Inhibitory effects of norcantharidin on titanium particle-induced osteolysis, osteoclast activation and bone resorption via MAPK pathways.

Wear particles generated from the surface of implanted prostheses can lead to peri-implant osteolysis and subsequent aseptic loosening. In the inflammatory environment, extensive formation and activation of osteoclasts are considered the underlying cause of peri-implant osteolysis. Current medications targeting osteoclasts for the treatment of particle-induced bone resorption are not ideal due to significant side effects. Therefore, there is an urgent need to develop more effective drugs with fewer side effects. Norcantharidin (NCTD), a derivative of cantharidin extracted from blister beetles, is currently primarily used for the treatment of solid tumors in clinical settings. However, the potential role of NCTD in treating aseptic loosening of the prosthesis has not been reported. In this study, the in vitro results demonstrated that NCTD could effectively inhibit the formation of osteoclasts and bone resorption induced by the RANKL. Consistently, NCTD strongly inhibited RANKL-induced mRNA and protein levels of c-Fos and NFATc1, concomitant with reduced expression of osteoclast specific genes including TRAP, CTR and CTSK. The in vivo data showed that NCTD exerted significant protective actions against titanium particle-induced inflammation and subsequent osteolysis. The molecular mechanism investigation revealed that NCTD could suppress the activations of RANKL-induced MAPK (p38, ERK). Overall, these findings support the potential use of NCTD for the treatment of aseptic loosening following total joint arthroplasty.

Confirmation of Safety of Titanium Wire in Sternotomy Closure, A Randomized Prospective Study.

BACKGROUND: There are many factors that are known to increase the risk of sternal wound infection (SWI); some studies have reported that nickel is a risk factor for SWI. Titanium wires have only been used as an alternative to steel wires in patients with known allergy to nickel. However, there is a paucity of literature regarding the safety of using titanium wires compared to that on the safety of steel wires for sternum closure after cardiac surgery. Therefore, this study aimed to demonstrate the noninferiority of titanium wires, even in patients without a known allergy. METHODS: A total of 322 patients who underwent elective full median sternotomy were randomly assigned to sternal closure either by titanium wires (n = 161) or by stainless steel wires. RESULTS: Fourteen patients had sternal instability, six (3.7%) patients in the titanium group and eight (5%) patients in the stainless steel group (p = 0.585). There was no statistically significant difference between both groups in terms of postoperative wound infection (p = 0.147). Patients in the titanium group experienced statistically significant lower postoperative pain than those in the stainless steel group (p = 0.024). The wire type was not an independent risk factor for SI, as shown by univariate and logistic regression analyses. CONCLUSION: Titanium wires are a good alternative and have been proven to be safe and effective for sternal closure. The surgeon should be aware of the possibility of developing an allergic reaction to the wires, especially in patients with previous multiple allergic histories.

Risk Factors for Seizures After Titanium Cranioplasty: Five-Year Experience from a Single Institution.

OBJECTIVE: Seizures are one of the complications that can occur after cranioplasty (CP). In some regions, titanium mesh remains the material of choice for CP. However, risk factors for seizures after titanium CP have been less studied. The purpose of this study was to identify potential risk factors for early seizures (≤7 days) and late seizures (>8 days) after titanium CP in a single institution. METHODS: A retrospective review was conducted of 241 consecutive patients who received titanium CP at the First Affiliated Hospital of Harbin Medical University from January 2016 to December 2020. Univariate and multivariable logistic regression analyses were performed to determine the independent risk factors for new-onset seizures after titanium CP. RESULTS: Fifteen patients (6.22%) experienced early post-CP seizures, and late post-CP seizures were observed in 81 patients (33.61%). A flaccid concave cranial defect (P = 0.042) was associated with early post-CP seizures, whereas hypertension (P < 0.001) was the only significant predictor for late seizures after titanium CP. CONCLUSIONS: Seizure is a common complication after titanium CP, especially in patients who do not receive prophylactic antiepileptic drugs before the procedure. Risk factors for new-onset seizures at different periods after titanium CP were found to be different. In addition, radiologic factors before titanium CP may play a role in early new-onset seizures after titanium CP and should not be ignored.

The contribution of metal allergy to the failure of metal alloy implants, with special reference to titanium: Current knowledge and controversies.

After almost three-quarters of a century during which contact dermatologists have often struggled to comprehend the relationship between metal allergy and failure of metal-alloy containing implant, it is possible to say that a relationship does exist, particularly for cobalt and chromium, but also for nickel. There is still debate as to whether allergy develops as a consequent of failure but thenceforth contributes to it, or whether sensitisation starts first and induces failure secondarily-opinion probably favours the first. Metal-on-polypropylene articulations were associated with few metal allergic problems but now are less favoured by orthopaedists due to plastic wear products causing osteolysis and pseudotumour formation through local inflammation. New metal alloys are regularly being introduced such that interested dermatologists need to stay on top of the situation. The jury is still out as to whether the recent favouring of titanium-containing alloys will confirm them to be more inert allergenically. Case reports do show some clinical reactions to titanium-containing implants and patch test series have inferred sometimes quite a high background rate of allergy, but interpretation must be tempered by the awareness that titanium salts on patch testing have a tendency to cause irritant reactions. Blood monitoring of metal ion values is now recommended in certain situations after joint replacement and increasing levels may be an indication that allergy with joint failure can develop, in which case patch testing is indicated, and suggested series are available. Predictive patch testing, whilst generally not recommended in the past, has been introduced into some protocols often by non-dermatologists, such that it is now needed for temporo-mandibular joint and Nuss bar insertion, and it can be anticipated that this may become more commonplace in the future. One of the major current deficits for patch testers is standardised guidance on which preparation or preparations to use for suspected titanium allergy. One suggestion is 0.5% titanium sulphate in petrolatum, though experience in at least one centre suggests the use of a battery of titanium salts might be desirable.

[Effects of metal materials for oral fixation and restoration on magnetic resonance imaging artifacts and the health of tissues around dental implants].

PURPOSE: To investigate the effects of metal materials for oral fixation and restoration on magnetic resonance imaging artifacts and the health of tissues around dental implants. METHODS: A total of 153 patients undergoing fixed oral restoration were selected from May 2018 to June 2020. They were divided according to the random number table method into group A (cobalt-chromium alloy, n=31), group B (nickel-chromium alloy, n=32), group C (titanium alloy, n=28), group D (pure titanium, n=29) and group E (gold alloy, n=33). The largest area of metal crown artifacts and the number of layers of the 5 groups were compared. The probing depth(PD), modified plaque index(mPLI), modified sulcus bleeding index(mSBI) and papilla index(PI) 6 months after restoration were evaluated.The data were statistically analyzed with SPSS 22.0 software package. RESULTS: One-way ANOVA showed that the largest area of metal crown artifacts and the number of layers involved in the 5 groups had significant differences(P＜0.05). Pairwise comparison showed that the largest area of metal crown artifacts, and the number of involved layers in group E were significantly lower than those in groups A, B, C, and D(P＜0.05). One-way ANOVA showed that there was no significant difference in PD, mPLI, mSBI and PI among 5 groups (P＞0.05). Pairwise comparison showed that there was no significant difference in PD, mPLI, mSBI and PI between group A and group B,C,D and E (P＞0.05). CONCLUSIONS: The artifacts produced by metal materials for oral fixation and restoration are closely related to the types of metal materials. Among them, cobalt-chromium alloys produce the largest artifacts, and gold alloys produce the smallest artifacts. The use of metal materials for oral fixation and restoration will not affect the health of tissues around dental implants.

Britanin inhibits titanium wear particle­induced osteolysis and osteoclastogenesis.

Wear particle­induced osteolysis is a serious complication that occurs in individuals with titanium (Ti)­based implants following long­term usage due to loosening of the implants. The control of excessive osteoclast differentiation and inflammation is essential for protecting against wear particle­induced osteolysis. The present study evaluated the effect of britanin, a pseudoguaianolide sesquiterpene isolated from Inula japonica, on osteoclastogenesis in vitro and Ti particle­induced osteolysis in vivo. The effect of britanin was examined in the osteoclastogenesis of mouse bone marrow­derived macrophages (BMMs) using TRAP staining, RT­PCR, western blotting and immunocytochemistry. The protective effect of britanin was examined in a mouse calvarial osteolysis model and evaluated using micro­CT and histomorphometry. Britanin inhibited osteoclast differentiation and F­actin ring formation in the presence of macrophage colony­stimulating factor and receptor activator of nuclear factor kB ligand in BMMs. The expression of osteoclast­specific marker genes, including tartrate­resistant acid phosphatase, cathepsin K, dendritic cell­specific transmembrane protein, matrix metallopeptidase 9 and nuclear factor of activated T­cells cytoplasmic 1, in the BMMs was significantly reduced by britanin. In addition, britanin reduced the expression of B lymphocyte­induced maturation protein­1, which is a transcriptional repressor of negative osteoclastogenesis regulators, including interferon regulatory factor­8 and B­cell lymphoma 6. Conversely, britanin increased the expression levels of anti­oxidative stress genes, namely nuclear factor erythroid­2­related factor 2, NAD(P)H quinone oxidoreductase 1 and heme oxygenase 1 in the BMMs. Furthermore, the administration of britanin significantly reduced osteolysis in a Ti particle­induced calvarial osteolysis mouse model. Based on these findings, it is suggested that britanin may be a potential therapeutic agent for wear particle­induced osteolysis and osteoclast­associated disease.

Full-thickness skin regeneration beneath the exposed titanium mesh in cranioplasty: Two cases report.

RATIONALE: Titanium mesh is one of the most widely used implant materials applied in cranioplasty; however, it has been reported to encounter the risk of progressive scalp thinning and implant exposure over time. Here we present 2 cases of exposed titanium mesh (TM) and unusual phenomena of full-thickness skin regeneration beneath the mesh. PATIENT CONCERNS: Two patients, 1 with an 8-year and 1 with a 2-year history of implant exposure after cranial TM implantation. DIAGNOSES: The patients were diagnosed with scalp ulcers and cranial TM exposure. INTERVENTION: The exposed part of the implant was removed, and the full-thickness skin beneath the mesh was directly used as functional soft tissue coverage to repair the scalp defect. OUTCOMES: Full recovery for both patients with cosmetic satisfaction. LESSONS: Though the exact mechanism of this epithelisation phenomenon beneath the TM remains to be elucidated, it provided a feasible choice for clinicians to reconstruct the scalp's integrity without exerting complicated procedures when dealing with similar cases.

Selenomethionine against titanium particle-induced osteolysis by regulating the ROS-dependent NLRP3 inflammasome activation via the ß-catenin signaling pathway.

Wear debris-induced osteolysis, especially titanium (Ti) particles-induced osteolysis, is the most common cause of arthroplasty failure with no effective therapy. Previous studies have suggested that inflammation and impaired osteogenesis are associated with Ti particles -induced osteolysis. Selenium (Se) is an essential trace element in the human body, which forms selenomethionine (Se-Met) in nature, and selenoproteins has strong anti-inflammatory and antioxidant stress effects. In this study, the effects of Se-Met on Ti particles-induced osteolysis were observed and the potential mechanism was explored. We found that exogenous Se-Met relieved osteolysis induced by Ti particles in two animal models and MC3T3-E1 cells. We found that the addition of Se-Met effectively inhibited Ti particle-induced inflammation by regulating reactive oxygen species-dependent (ROS-dependent) NOD-like receptor protein 3 (NLRP3) inflammasome activation. These therapeutic effects were abrogated in MC3T3-E1 cells that had received a ß-catenin antagonist, suggesting that Se-Met alleviates inflammatory osteolysis via the ß-catenin signaling pathway. Collectively, these findings indicated that Se-Met may serve as a potential therapeutic agent for treating Ti particle-induced osteolysis.

Titanium Particles Modulate Lymphocyte and Macrophage Polarization in Peri-Implant Gingival Tissues.

Titanium dental implants are one of the modalities to replace missing teeth. The release of titanium particles from the implant's surface may modulate the immune cells, resulting in implant failure. However, little is known about the immune microenvironment that plays a role in peri-implant inflammation as a consequence of titanium particles. In this study, the peri-implant gingival tissues were collected from patients with failed implants, successful implants and no implants, and then a whole transcriptome analysis was performed. The gene set enrichment analysis confirmed that macrophage M1/M2 polarization and lymphocyte proliferation were differentially expressed between the study groups. The functional clustering and pathway analysis of the differentially expressed genes between the failed implants and successful implants versus no implants revealed that the immune response pathways were the most common in both comparisons, implying the critical role of infiltrating immune cells in the peri-implant tissues. The H&E and IHC staining confirmed the presence of titanium particles and immune cells in the tissue samples, with an increase in the infiltration of lymphocytes and macrophages in the failed implant samples. The in vitro validation showed a significant increase in the level of IL-1ß, IL-8 and IL-18 expression by macrophages. Our findings showed evidence that titanium particles modulate lymphocyte and macrophage polarization in peri-implant gingival tissues, which can help in the understanding of the imbalance in osteoblast-osteoclast activity and failure of dental implant osseointegration.

STING/TBK1 Regulates Inflammation in Macrophages and Titanium Particles-Induced Osteolysis.

Inflammatory response in macrophages on account of prostheses-derived wear particles is the leading cause of artificial joint failure. However, the mechanism by which wear particles initiate macrophage inflammation has not been fully elucidated. Previous research studies have identified TANK-binding kinase 1 (TBK1) and stimulator of interferon genes (STING) as potential factors in inflammation and autoimmune diseases. Here, we found that both TBK1 and STING were increased in synovium from aseptic loosening (AL) patients and were activated in titanium particles (TiPs)-stimulated macrophages. Lentivirus-mediated knockdown of TBK or STING significantly inhibited the inflammatory effects of macrophages, while overexpression of TBK or STING exerted opposite results. In concrete, STING/TBK1 promoted the activation of NF-κB and IRF3 pathways and macrophage M1 polarization. For further validation, a mice cranial osteolysis model was constructed for in vivo assays, and we found that STING-overexpressed lentivirus injection exacerbated osteolysis and inflammation, which was counteracted by TBK1-knockdown injection. In conclusion, STING/TBK1 enhanced TiP-induced macrophage inflammation and osteolysis via orchestrating the activation of NF-κB and IRF3 pathways and M1 polarization, which suggested STING/TBK1 as potential therapeutic targets for preventing AL of prostheses.

Type IV Titanium Hypersensitivity: Rare, or Rarely Detected?

The presented review aims to summarize the current knowledge of hypersensitivity to titanium - a material widely used in medical applications thanks to its exceptional chemical stability, resistance to corrosion, low specific weight and high strength. The hypersensitivity to metals is usually caused by the Type IV immunopathological reaction. Case reports on allergic reactions to titanium are rare but the actual occurrence can be expected to be much higher, especially due to its problematic detection. Although cutaneous patch tests are widely accepted and used for the diagnosis of hypersensitivity of numerous metals (e.g. Ni), it is notoriously unreliable in case of allergies to titanium, which may be associated with the low percutaneous transport of titanium and its salts. The Lymphocyte Transformation Test has superior sensitivity but it remains mostly unknown among clinicians and there are not many laboratories capable of performing it. This review presents numerous case reports indicating, in combination with the above-mentioned facts, that hypersensitivity to titanium should be considered as a possible cause also in non-specific problems associated with titanium implant failure. Key words: titanium, allergy, patch test, lymphocyte transformation test.

Clinical performance of zirconium implants compared to titanium implants: a systematic review and meta-analysis of randomized controlled trials.

Purpose: To quantitatively assess and compare the clinical outcomes, including survival rate, success rate, and peri-implant indices of titanium and zirconium implants in randomized controlled trials. Methods: The electronic databases searched included the Cochrane Central Register of Controlled Trials (CENTRAL), Medline via Ovid, EMBASE, and Web of Science. Randomized controlled trials (RCTs) that reported the effects of zirconium implants on primary outcomes, such as survival rate, success rate, marginal bone loss (MBL), and probing pocket depth (PPD), compared to titanium implants were included in this review. Two reviewers independently screened and selected the records, assessed their quality, and extracted the data from the included studies. Results: A total of four studies from six publications reviewed were included. Two of the comparative studies were assessed at minimal risk of bias. Zirconium implants may have a lower survival rate (risk ratio (RR) = 0.91, CI [0.82-1.02], P = 0.100, I 2 = 0%) and a significantly lower success rate than titanium implants (RR = 0.87, CI [0.78-0.98], P = 0.030, I 2 = 0%). In addition, there was no difference between the titanium and zirconium implants in terms of MBL, PPD, bleeding on probing (BOP), plaque index (PI), and pink esthetic score (PES) (for MBL, MD = 0.25, CI [0.02-0.49], P = 0.033, I 2 = 0%; for PPD, MD = -0.07, CI [-0.19-0.05], P = 0.250, I 2 = 31%). Conclusion: Zirconium implants may have higher failure rates due to their mechanical weakness. Zirconium implants should be strictly assessed before they enter the market. Further studies are required to confirm these findings.

Titanium dioxide nanoparticles affect osteoblast-derived exosome cargos and impair osteogenic differentiation of human mesenchymal stem cells.

Titanium (Ti) and its alloys are the most widely used metallic biomaterials in total joint replacement; however, increasing evidence supports the degradation of its surface due to corrosion and wear processes releasing debris (ions, and micro and nanoparticles) and contribute to particle-induced osteolysis and implant loosening. Cell-to-cell communication involving several cell types is one of the major biological processes occurring during bone healing and regeneration at the implant-bone interface. In addition to the internal response of cells to the uptake and intracellular localization of wear debris, a red flag is the ability of titanium dioxide nanoparticles (mimicking wear debris) to alter cellular communication with the tissue background, disturbing the balance between osseous tissue integrity and bone regenerative processes. This study aims to understand whether titanium dioxide nanoparticles (TiO2 NPs) alter osteoblast-derived exosome (Exo) biogenesis and whether exosomal protein cargos affect the communication of osteoblasts with human mesenchymal stem/stromal cells (HMSCs). Osteoblasts are derived from mesenchymal stem cells coexisting in the bone microenvironment during development and remodelling. We observed that TiO2 NPs stimulate immature osteoblast- and mature osteoblast-derived Exo secretion that present a distinct proteomic cargo. Functional tests confirmed that Exos derived from both osteoblasts decrease the osteogenic differentiation of HMSCs. These findings are clinically relevant since wear debris alter extracellular communication in the bone periprosthetic niche, contributing to particle-induced osteolysis and consequent prosthetic joint failure.

Silica coated high performance oxide ceramics promote greater ossification than titanium implants: an in vivo study.

BACKGROUND: This in vitro study investigated the osseointegration and implant integration of high performance oxide ceramics (HPOC) compared to titanium implants in rabbits. METHODS: Histomorphometry was conducted around the distal, proximal, medial, and lateral aspects of the HPOC to quantify the amount of mature and immature ossification within the bone interface. Histomorphometry was conducted by a trained musculoskeletal pathologist. The region of interest (ROI) represented the percentage of surrounding area of the implant. The percentage of ROI covered by osteoid implant contact (OIC) and mature bone implant contact (BIC) were assessed. The surrounding presence of bone resorption, necrosis, and/or inflammation were quantitatively investigated. RESULTS: All 34 rabbits survived the 6- and 12-week experimental period. All HPOC implants remained in situ. The mean weight difference from baseline was + 647.7 mg (P < 0.0001). The overall OIC of the ceramic group was greater at 6 weeks compared to the titanium implants (P = 0.003). The other endpoints of interest were similar between the two implants at all follow-up points. No difference was found in BIC at 6- and 12-weeks follow-up. No bone necrosis, resorption, or inflammation were observed. CONCLUSION: HPOC implants demonstrated a greater osteoid implant contact at 6 weeks compared to the titanium implants, with no difference found at 12 weeks. The percentage of bone implant contact of HPOC implants was similar to that promoted by titanium implants.

Indications and complications regarding titanium osteosynthesis in pediatric maxillofacial trauma: A scoping review and critical appraisal.

With the advent of biodegradable osteosynthesis material, titanium osteosynthesis for ORIF in pediatric maxillofacial trauma is not as indisputable as before. The aim of this study was to conduct a scoping review to assess the indications, complications of ORIF with titanium osteosynthesis material in pediatric maxillofacial trauma. A systematic search was conducted in PubMed/MEDLINE, Embase, Web of Science, Cochrane Library, gray literature (ICTRP and clinicaltrials.gov) for studies published until April 2022. 3436 studies were screened and finally 13 articles, compromising a sample of 340 pediatric patients were included after full text reading. Reported complications were infection (6.5% of population), malocclusion (5% of population) and dental maleruption (8% of population). Influence on future growth could not be assessed due to short and heterogeneous follow-up periods. Eight of the thirteen studies concluded to a positive and predictable outcome using titanium ORIF for displaced/complex pediatric maxillofacial fractures. Results of this review suggest that titanium ORIF for maxillofacial fractures in the pediatric population is a reliable treatment. The surgeon must be committed to following these patients longitudinally. Interpreting the results should, however, be done with great care, as most articles have a medium to high risk of bias and limited follow-up.

Suspected allergy to titanium after anterior cervical discectomy and fusion using a Zero-P device: a case report.

PURPOSE: Cases of allergy to large surgical implants have been reported. However, few studies have reported allergy to small titanium-containing implants (e.g. Zero-P device). METHODS: We reported the case of a 51-year old male patient who underwent the anterior cervical discectomy and fusion (ACDF) procedure using a Zero-P device and exhibited allergic symptoms 1 month after the surgery. RESULTS: The allergic symptoms included intermittent tingling and itches in the throat induced by speaking. Systemic rashes over the skin surface and congestion of the eyeball, and dysphagia were also present. Anti-allergic treatment did not resolve the symptoms. Patch tests revealed negative reactions to the rested reagents including titanium. Radiographic results showed solid bone fusion and no signs of chronic inflammation or hypotoxic infection in the surrounding tissues. Upon the patient's request, we removed the titanium screws and plate of the Zero-P device. No allergic reactions were observed after the surgery and at a 6-month follow-up. CONCLUSIONS: Even with a small implant such as the Zero-P device, allergy to titanium may still occur. This case demonstrated the need to screen for the presence of allergy to metals including titanium before the surgery.

Preoperative Metal Patch Testing and Titanium Bar Use Criteria in Nuss Procedure: A 56-Patients' Cohort Study.

INTRODUCTION: Nuss procedure is the main reason for metal implants use by pediatric and thoracic surgeons. There is an ongoing debate on how to avoid allergic complications. Herein we describe our 8-year experience with systematic preoperative metal patch testing and our selective titanium bar use in Nuss procedure. MATERIALS AND METHODS: This is a single center retrospective observational cohort study of patients who underwent the Nuss procedure from 2013 to 2020. Preoperative metal patch testing was done in all cases. Criteria for titanium bar utilization were: a positive test for a major component of the stainless-steel bar; or a positive metal patch test and a positive history of atopy, food or metal allergy, or previous allergic reaction to an implant or device. RESULTS: In total, 56 patients were included. Most were male (91.1%) with a median age of 15.0 (13.0-22.0) years old. 19.6% had a positive preoperative metal patch test and 54.5% of these had no personal history of atopy. Stainless-steel bars were used in 27.3% of those patients and titanium bars were used in 72.7%. One patient had a documented minor allergy reaction. None of the 56 patients required early bar removal. CONCLUSION: Our study suggests that routine preoperative allergy testing and a judicious use of titanium bar are safe and avoid metal allergic complications.

[A non-targeted metabolomics study on serum of occupational people exposed with nanometer titanium dioxide particles (TiO(2)-NPs)].

Objective: To study the changes of serum metabolic profile of occupational people exposed with nanometer titanium dioxide particles (TiO(2)-NPs), and to explore the biomarkers and injury mechanism of TiO(2)-NPs health effects. Methods: From June 2020 to June 2021, a TiO(2)-NPs production enterprise was selected as the research site by a typical sampling method, 64 people in the TiO(2)-NPs exposure group were selected from the enterprise, and 62 people of the logistics administrative staff in the same enterprise were selected as the control group, and blood samples were collected using non-anticoagulant blood collection tubes. After the samples were methanol-precipitated, the untargeted metabolomic data was collected by ultra-high performance liquid chromatography time-of-flight mass spectrometry, and biomarkers were screened and metabolic pathway analysis was performed. Results: 46 different metabolites were screened out by P<0.05 and variable importance projection index (VIP) value >1, mainly including glycerides, sphingomyelin, glycerophospholipid, fatty acyl, etc.; By ROC analysis to determine 3-hydroxy-4, 5-dimethyl-2 (5H) - furanone, 4-aminobiphenyl, heptanoylcarnitine, Hexadecanedioic acid mono-L-carnitine ester, Ibutilide, LysoPA (18∶1 (9Z) /0∶0), LysoPC (18∶0), PC (16∶0/16∶0), PC (16∶0/20: 4 (5Z, 8Z, 11Z, 14Z) ), PC (P-18∶1 (9Z) /P-18∶1 (9Z) ) 10 candidate biomarkers; involving changes in 4 metabolic pathways, namely glycerophospholipid metabolism, sphingolipid metabolism, phenylalanine, tyrosine and tryptophan acid biosynthesis, linoleic acid metabolism. Conclusion: Occupational exposure to TiO(2)-NPs has a significant impact on serum metabolic profiles.