concentration (MIC) was determined, which was followed by the quantification of the biofilm by counting colony-forming units (CFUs), the amount of metabolic activity, and the total biomass. The MICs revealed greater effectiveness of composites containing 10% Ag (TMP + Ag10% (T10) and HMP + Ag10% (H10)) against both microorganisms. It was observed that T10 and H10 reduced the formation of biofilms by 56-76% for C. albicans and by 52-94% for S. mutans for total biomass and metabolic activity. These composites promoted significant log reductions in the number of CFUs, between 0.45-1.43 log₁₀ for C. albicans and 2.88-3.71 log₁₀ for S. mutans (p < .001). These composites demonstrated significant antimicrobial activity, especially against S. mutans, and may be considered a potential alternative for new dental materials.

Nickel accumulation by the green algae-like Euglena gracilis

Nickel accumulation and nickel effects on cellular growth, respiration, photosynthesis, ascorbate peroxidase (APX) activity, and levels of thiols, histidine and phosphate-molecules were determined in Euglena gracilis. Cells incubated with 0.5-1mM NiCl₂ showed impairment of O₂ consumption, photosynthesis, Chl a+b content and APX activity whereas cellular integrity and viability were unaltered. Nickel accumulation was depressed by Mg²⁺ and Cu²⁺, while Ca²⁺, Co²⁺, Mn²⁺ and Zn²⁺ were innocuous. The growth half-inhibitory concentrations for Ni²⁺ in the culture medium supplemented with 2 or 0.2mM Mg²⁺ were 0.43 or 0.03mM Ni²⁺, respectively. Maximal nickel accumulation (1362mg nickel/Kg DW) was achieved in cells exposed to 1mM Ni²⁺ for 24h in the absence of Mg²⁺ and Cu²⁺; accumulated nickel was partially released after 72h. GSH polymers content increased or remained unchanged in cells exposed to 0.05-1mM Ni²⁺; however, GSH, cysteine, γ-glutamylcysteine, and phosphate-molecules all decreased after 72h. Histidine content increased in cells stressed with 0.05 and 0.5mM Ni²⁺ for 24h but not at longer times. It was concluded that E. gracilis can accumulate high nickel levels depending on the external Mg²⁺ and Cu²⁺ concentrations, in a process in which thiols, histidine and phosphate-molecules have a moderate contribution.

pH homeostasis in yeast; the phosphate perspective

Recent research further clarified the molecular mechanisms that link nutrient signaling and pH homeostasis with the regulation of growth and survival of the budding yeast Saccharomyces cerevisiae. The central nutrient signaling kinases PKA, TORC1, and Sch9 are intimately associated to pH homeostasis, presumably allowing them to concert far-reaching phenotypical repercussions of nutritional cues. To exemplify such repercussions, we briefly describe consequences for phosphate uptake and signaling and outline interactions between phosphate homeostasis and the players involved in intra- and extracellular pH control. Inorganic phosphate uptake, its subcellular distribution, and its conversion into polyphosphates are dependent on the proton gradients created over different membranes. Conversely, polyphosphate metabolism appears to contribute in determining the intracellular pH. Additionally, inositol pyrophosphates are emerging as potent determinants of growth potential, in this way providing feedback from phosphate metabolism onto the central nutrient signaling kinases. All these data point towards the importance of phosphate metabolism in the reciprocal regulation of nutrient signaling and pH homeostasis.

Effects of polyphosphates and orthophosphate on the dissolution and transformation of ZnO nanoparticles

The fate and toxicity of zinc oxide nanoparticles (ZnO NPs) in nature are affected by solution chemistry such as pH, anions, and natural organic matter (NOM). Inorganic polyphosphates are environmentally ubiquitous phosphorus (P) species that may change the speciation and environmental fate of ZnO NPs. In this study, the interactions of polyphosphates with ZnO NPs and the impacts on ZnO NP dissolution and transformation were investigated and compared with orthophosphate (P₁). The results revealed that pyrophosphate (P₂), tripolyphosphate (P₃), and hexametaphosphate (P₆) enhanced whereas P₁ inhibited the dissolution of ZnO NPs. In addition, P₁, P₂, and P₃ promoted the transformation of ZnO NPs into zinc phosphate (Zn-P) precipitates via interactions with dissolved Zn²⁺. However, P₆-promoted ZnO NP dissolution was through the formation of soluble Zn-P complexes due to the strong capability of P₆ to chelate with Zn²⁺. The transformation of ZnO NPs in the presence of P₃ was affected by reaction time, pH, and P/Zn molar ratio. P₃ first formed inner-sphere surface complexes on ZnO NPs, which gradually transformed into crystalline Zn₂HP₃O₁₀(H₂O)₆ precipitates. This study provided a new perspective for understanding the reactivity of various forms of inorganic phosphate species with ZnO NPs in the natural environment.

Biochemistry and Physiology of Heavy Metal Resistance and Accumulation in Euglena

Free-living microorganisms may become suitable models for removal of heavy metals from polluted water bodies, sediments, and soils by using and enhancing their metal accumulating abilities. The available research data indicate that protists of the genus Euglena are a highly promising group of microorganisms to be used in bio-remediation of heavy metal-polluted aerobic and anaerobic acidic aquatic environments. This chapter analyzes the variety of biochemical mechanisms evolved in E. gracilis to resist, accumulate and remove heavy metals from the environment, being the most relevant those involving (1) adsorption to the external cell pellicle; (2) intracellular binding by glutathione and glutathione polymers, and their further compartmentalization as heavy metal-complexes into chloroplasts and mitochondria; (3) polyphosphate biosynthesis; and (4) secretion of organic acids. The available data at the transcriptional, kinetic and metabolic levels on these metabolic/cellular processes are herein reviewed and analyzed to provide mechanistic basis for developing genetically engineered Euglena cells that may have a greater removal and accumulating capacity for bioremediation and recycling of heavy metals.

Diadenosine tetra- and pentaphosphates affect contractility and bioelectrical activity in the rat heart via P2 purinergic receptors

Diadenosine polyphosphates (Ap(n)As) are endogenously produced molecules which have been identified in various tissues of mammalian organism, including myocardium. Ap(n)As contribute to the blood clotting and are also widely accepted as regulators of blood vascular tone. Physiological role of Ap(n)As in cardiac muscle has not been completely elucidated. The present study aimed to investigate the effects of diadenosine tetra- (Ap4A) and penta- (Ap5A) polyphosphates on contractile function and action potential (AP) waveform in rat supraventricular and ventricular myocardium. We have also demonstrated the effects of A4pA and Ap5A in myocardial sleeves of pulmonary veins (PVs), which play a crucial role in genesis of atrial fibrillation. APs were recorded with glass microelectrodes in multicellular myocardial preparations. Contractile activity was measured in isolated Langendorff-perfused rat hearts. Both Ap4A and Ap5A significantly reduced contractility of isolated Langendorff-perfused heart and produced significant reduction of AP duration in left and right auricle, interatrial septum, and especially in right ventricular wall myocardium. Ap(n)As also shortened APs in rat pulmonary veins and therefore may be considered as potential proarrhythmic factors. Cardiotropic effects of Ap4A and Ap5A were strongly antagonized by selective blockers of P2 purine receptors suramin and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), while P1 blocker DPCPX was not effective. We conclude that Ap(n)As may be considered as new class of endogenous cardioinhibitory compounds. P2 purine receptors play the central role in mediation of Ap4A and Ap5A inhibitory effects on electrical and contractile activity in different regions of the rat heart.

Effects of polyphosphates and fluoride on hydroxyapatite dissolution: A pH-stat investigation

OBJECTIVES

This study investigated the immediate and sustained effect of sodium trimetaphosphate (TMP) and sodium hexametaphosphate (HMP) associated or not with fluoride (F) on hydroxyapatite (HA) dissolution using an erosion-like model, considering as well as the influence of salivary coating.

DESIGN

Baseline dissolution rates were determined for HA discs using a pH-stat system. In the first set of experiments, HA discs were treated with 1100μgF/mL, 1% or 8% of HMP, 1% or 8% of TMP and 1100μgF/mL associated with 1% or 8% of HMP or TMP, totaling 9 groups (n=8). In a second phase, HA discs were kept in pooled human saliva at 37°C for 2h before treatment with deionised water and 1100μgF/mL associated with 1% or 8% of HMP or TMP, totaling 5 groups (n=8). The post-treatment dissolution rate was determined from three consecutive 30-min assays. Data were analysed using 2 and 3-way ANOVA followed by Fisher and Holm-Sidak methods, respectively (α=0.05).

RESULTS

All test solutions promoted reduction in HA dissolution rate when compared to baseline control in the first post-treatment run (p<0.001). However, a synergistic effect was only observed between fluoride and 1% HMP. Moreover, the duration of inhibitory effect was greater when 8% HMP and 1 or 8% HMP associated with F were assessed (p<0.001). The presence of salivary coating led to higher protection for all groups when compared to discs without coating (p<0.001).

CONCLUSION

The reduction of HA dissolution rate, as well as the duration of this effect were influenced by fluoride, type and concentration of phosphate salt and the presence of a salivary coating.

In situ remineralizing effect of fluoride varnishes containing sodium trimetaphosphate

OBJECTIVE

This study analyzed the effects of a fluoride (F) varnish supplemented with sodium trimetaphosphate (TMP) on the remineralization of caries-like lesions in situ.

MATERIALS AND METHODS

Twelve subjects used palatal devices with demineralized enamel discs for 3 days, following a double-blind, crossover protocol. Test groups included placebo (no F or TMP), 5% NaF and 5% NaF/5% TMP varnishes. The percentage of surface hardness recovery (%SHR) and cross-sectional hardness (ΔKHN) were determined.

RESULTS

Significant differences were observed among all varnishes regarding %SHR and ΔKHN. The highest %SHR and the lowest ΔKHN were seen for the 5% NaF/5% TMP varnish, followed by 5% NaF and placebo.

CONCLUSION

The remineralizing effect of a 5% NaF varnish is significantly enhanced when associated with TMP.

CLINICAL RELEVANCE

The reduction in the subsurface lesion area of enamel treated with the TMP-containing varnish implies that cavities would take longer to develop or might not develop at all depending on individual factors, resulting in lower net caries increments at individual and population levels.

In vitro effect of low-fluoride toothpastes containing sodium trimetaphosphate on enamel erosion

OBJECTIVE

To evaluate the effect of a low-fluoride dentifrice (LFD) containing sodium trimetaphosphate (TMP) on enamel erosion in vitro.

DESIGN

Bovine enamel blocks (n=144) were selected by surface hardness (SH) and subjected to erosive challenges, in two sets of experiments for 2 and 5 days. Blocks were randomly assigned to groups treated with slurries (5mL/block, for 15s) of following dentifrices: Placebo (no fluoride or TMP); LFD (250ppm F); LFD plus 0.25, 0.5, or 1.0% TMP; and a commercial positive control (1,425ppm F). The erosive challenge was produced by immersion in a soft drink (pH 2.8) for 5min, four times/day, interspersed by immersion in artificial saliva for 1h. SH and surface wear were analyzed as response variables. Data were submitted to 2-way ANOVA, followed by Student-Newman-Keuls test (p<0.05).

RESULTS

All groups treated with LFDs containing TMP had significantly lower enamel wear when compared with the other groups tested (p<0.001). Also, the LFDs containing TPM at lower concentrations promoted SH similar to the commercial positive control, both being significantly higher than the LFD without TMP and Placebo (p<0.001).

CONCLUSION

The supplementation of LFDs with TMP is able to significantly increase the anti-erosive potential of these formulations in vitro.

Polyphosphates as inorganic polyelectrolytes interacting with oppositely charged ions, polymers and deposited on surfaces: fundamentals and applications

Polyphosphates are important but neglected polyelectrolytes that play a major role in biology and in surface science for the stabilization of colloids against flocculation and for the preservation of food. They are also known as "Calgon" ® and intensively used as additives in washing powders. This review aims to review recent developments in which linear polyphosphates are used for the design of new functional coatings using sol-gel processes and layer-by-layer deposition methods. All these methods rely on the high charge density of polyphosphates as inorganic polyelectrolytes, therefore the structure and properties of these molecules are also reviewed. New perspectives will also been given for the design of stimuli responsive coatings at the tiny frontier between biology and materials science.

Effect of fluoride gels supplemented with sodium trimetaphosphate on enamel erosion and abrasion: in vitro study

OBJECTIVE

This in vitro study aims to evaluate the effect of low fluoride (F) gel associate sodium trimetaphosphate (TMP) on erosion with or without abrasion.

DESIGN

Enamel blocks (4 mm × 4 mm) selected through surface hardness (SH) is divided into five groups (n=12): gel without F and TMP (placebo), gel containing 4500 ppm F (4500), gel containing 4500 ppm F plus TMP5% (4500 TMP5%), gel containing 9000 ppm F (9000), and gel containing 12,300 ppm F (acid gel). Those groups were additionally subdivided into conditions of erosion (Ero) and of erosion plus abrasion (Ero/Abra). The blocks have undergone a single application of gel on the first day of the study. The erosion challenge was produced by Sprite Zero for five minutes four times a day and abrasion was carried out by machine brushing for 15s. After the challenges, the surface hardness (%SH), wear and cross-sectional hardness (ΔKHN) were analyzed. The data were analyzed using a 2-way ANOVA test followed by a Student-Newman-Keuls (p<0.05).

RESULTS

Lower values of %SH, wear and ΔKHN were observed for erosion challenge (p<0.001). The %SH was lower in groups treated with fluoride gels, differing in the placebo (p<0.05). With addition of TMP to the gel 4500, enamel wear was lower when compared with another groups (p<0.05).

CONCLUSION

In vitro conditions, the 4500 5%TMP gel showed greatest effect against erosion and erosion/abrasion.

Oxygen regulation of alternative respiration in fungus Phycomyces blakesleeanus: connection with phosphate metabolism

Environmental changes can often result in oxygen deficiency which influences cellular energy metabolism, but such effects have been insufficiently studied in fungi. The effects of oxygen deprivation on respiration and phosphate metabolites in Phycomyces blakesleeanus were investigated by oxygen electrode and (31)P NMR spectroscopy. Mycelium was incubated in hypoxic and anoxic conditions for 1.5, 3 and 5 h and then reoxygenated. Participation of alternative oxidase (AOX) in total respiration increased gradually in both treatments and after 5 h of anoxia exceeded a value 50% higher than in control. Shortly after reintroduction of oxygen into the system AOX level decreased close to the control level. Oxygen deprivation also caused a reversible decrease of polyphosphate/inorganic phosphate ratio (PPc/Pi), which was strongly correlated with the increase of AOX participation in total respiration. Unexpectedly, ATP content remained almost constant, probably due to the ability of PolyP to sustain energy and phosphate homeostasis of the cell under stress conditions. This was further substantiated by the effects of azide, a cytochrome c oxidase inhibitor, which also decreased PPc/Pi ratio, but to a smaller extent in oxygen deprived than control and reoxygenated specimens.