Fluoride Ion Release Research Articles

Investigation of Membrane Chemical Degradation as a Function of Catalyst Platinum Loading

Membrane chemical degradation is one of many factors that can impact fuel cell durability. The fuel cell’s lifetime heavily depends on the membrane and its ability to maintain chemical and mechanical integrity. Previous studies indicate that chemical degradation is due to the formation of hydroxyl radicals that attack the polymer structure resulting in membrane thinning, pinhole formation, and the release of fluoride and sulfate ions. Membrane durability was investigated using ultra-low Pt electrode loadings (≤ 0.1 mgPt cm−2). Accelerated stress testing (US-DOE protocols) demonstrated that the degradation rate was found to increase with higher Pt loadings. This is most likely due to more heterogeneous sites for radical formation due to hydrogen crossover to the cathode. We also explored membrane degradation rates while varying catalyst layer thickness, ionomer to carbon ratio, and types of carbon support. All of the aforementioned variables impact the membrane degradation rates.

Remarkable and Unexpected Mechanism for (S)-3-Amino-4-(difluoromethylenyl)cyclohex-1-ene-1-carboxylic Acid as a Selective Inactivator of Human Ornithine Aminotransferase.

Human ornithine aminotransferase (hOAT) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that was recently found to play an important role in the metabolic reprogramming of hepatocellular carcinoma (HCC) via the proline and glutamine metabolic pathways. The selective inhibition of hOAT by compound 10 exhibited potent in vivo antitumor activity. Inspired by the discovery of the aminotransferase inactivator (1S,3S)-3-amino-4-(difluoromethylene)cyclopentane-1-carboxylic acid (5), we rationally designed, synthesized, and evaluated a series of six-membered-ring analogs. Among them, 14 was identified as a new selective hOAT inactivator, which demonstrated a potency 22× greater than that of 10. Three different types of protein mass spectrometry approaches and two crystallographic approaches were employed to identify the structure of hOAT-14 and the formation of a remarkable final adduct (32') in the active site. These spectral studies reveal an enzyme complex heretofore not observed in a PLP-dependent enzyme, which has covalent bonds to two nearby residues. Crystal soaking experiments and molecular dynamics simulations were carried out to identify the structure of the active-site intermediate 27' and elucidate the order of the two covalent bonds that formed, leading to 32'. The initial covalent reaction of the activated warhead occurs with *Thr322 from the second subunit, followed by a subsequent nucleophilic attack by the catalytic residue Lys292. The turnover mechanism of 14 by hOAT was supported by a mass spectrometric analysis of metabolites and fluoride ion release experiments. This novel mechanism for hOAT with 14 will contribute to the further rational design of selective inactivators and an understanding of potential inactivation mechanisms by aminotransferases.

Development and Assessment of New Bioactive Glass Fiber Post. Part II: Ion’s Release

Objectives: This study was designed to develop and assess the ions release property of an innovativeexperimental bioactive fiber-reinforce composite as a new material for an intra-canal post.Study Design: An in vitro studyMaterials and Methods: Surface treated unidirectional E-glass fiber were impregnated and implanted witha triple cure, self-adhesive ACTIVA BioACTIVE resin cement to fabricate an experimental bioactive glassfiber post using hand lay-up moulding technique and polytetrafluoroethylene (PTFE) moulds, The cylindricaland rectangular form specimens were prepared, for each specimen, ensure 3min for self-cure setting, thenlight-cured for the 40s. The specimens were individually immersed in a deionized (DI) water, and sodiumchloride solution to assess the fluoride ion release, and calcium-phosphate ions release sequentially. VirginACTIVA BioACTIVE cement was used as a reference group for all investigations.Statistical analysis used: Statistical analysis was achieved by means of independent variable t-test, onewayANOVA, and Bonferroni Pairwise comparisons utilizing IBM-SPSS software.Results: Experimental material recognized a significant reduction in F-, Ca+2, and PO43- release afterreinforcement compared to virgin ACTIVA BioACTIVE.Conclusions: The ACTIVA BioACTIVE cement’s reinforcement process reduced the ion release intensityof the material but not affected the releasing pattern.

Preliminary In Vitro Study of Fluoride Release from Selected Ormocer Materials.

The purpose of the in vitro study presented in this paper was to determine the long-term release of fluoride ions from selected ormocer materials (Admira (A), Admira Flow (AF), Admira Seal (AS)). The release of fluoride ions from these materials into a saline solution (0.9% NaCl) and deionized water was tested for 14 weeks. In a long-term study the measurements were taken after 1 and 3 h, then 1, 2, and 3 days and then at weekly intervals for 14 weeks. In a short-term study the measurements were made after 3, 24, 48, 72, 69, 168 h, i.e., within 7 days. All materials used in the test showed a constant level of fluoride release. The highest level of cumulative release of fluoride ions into deionized water was found in the AS material (23.95 ± 4.30 μg/mm2), slightly lower in the A material (23.26 ± 4.16 μg/mm2) and the lowest in the AF material (16.79 ± 2.26 μg/mm2). The highest level of cumulative release into saline solution was found in AF (8.08 ± 1.30 μg/mm2), slightly lower in AS (7.36 ± 0.30 μg/mm2) and the lowest in A (6.73 ± 1.10 μg /mm2). After 1 h of immersion of the samples in the saline solution, the highest level of fluoride was released by AF (0.57 ± 0.06 μg/mm2) followed by A (0.20 ± 0.03 μg/mm2) and AS (0.19 ± 0.02 µg/mm2). Moreover, in the 14-week study, the total amount of fluoride release into the saline, which imitates the environment of the oral cavity, was observed as the highest in the AF sample.

Release and Recharge of Fluoride Ions from Acrylic Resin Modified with Bioactive Glass.

Background: Oral hygiene is essential for maintaining residual dentition of partial denture wearers. The dental material should positively affect the oral environment. Fluoride-releasing dental materials help to inhibit microbial colonization and formation of plaque as well as to initiate the remineralization process in the early cavity area. Aim: To evaluate fluoride ion release and recharge capacity, sorption, and solubility of polymethyl methacrylate (PMMA) dental resin modified with bioactive glass addition. Materials and methods: Two bioactive glass materials (5 wt% Kavitan, 10 wt% Kavitan, and 10 wt% Fritex) and pure 10 wt% NaF were added to dental acrylic resin. After polymerization of the modified resins, the release levels of fluoride anions were measured based on color complex formation by using a spectrophotometer after 7, 14, 28, and 35 days of storage in distilled water at 37 °C. Subsequently, specimens were brushed with a fluoride-containing tooth paste on each side for 30 s, and the fluoride recharge and release potential was investigated after 1, 7, and 14 days. Sorption and solubility after 7 days of storage in distilled water was also investigated. Results: The acrylic resins with addition of 10% bioactive glass materials released fluoride ions for over 4 weeks (from 0.14 to 2.27 µg/cm2). The amount of fluoride ions released from the PMMA resin with addition of 10 wt% Fritex glass was higher than that from the resin with addition of 10 wt% Kavitan. The acrylic resin containing 10 wt% NaF released a high amount of ions over a period of 1 week (1.58 µg/cm2), but the amount of released ions decreased rapidly after 14 days of storage. For specimens containing 5 wt% Kavitan glass, the ion-releasing capacity also lasted only for 14 days. Fluoride ion rechargeable properties were observed for the PMMA resin modified with addition of 10 wt% Fritex glass. The ion release levels after recharge ranged from 0.32 to 0.48 µg/cm2. Sorption values ranged from 10.23 μm/mm3 for unmodified PMMA resin to 12.11 μm/mm3 for specimens modified with 10 wt% Kavitan glass. No significant differences were found regarding solubility levels after 7 days. Conclusions: The addition of 10 wt% Fritex and 10 wt% Kavitan bioactive glass materials to heat-cured acrylic resin may improve its material properties, with bioactive fluoride ion release ability lasting for over 4 weeks. The resin modified with 10 wt% Fritex glass could absorb fluoride ions from the toothpaste solution and then effectively release them. Addition of fluoride releasing fillers have a small effect on sorption and solubility increase of the modified PMMA resin. Clinical significance: The addition of bioactive glass may be promising in the development of the novel bioactive heat-cured denture base resin.

Biophysical and Fluoride Release Properties of a Resin Modified Glass Ionomer Cement Enriched with Bioactive Glasses

The aim of this study was to evaluate the bond strength, microleakage, cytotoxicity, cell migration and fluoride ion release over time from a resin-modified glass-ionomer cement (RMGIC) enriched with bioactive glasses (BAGs) and a nanohybrid restorative polymer resin agent used as adhesion material in the cemented brackets. One hundred and twenty bovine lower incisors were divided into three groups: (Transbond Plus Self Etching Primer (TSEP)/Transbond XT (TXT), TSEP/ACTIVA, orthophosphoric acid gel/ACTIVA) and brackets were bonded. A bond strength test and microleakage test were applied. A fluoride release test was applied after 60 days for the TXT and ACTIVA group. To evaluate cytotoxicity and cell migration, a cell viability and scratch migration assay were done for each group. p values < 0.05 were considered significant. Regarding bond strength and microleakage test, no significant differences were found between TSEP/TXT and TSEP/ACTIVA. At 6.4 pH, ACTIVA showed a higher degree of fluoride ion release, which increased with acid pH (3.5), with a maximum fluoride secretion at 30 days. MTT assay revealed that TXT reduces the viability of gingival cells with significant differences (p < 0.001) compared to the untreated cells (control group). ACTIVA provides optimal adhesive and microfiltration properties, releases substantial amounts of fluoride ions in both acid and neutral media, and its biocompatibility is greater than that of traditional composite resin adhesive systems.

Uso do Cimento de Ionômero de Vidro de Alta Viscosidade Como Material Restaurador em Pacientes Portadores da Síndrome de Sjögren: Um Relato de Caso

Objective: this article describes the use of a high viscosity glass ionomer cement as restorative dental treatment in a patient with Sjogren’s syndrome with multiple carious lesions in a university dental clinic in southeastern Brazil. Case Report: a 39-year-old woman, non-smoker, with secondary Sjogren’s syndrome attended an extension clinic called Dental Care for Patients with Chronic Diseases (COPAC) at the School of Dentistry of the Rio de Janeiro State University for dental treatment. The patient was completely dissatisfied with the aesthetics of her smile and was ashamed to show her teeth. During the clinical examination, a large number of carious lesions, defective restorations and missing teeth were observed. Conclusion: although there is no an established protocol for the treatment of carious lesions in patients with Sjogren’s syndrome, restorative treatment with a high viscosity glass ionomer cement (GIC) serves as a favorable option due to fluoride ion release and improved mechanical strength.

Fluoride Ion Release Characteristics of Fluoride-Containing Varnishes—An In Vitro Study

Despite the latest advances in orthodontic treatment, white spot lesions remain a common side effect of fixed appliance therapy. An effective treatment for the prevention of white spot lesions is the use of fluoride-containing products. The aim of the present in vitro study was to check the durability of the tested products for their fluoride release into the surrounding solution. Three varnishes (Protecto CaF2 Nano one-step seal, Bifluorid 12 single dose, and Fluor Protector S) were applied to hydroxyapatite discs and kept in diluted Total Ionic Strength Adjustment Buffer III (TISAB III) solution for fluoride ion release measurement. A group of clear hydroxyapatite discs served as the control group. The carrier discs (N = 40) underwent three thermal cycling runs for 20 days. Before the first run and after each run, the fluoride ion concentration in the solution was measured at appointed times (T) T0, T1, T2, and T3. Fluoride ion release was highest at T1 for all products (median values for Protecto CaF2 Nano one-step seal: 0.09 ppm, Bifluorid 12 single dose: 37.67 ppm, and Fluor Protector S: 3.36 ppm) except for the control group, showing its peak at T0 (0.04 ppm). There was a significant difference between the tested fluoride varnishes at all measurement times. Bifluorid 12 achieved significantly higher fluoride release values than the other products (p < 0.05 at all measurement times). A solitary product application of only once or twice per year, as stated by the manufacturers, cannot be supported.

Marginal Adaptation, Compressive Strength, Water Sorption, Solubility and Ion Release of a Claimed Bioactive Restorative Material

Objectives: This study was conducted to investigate marginal adaptation, compressive strength, water sorption, solubility, fluoride and calcium release of a claimed bioactive restorative material (ACTIVA BioACTIVE Restorative) compared to glass ionomer (Fuji IX) and resin composite (SphereTEC). Materials and methods: ACTIVA was evaluated relative to Fuji IX and SphereTEC one. Marginal gap width was detected via scanning electron microscope before and after thermo-cycling. Compressive strength was tested using universal testing machine. For measuring water sorption and solubility, specimens were immersed in distilled water, subjected to drying cycles and weighed. Fluoride ion release was measured using ion-selective electrode while released calcium ions were detected using Atomic Absorption Spectrophotometer after 1, 14 and 28 days. Data analysis was performed using ANOVA, paired t-test and independent sample t-test. Results: Marginal gap was reduced in both ACTIVA and Fuji IX after thermocycling while it increased in SphereTEC one. After thermo-cycling, the marginal gap was larger in dentin compared to enamel. SphereTEC one showed the highest compressive strength mean value. Fuji IX represented the highest water sorption values, followed by ACTIVA which also exhibited the highest solubility. Fuji IX showed higher fluoride release than ACTIVA whose calcium release did not reach 1ppm. Conclusion: ACTIVA restoration can provide a potential marginal seal. Compressive strength was limited compared to resin composite. ACTIVA’s water sorption and solubility are within the acceptable range. However, its fluoride and calcium release was limited.

Influence on mechanical properties and fluoride ion release when powdery cellulose nanofibers are added to a conventional glass-ionomer restorative

Influence on mechanical properties and fluoride ion release when powdery cellulose nanofibers are added to a conventional glass-ionomer restorative

Peppermint flavor oil in fluoride varnishes enhances fluoride release

Background: Fluoride varnish (FV) is a common dental health treatment for the prevention of early childhood caries. Application of FV with a flavoring agent promotes comfort and acceptance by patients, especially children, and facilitates an effective treatment time. Objective: Flavored FV with a pleasant flavor should allow a faster treatment time, especially with children. The aim of this research was to study basic FV formulations containing different flavors of essential oils (LorAnn) and variations in the concentrations of flavor oils to determine the optimum formulation to enhance the in vitro fluoride release time. Methods: The independent variables were the flavors (apple, melon, and peppermint) and the concentrations (1, 1.5, 2, or 2.5%) of the flavor that gave the best fluoride release (peppermint). The amounts of fluoride ions released in 6 h into deionized water were assessed at 37°C using an ion-selective electrode with the addition of fluoride total ionic strength adjustment buffer solution to strengthen the ion reading. The cumulative ion release was analyzed for normality and equality of variance, and the means were compared using a general linear model test and Statistical Package for Social Sciences version 23.0 software. The significance level was set at α = 0.05. Results: At the same concentration of 2% for the apple, melon, and peppermint flavors, the peppermint formulation gave the best fluoride release, at 173.22 mg/L. A peppermint oil concentration of 2.5% showed the highest fluoride ion release, at 178.95 mg/L. Conclusions: The addition of peppermint flavor oil at a concentration range of 1—2.5% revealed an increasing release of fluoride ions with an increasing peppermint oil concentration. Further investigations are still needed using artificial saliva to replicate actual conditions in the oral cavity.

ACP vs CPP-ACP: The better formula for caries control

Aim: To evaluate and compare the efficacy of two 5% sodium fluoride varnishes containing amorphous calcium phosphate and casein phosphopeptide amorphous calcium phosphate respectively on the plaque pH, salivary fluoride ion release and patient acceptability. Methods: Seventy children were selected from a residential school for the study. Baseline plaque pH, salivary fluoride ion levels were determined. Varnish application was made, and the plaque pH and salivary fluoride ion release were determined at 24 hours, 3 months’ and 6 months’ post varnish application. Patient acceptability was determined immediately after varnish application. Results: No difference in the plaque pH and salivary fluoride ion levels were obtained among the two study groups at all tested time intervals. However, there was a difference in the salivary fluoride ion levels at baseline and at all the three post interventional time periods for both the groups, i.e., at 24 hours (for Group 1 p= 0.00 for Group 2 p=0.00), at 3 months (for Group 1 p=0.00 for Group 2 p=0.00) and at 6 months (for Group 1 p= 0.00 for Group 2 p=0.00). There was no statistically significant difference was observed in the patient acceptability between the two groups (p=0.709). Conclusion: Both the fluoride varnishes can be considered to be equally efficacious when compared based on

(Invited) Liquid Chromatography/Mass Spectrometry Analysis of Effluent Water from Perfluoroalkylsulfonic Acid (PFSA) Membrane Degradation Studies at Accelerated Durability Test Conditions

Perfluorosulfonic acid (PFSA) ionomer membranes degrade under accelerated testing conditions such as open circuit voltage (OCV). Analyzing effluent water for fluoride ion release rate is a primary method for evaluating the membrane degradation rate. However, many proposed degradation reaction pathways should result in the release of small molecule polymer fragments. Liquid chromatography/mass spectrometry (LC/MS) methods are well suited to analyze for these fragments and provide insight into the degradation reactions. Accelerated OCV durability tests were conducted on membrane electrode assemblies made with 3M Ionomer or Nafion™ membranes. Effluent water was analyzed for fluoride, sulfate, and trifluoroacetic acid by ion chromatography (IC) and other polymer fragments by LC/MS. The results of this study imply significant degradation occurs at the tertiary fluoride on the polymer backbone or the ether oxygen connecting the side chain to the backbone. In Nafion™, these structural features also exist in the ionomer sidechain.

Recharge and increase in hardness of GIC with CPP-ACP/F

ObjectiveTo assess the effect of CPP-ACP/F recharging on ion release and hardness of GIC Fuji-Triage (VII) and Fuji-Triage-EP (VII-EP) containing CPP-ACP/F. MethodsCPP-ACP distribution in Fuji-Triage-EP was determined using immunofluorescence. Thirty blocks of Fuji-Triage and Fuji-Triage-EP with the same surface area were placed individually in 5mL of 50mM lactic acid (pH 5) for three days. Every 12h ten Fuji-Triage and ten Fuji-Triage-EP blocks were treated with 2mL of either MI Paste Plus (CPP-ACP/F) solution (1g paste+4mL water), Placebo MI paste solution (no CPP-ACP/F), or distilled water for 2min. After each 2min treatment the blocks were rinsed with distilled water and placed back into the acid. Calcium, inorganic phosphate and fluoride levels in the acid solution were measured using atomic absorption spectrophotometry, colorimetry and ion specific electrode respectively. Vickers surface hardness of the GIC was also determined. Data were analysed using a two-sample t-test and one-way ANOVA with a Bonferroni-Holm correction for multiple comparisons. ResultsCPP-ACP was distributed throughout Fuji-Triage-EP. Significantly (p<0.001) higher calcium, inorganic phosphate and fluoride ion release and greater surface hardness (acid resistance) was observed in both GIC’s treated with the CPP-ACP/F paste. Fuji-Triage-EP released higher ion levels and exhibited greater surface hardness (acid resistance) than Fuji-Triage. SignificanceTopical application of CPP-ACP/F paste to GIC Fuji-Triage-EP recharged ion release and increased surface hardness (acid resistance) which may help improve properties and resistance to degradation as well as improve ion release for caries control.

CHARACTERISTIC OF GLASS IONOMER CEMENT MATERIAL FOR CLINICAL DENTISTRY

Glass ionomer cement (GIC), a thermoplastic polymer, is toughed by ionic bonding is used in dentistry as a filling material. The glass-powder used has some disadvantages such as: poor strength and toughness, and instability in water. Therefore, the aim of this work is to enhance mechanical and fluoride release properties of the GICs by modifying ingredients. The results show that the compressive strength reached to from 60.5 to 86.2 MPa, the setting time met the ISO 9917-1:2007 quality standard. This also suggests that, in addition to 35% PAA in water with Mw of 100,000, 5% of Maleic acid and 5% Tartaric acid to produce GIC which can be used as suitable materials for improving its fluoride ion release over 28 days. The average diameter (dmean) of glass powder for GICs was 14.3 mm; S.P. Surface area was 10,358 cm2=cm3, improvement of liquid composition includes 35% PAA in water with Mw of 100,000, 5% of Maleic acid and 5% Tartaric acid. The compressive strength after curing 28-day reaches from 60.5 to 86.2 MPa and the setting time responds with ISO 9917-1:2007. In conclusion, it was found that the GIC can release fluoride ions (F-) for the during of the examination period.

(Invited) Liquid Chromatography/Mass Spectrometry Analysis of Effluent Water from Perfluoroalkylsulfonic Acid (PFSA) Membrane Degradation Studies at Accelerated Durability Test Conditions

Perfluoroalkylsulfonic acid (PFSA) ionomer membranes degrade under accelerated testing conditions such as open circuit voltage (OCV). Analyzing effluent water for fluoride ion release rate is a primary method for evaluating the membrane degradation rate. However, many proposed degradation reaction pathways should result in the release of small molecule polymer fragments. Liquid chromatography/mass spectrometry (LC/MS) methods are well suited to analyze for these fragments and provide insight into the degradation reactions. Accelerated OCV durability tests were conducted on membrane electrode assemblies made with 3M Ionomer or Nafion™ membranes. Effluent water was analyzed for fluoride, sulfate, and trifluoroacetic acid by ion chromatography (IC) and other polymer fragments by LC/MS. The results of this study imply measurable degradation occurs at the tertiary fluoride on the polymer backbone or the ether oxygen connecting the side chain to the backbone. In Nafion™, these structural features also exist in the ionomer sidechain.

The effect of salbutamol sulfate exposures on the amount of fluoride ion, calcium ion and aluminum ion release from GIC

The effect of salbutamol sulfate exposures on the amount of fluoride ion, calcium ion and aluminum ion release from GIC

Antimicrobial properties, compressive strength and fluoride release capacity of essential oil-modified glass ionomer cements-an in vitro study.

This study was designed to investigate the antimicrobial properties, compressive strength and fluoride release capacities of high-viscous glass ionomer cements (GICs) after incorporation of cinnamon and thyme essential oils. Experimental-modified GICs were prepared by incorporation of thyme and cinnamon essential oils into the liquid phase of the cement at 5 and 10% v/v. Antimicrobial activity against selected microorganisms (Streptococcus mutans and Candida albicans) was done using direct contact test. Compressive strength of the four new formulations and control group was tested using a universal testing machine while fluoride ion release was measured by ion-selective electrode at 1, 7, 14 and 28 days. Data analysis and comparisons between groups were performed using factorial and one-way ANOVA and Tukey's tests. All newly formulated GICs exhibited significantly higher inhibitory effects against both Streptococcus mutans and Candida albicans growth when compared to conventional GIC (p < 0.05). Compressive strength of 5% cinnamon-modified GIC (MPa = 160.32 ± 6.66) showed no significant difference when compared with conventional GIC (MPa = 165.7 ± 5.769) (p value > 0.05). Cumulative fluoride-releasing pattern at days 7, 14, and 28 were 10% cinnamon-GIC > 5% thyme-GIC > 5% cinnamon-GIC > 10% thyme GIC > conventional GIC. Incorporation of 5% cinnamon oil into glass ionomer resulted in better antimicrobial effects against S. mutans and C. albicans and increased fluoride-release capacity without jeopardizing its compressive strength. The 5% cinnamon-modified GIC appears to be a promising alternative restorative material in ART technique.

Photocatalytic transformation fate and toxicity of ciprofloxacin related to dissociation species: Experimental and theoretical evidences

Chemical speciation of ionizable antibiotics greatly affects its photochemical kinetics and mechanisms; however, the mechanistic impact of chemical speciation is not well understood. For the first time, the impact of different dissociation species (cationic, zwitterionic and anionic forms) of ciprofloxacin (CIP) on its photocatalytic transformation fate was systematically studied in a UVA/LED/TiO2 system. The dissociation forms of CIP at different pH affected the photocatalytic degradation kinetics, transformation products (TPs) formation as well as degradation pathways. Zwitterionic form of CIP exhibited the highest degradation rate constant (0.2217 ± 0.0179 min−1), removal efficiency of total organic carbon (TOC) and release of fluoride ion (F−). Time-dependent evolution profiles on TPs revealed that the cationic and anionic forms of CIP mainly underwent piperazine ring dealkylation, while zwitterionic CIP primarily proceeded through defluorination and piperazine ring oxidation. Moreover, density functional theory (DFT) calculation based on Fukui index well interpreted the active sites of different CIP species. Potential energy surface (PES) analysis further elucidated the reaction transition state (TS) evolution and energy barrier (ΔEb) for CIP with different dissociation species after radical attack. This study provides deep insights into degradation mechanisms of emerging organic contaminants in advanced oxidation processes associated to their chemical speciation.

Biomimetic degradability of linear perfluorooctanesulfonate (L-PFOS): Degradation products and pathways

The reductive degradability and decomposition pathways of linear perfluorooctanesulfonate (L-PFOS) were investigated in a biomimetic system consisting of Ti(III)-citrate and Vitamin B12. Biomimetic degradation of L-PFOS could well be described by a first-order exponential decay model. Accompanied by the release of fluoride ion, technical PFOS could not only be transformed to perfluorocarboxylates (PFCAs) and perfluoroalkylsulfonates (PFSAs) with perfluoroalkyl carbon chain length < C8 (thereafter referred as carbon-chain-shortened degradation products), but also be transformed to PFCAs with perfluoroalkyl carbon chain length ≥ C8 (thereafter referred as carbon-chain-lengthened degradation products). Perfluorohexanesulfonate and perfluorotetradecanoate were the most abundant carbon-chain-shortened and -lengthened degradation products of technical PFOS, respectively. Based on the various degradation products detected during biomimetic reduction of linear [1,2,3,4–13C4]-PFOS, the degradation pathways of L-PFOS were proposed as follows: L-PFOS was first reduced to C8F17• radical by cleavage of C–S bond, and then transformed to PFOA through hydrolysis. However, the carbon-chain-shortened products were not generated through the sequential chain-shortening via C8F17• radicals and/or L-PFOS, while the carbon-chain-lengthened products were not formed via C8F17• radicals by stepwise addition of CF2 moiety. In fact, C8F17• radical and/or L-PFOS were further reduced to form CnF2n+1• (n = 1, 2, 3, 4) radicals, and these radicals were chain-lengthened by stepwise addition of C4F8 moiety and eventually transformed to various degradation products via hydrolysis (PFCAs) or combination reaction with sulfonyl hydroxide (PFSAs). All carbon-chain-lengthened chemicals were first reported as the degradation products during the decomposition of L-PFOS, while carbon-chain-shortened compounds were first identified as the biomimetic reduction products of L-PFOS.