Role of Recurrence Pattern Multiplicity in Predicting Post-recurrence Survival in Patients Who Underwent Curative Gastrectomy for Gastric Cancer.

PURPOSE: This study aimed to investigate the recurrence patterns in patients who underwent curative surgery for gastric cancer (GC) and analyze their prognostic value for post-recurrence survival (PRS). MATERIALS AND METHODS: We retrospectively reviewed the medical records of 204 patients who experienced GC recurrence following curative gastrectomy for GC at a single institution between January 2012 and December 2017. Specific recurrence patterns (lymph node, peritoneal, and hematogenous) and their multiplicity were analyzed as prognostic factors of PRS. RESULTS: The median PRS of the 204 patients was 8.3 months (interquartile range [IQR]: 3.2-17.4). For patients with a single recurrence pattern (n=164), the difference in each recurrence pattern did not show a significant prognostic value for PRS (lymph node vs. peritoneal, P=0.343; peritoneal vs. hematogenous, P=0.660; lymph node vs. hematogenous, P=0.822). However, the patients with a single recurrence pattern had significantly longer PRS than those with multiple recurrence patterns (median PRS: 10.2 months [IQR: 3.7-18.7] vs. 3.9 months [IQR: 1.8-10.4]; P=0.037). In the multivariate analysis, multiple recurrence patterns emerged as independent prognostic factors for poor PRS (hazard ratio, 1.553; 95% confidence interval, 1.092-2.208; P=0.014) along with serosal invasion, recurrence within 1 year after gastrectomy, and the absence of post-recurrence chemotherapy. CONCLUSIONS: Regardless of the specific recurrence pattern, multiple recurrence patterns emerged as independent prognostic factors for poor PRS compared with a single recurrence pattern.

Genotoxicity assessment of root extracts of Paeonia lactiflora Pall.

The roots of Paeonia lactiflora Pall., (Paeoniae Radix, PL) are a well-known herbal remedy used to treat fever, rheumatoid arthritis, systemic lupus erythematosus, hepatitis, and gynecological disorders in East Asia. Here we evaluated the genetic toxicity of PL extracts (as a powder [PL-P] and hot-water extract [PL-W]) in accordance with the Organization for Economic Co-operation and Development guidelines. The Ames test revealed that PL-W was not toxic to S. typhimurium strains and E. coli in absence and presence of the S9 metabolic activation system at concentrations up to 5000 µg/plate, but PL-P produced a mutagenic response to TA100 in the absence of S9 mix. PL-P was cytotoxic in in vitro chromosomal aberrations (more than a 50 % decrease in cell population doubling time), and it increased the frequency of structural and numerical aberrations in absence and presence of S9 mix in a concentration-dependent manner. PL-W was cytotoxic in the in vitro chromosomal aberration tests (more than a 50 % decrease in cell population doubling time) only in the absence of S9 mix, and it induced structural aberrations only in the presence of S9 mix. PL-P and PL-W did not produce toxic response during the in vivo micronucleus test after oral administration to ICR mice and did not induce positive results in the in vivo Pig-a gene mutation and comet assays after oral administration to SD rats. Although PL-P showed genotoxic in two in vitro tests, the results from physiologically relevant in vivo Pig-a gene mutation and comet assays illustrated that PL-P and PL-W does not cause genotoxic effects in rodents.

Prx1 Regulates Thapsigargin-Mediated UPR Activation and Apoptosis.

Endoplasmic reticulum (ER) stress activates the unfolded protein response (UPR) signaling via the accumulation of unfolded and misfolded proteins. ER stress leads to the production of reactive oxygen species (ROS), which are necessary to maintain redox homeostasis in the ER. Although peroxiredoxin 1 (Prx1) is an antioxidant enzyme that regulates intracellular ROS levels, the link between Prx1 and ER stress remains unclear. In this study, we investigated the role of Prx1 in X-box binding protein 1 (XBP-1) activation, the C/EBP homologous protein (CHOP) pathway, and apoptosis in response to ER stress. We observed that Prx1 overexpression inhibited the nuclear localization of XBP-1 and the expression of XBP-1 target genes and CHOP after thapsigargin (Tg) treatment to induce ER stress. In addition, Prx1 inhibited apoptosis and ROS production during ER stress. The ROS scavenger inhibited ER stress-induced apoptosis but did not affect XBP-1 activation and CHOP expression. Therefore, the biological role of Prx1 in ER stress may have important implications for ER stress-related diseases.

Comparative sub-chronic toxicity studies in rats of two indistinguishable herbal plants, Cynanchum wilfordii (Maxim.) Hemsley and Cynanchum auriculatum Royle ex Wight.

Sub-chronic toxicity studies using rats have been conducted for Cynanchum wilfordii (Maxim.) Hemsley (CW) and Cynanchum auriculatum Royle ex Wight (CA). CW water extract didn't show any adverse effects whereas administering CW powder decreased body weights in complication with decreased food consumptions. In the case of CA water extract, triglyceride and absolute/relative liver weights were elevated and vacuolation was observed in liver. Treated CA powder in male rats increased alanine aminotransferase and aspartate aminotransferase and induced single cell necrosis and multinucleated hepatocyte in liver. As for female rats, increased absolute/relative weights and hypertrophy/vacuolation in adrenal glands and vacuolation in ovaries were observed when administered CA powder. In conclusion, no observed adverse effect level (NOAEL) of CW water extract was over 5000 mg/kg/day, while NOAEL of CW powder was 700 mg/kg/day for female and 150 mg/kg/day for male. In case of CA, NOAEL of water extract was 1500 mg/kg/day for male and 2000 mg/kg/day for female, while NOAEL of powder was 150 mg/kg/day for both gender. To the best of our knowledge, this is the first sub-chronic toxicity study on the adverse effects, target organs and its dose levels of C. wilfordii (Maxim.) Hemsley and C. auriculatum Royle ex Wight following GLP protocols.

Colony-Forming Efficiency Assay to Assess Nanotoxicity of Graphene Nanomaterials.

The nano-market has grown rapidly over the past decades and a wide variety of products are now being manufactured, including those for biomedical applications. Despite the widespread use of nanomaterials in various industries, safety and health effects on humans are still controversial, and testing methods for nanotoxicity have not yet been clearly established. Nanomaterials have been reported to interfere with conventional cytotoxicity tests due to their unique properties, such as light absorption or light scattering. In this regard, the colony-forming efficacy (CFE) assay has been suggested as a suitable test method for testing some nanomaterials without these color-interferences. In this study, we selected two types of GNPs (Graphene nanoplatelets) as test nanomaterials and evaluated CFE assay to assess the cytotoxicity of GNPs. Moreover, for further investigation, including expansion into other cell types, GNPs were evaluated by the conventional cytotoxicity tests including the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS), Cell Counting Kit-8 (CCK-8), and Neutral red uptake (NRU) assay using MDCK, A549 and HepG2 cells. The results of CFE assay suggest that this test method for three cell lines can be applied for GNPs. In addition, the CFE assay was able to evaluate cytotoxicity regardless more accurately of color interference caused by residual nanomaterials.

Sustainable Antibacterial and Antiviral High-Performance Copper-Coated Filter Produced via Ion Beam Treatment.

With the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), disease prevention has become incredibly important. Consequently, mask and air-purifier use has increased. The filter is the core component of these items. However, most filter materials lack antimicrobial properties. Copper is a sustainable antimicrobial material. When copper is deposited onto the filter's surface, the microorganisms that come into contact with it can be effectively inactivated. In this study, we used an oxygen ion beam with a controlled process temperature to treat filter surfaces with copper. This enabled a strong adhesion of at least 4 N/cm between the copper and the filter fibers without damaging them. Upon exposing the filter to bacteria (Staphylococcus aureus ATCC 6538, Klebsiella pneumoniae ATCC 4352, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa ATCC 27853) for one hour, a >99.99% removal rate was attained; when the filter was exposed to SARS-CoV-2 virus for one hour, it inactivated more than 99%. These beneficial properties minimize the risk of secondary infections, which are significantly more likely to occur when a conventional filter is replaced or removed.

Efficacy and Safety of Trastuzumab Biosimilar (CT-P6) Compared With Reference Trastuzumab in Patients With HER2-positive Advanced Gastric Cancer: A Retrospective Analysis.

OBJECTIVES: Treatment with trastuzumab and chemotherapy significantly improves the outcome in patients with human epidermal growth factor receptor 2 (HER2)-positive advanced gastric cancer (AGC). CT-P6 (trastuzumab-pkrb; Herzuma) is a trastuzumab biosimilar approved for the treatment of HER2-positive gastric cancer. In this study, we aimed to compare the efficacy and safety of CT-P6 and reference trastuzumab as first-line treatment for HER2-positive AGC. MATERIALS AND METHODS: The medical records of 102 patients with HER2-positive AGC treated with first-line trastuzumab-based chemotherapy were retrospectively reviewed. These patients were treated with either reference trastuzumab (n=72) or a biosimilar (n=30). Treatment outcomes, such as objective response rate, progression-free survival (PFS), and overall survival (OS), were compared between the reference and biosimilar groups. RESULTS: The objective response rate of both groups (52.8% and 56.8% in the reference and biosimilar groups, respectively) were comparable (P=0.72). No statistically significant difference was observed with the reference versus biosimilar trastuzumab for PFS (median PFS, 6.9 vs. 5.4 mo; P=0.98) or OS (median OS, 12.3 mo vs. not reached; P=0.42). Safety profiles were similar between the 2 groups. CONCLUSIONS: Biosimilar trastuzumab showed equivalent outcome to reference trastuzumab, with similar adverse events. Biosimilar trastuzumab can suitably and safely replace trastuzumab as a reference for the treatment of HER2-positive AGC.

Prevention of Breast Implant Displacement Using the Acellular Dermal Matrix Garter Belt.

BACKGROUND: Since the issue of breast implant-associated anaplastic large cell lymphoma, smooth breast implants tend to be the more preferred option in implant-based breast reconstructions, compared to its use previously. The most unfavorable aspect of smooth implants is lateral and inferior displacements, which are more common in patients who undergo breast reconstruction compared to augmentation mammoplasty. Hence, we introduce a prevention method for implant displacement using an acellular dermal matrix garter belt. METHODS: This study is a retrospective review of patients who had undergone implant-based breast reconstruction between April 2019 and December 2020. Some patients who have highly possibility of implant displacement, had undergone the application of an ADM garter belt to prevent lateral or superior displacement. Implant displacement was assessed before and at least 6 months postoperatively. RESULTS: A total of 155 IBR cases were recorded. ADM garter belts were applied in 27 patients (17.4%) who had a high tendency of implant displacement for several reasons, which could be classified into two categories: wide breast pocket (56%) and tight inferomedial breast pocket (44%). The intraoperative average distance of lateral slipping on patients' reconstructed breasts from the chest wall midline in supine position was 3.02 ± 0.81 cm and corrected to1.54 ± 0.69 cm at least 6 months postoperative follow-up. CONCLUSIONS: We utilized an ADM strap as an internalized garter belt to minimize implant displacement. This ADM garter belt combined with capsuloplasty might be an effective way to prevent the displacement of smooth implants in the patients with a greater risk of implant displacement. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors   www.springer.com/00266.

New Bone Formation in the Whole Decellularized Cortical Bone Scaffold Using the Model of Revitalizing a Haversian System.

ABSTRACT: Decellularized allogeneic bone chips act as scaffolds for bone tissue regeneration. Owing to their lack of osteogenic potentials compared to autologous bone graft, decellularized bone scaffolds (DBSs) have applied only to small partial bone defects in clinical settings. Furthermore, only decellularized cancellous bone chips have been limitedly used for the purpose of bone regeneration. The cortical bone has less porosity and less osteogenic materials such as bone morphogenetic proteins in comparison with cancellous bone. In this study, we tried to accelerate new bone formation within the decellularized cortical bone scaffold using a vascular pedicle as an in vivo bioreactor.Forty DBSs were divided into 4 groups with different conditionings (DBS+ demineralized bone matrix [DBM], DBS+DBM+me+mesenchymal stem cells, DBS+DBM+vascular pedicle, and DBS+DBM+vascular pedicle+mesenchymal stem cells) and implanted into the back of 5 rabbits. Half of the DBSs were examined at 8 weeks and the other half at 16 weeks to determine vascularization level and osteogenesis within each group. New bone formation and bone-forming cells related to osteogenesis were observed via histological staining. Inclusion of the vascular pedicle resulted in larger areas of bone regeneration. With time, osteon structures became more prominent in groups containing the vascular pedicle.In summary, vascularized DBSs combined with a vascular pedicle have shown promising results for bone regeneration, thereby representing potential therapeutic alternatives for autologous bone grafts or bone tissue free transfer in large or segmental bone defects. In addition, demineralized whole cortical bone matrix along with vascular pedicle and various bone inductive materials, such as DBM and recombinant human bone morphogenetic protein-2, may be an additional new option of an ideal osteoinductive system.

Nipple Reconstruction Using the Semilunar Flap and Omega-shaped Acellular Dermal Matrix Strut.

BACKGROUND: Various operative methods exist for nipple reconstruction. Selection of an appropriate skin flap and core strut material is imperative in achieving a satisfactory outcome in nipple reconstruction. Long-term maintenance of nipple projection requires further investigation by surgeons. We propose a new technique that uses a semilunar flap and omega-shaped acellular dermal matrix (ADM). METHODS: Total 53 nipples were reconstructed by this method. An omega-shaped ADM strut was inserted into the barrel made by a semilunar flap. The footplates of omega-shaped ADM struts were spread out under the subcutaneous tissue of the donor site of the semilunar flap to support the dome of the omega strut. RESULTS: The mean maintenance rate of nipple projection was 95.12 ± 6.30% at 3 weeks, 80.60 ± 8.93% at 3 months, and 71.70 ± 8.67% at 6 months postoperatively when compared to the projection observed in the immediate postoperative period. Thirty-five patients (66.0%) showed a maintenance rate over 70% at 6 months post operation, with most patients (94.3%) demonstrating a maintenance rate greater than 60%. CONCLUSIONS: Our study with the omega-shaped ADM strut showed superior maintenance rates of projection when compared to other studies on that used AlloDerm® as a core strut for nipple reconstruction. Omega-shaped struts, when made with cross-linked thick ADM, supported the skin flap quite well. We propose that our method combining the semilunar flap with an omega-shaped ADM may be a good option for nipple reconstruction. LEVEL OF EVIDENCE IV: "This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors   www.springer.com/00266 ."

Six-well plate-based colony-forming efficacy assay and Co-Culture application to assess toxicity of metal oxide nanoparticles.

The development of a universal, label-free, and reliable in vitro toxicity testing method for nanoparticles is urgent because most nanoparticles can interfere with toxicity assays. In this regard, the colony-forming efficacy (CFE) assay has been suggested as a suitable in vitro toxicity assay for testing nanoparticles without such interference. Recently, the Organisation for Economic Co-operation and Development (OECD) developed a 60 × 15 mm Petri dish-based CFE assay for testing nanoparticles in MDCK-1 cells. However, further investigations are needed, including testing with other cell types, at a smaller scale for greater efficiency, and the application of the co-culture technique. In this study, we selected TiO2, CuO, CeO2, and SiO2 as test nanoparticles and successfully developed a 6-well plate-based CFE assay using HepG2 and A549 cells and a co-culture assay for combinations of HepG2 cells and THP-1 macrophages or A549 cells and THP-1 monocytes. The results suggest that the 6-wellplate-based CFE assay for HepG2 and A549 cells can be applied to nanoparticles, but the co-culture CFE assay has limitations in that it is not different from the single culture study, and it inhibits colony-formation by A549 cells in the presence of macrophages; this warrant further study.

Effect of Pulmonary Inflammation by Surface Functionalization of Zinc Oxide Nanoparticles.

Zinc oxide nanoparticles (ZnO NPs) are used in various industries such as food additives, cosmetics, and biomedical applications. In this study, we evaluated lung damage over time by three types of ZnO NPs (L-serine, citrate, and pristine) following the regulation of functional groups after a single intratracheal instillation to rats. The three types of ZnO NPs showed an acute inflammatory reaction with increased LDH and inflammatory cell infiltration in the alveoli 24 h after administration. Especially in treatment with L-serine, citrate ZnO NPs showed higher acute granulocytic inflammation and total protein induction than the pristine ZnO NPs at 24 h. The acute inflammatory reaction of the lungs recovered on day 30 with bronchoalveolar fibrosis. The concentrations of IL-4, 6, TNF-α, and eotaxin in the bronchoalveolar lavage fluid (BALF) decreased over time, and the levels of these inflammation indicators are consistent with the following inflammatory cell data and acute lung inflammation by ZnO NP. This study suggests that single inhalation exposure to functionalized ZnO NPs may cause acute lung injury with granulocytic inflammation. Although it can recover 30 days after exposure, acute pulmonary inflammation in surface functionalization means that additional studies of exposure limits are needed to protect the workers that produce it.

The Research of Toxicity and Sensitization Potential of PEGylated Silver and Gold Nanomaterials.

Polyethylene glycol (PEG) is a polymer used for surface modification of important substances in the modern pharmaceutical industry and biopharmaceutical fields. Despite the many benefits of PEGylation, there is also the possibility that the application and exposure of the substance may cause adverse effects in the body, such as an immune response. Therefore, we aimed to evaluate the sensitization responses that could be induced through the intercomparison of nanomaterials of the PEG-coated group with the original group. We selected gold/silver nanomaterials (NMs) for original group and PEGylated silver/gold NMs in this study. First, we measured the physicochemical properties of the four NMs, such as size and zeta potential under various conditions. Additionally, we performed the test of the NM's sensitization potential using the KeratinoSens™ assay for in vitro test method and the LLNA: 5-bromo-2-deoxyuridine (BrdU)-FCM for in vivo test method. The results showed that PEGylated-NMs did not lead to skin sensitization according to OECD TG 442 (alternative test for skin sensitization). In addition, gold nanomaterial showed that cytotoxicity of PEGylated-AuNMs was lower than AuNMs. These results suggest the possibility that PEG coating does not induce an immune response in the skin tissue and can lower the cytotoxicity of nanomaterials.

Toxicological Assessment of Bromochlorophene: Single and Repeated-Dose 28-Day Oral Toxicity, Genotoxicity, and Dermal Application in Sprague-Dawley Rats.

Bromochlorophene (BCP) has shown good properties in sterilization and antibacterial activity and is widely used as a household chemical. We evaluated the genotoxicity, single and repeated-dose 28-day oral toxicity, and dermal application of a BCP suspension in Sprague-Dawley (SD) rats. For the single-dose toxicity study, a dose of 25-1,000 mg per kg of bodyweight (mg/kg b.w.) of BCP was given once orally to SD rats. Mortality and clinical signs were observed and recorded for the first 30 min after treatment, at 4 h post-administration, and then at least once daily for 14 days after administration. For the repeated-dose 28-day toxicity study, the high dose was set at 1,000 mg/kg b.w. and the middle, middle-low, and low dose were set to 500, 250, and 125 mg/kg, respectively. Hematology and biochemistry parameters were examined. Gross pathologic and histopathologic examinations were performed on selected tissues from all animals. A bacterial reverse mutation assay, in vitro chromosomal aberration assay, and in vivo micronucleus assay were performed to assess genotoxicity-dermal application exposure assessment of BCP in rats. A high oral approximate lethal dose (ALD) of 1,000 mg/kg was observed in the single-dose toxicity test. During the repeated-dose 28-day time period, most animal deaths after administration occurred during the first 3 weeks. The 1,000 mg/kg b.w. oral dose caused the death of six male rats (6/7) and four female rats (4/7). At 500 mg/kg b.w., the female rats showed mortality (1/7). For the biochemistry assays, cholesterol was increased significantly compared to vehicle in both sexes in the 250 and 500 mg/kg groups. Histopathological changes with treatment-related findings were observed in the pancreas in female rats treated with a high dose of BCP compared with the vehicle group. BCP showed no genotoxic effect. These data suggested that the ALD of BCP, estimated as a non-genotoxic substance, was over 1,000 mg/kg b.w. in the single-dose toxicity study, and the NOAEL of BCP was considered to be 250 mg/kg b.w. for male and female rats after repeated oral administration for 28 days under the present study conditions.

Skin Sensitization Potential and Cellular ROS-Induced Cytotoxicity of Silica Nanoparticles.

Nowadays, various industries using nanomaterials are growing rapidly, and in particular, as the commercialization and use of nanomaterials increase in the cosmetic field, the possibility of exposure of nanomaterials to the skin of product producers and consumers is increasing. Due to the unique properties of nanomaterials with a very small size, they can act as hapten and induce immune responses and skin sensitization, so accurate identification of toxicity is required. Therefore, we selected silica nanomaterials used in various fields such as cosmetics and biomaterials and evaluated the skin sensitization potential step-by-step according to in-vitro and in-vivo alternative test methods. KeratinoSensTM cells of modified keratinocyte and THP-1 cells mimicking dendritic-cells were treated with silica nanoparticles, and their potential for skin sensitization and cytotoxicity were evaluated, respectively. We also confirmed the sensitizing ability of silica nanoparticles in the auricle-lymph nodes of BALB/C mice by in-vivo analysis. As a result, silica nanoparticles showed high protein binding and reactive oxygen species (ROS) mediated cytotoxicity, but no significant observation of skin sensitization indicators was observed. Although more studies are needed to elucidate the mechanism of skin sensitization by nanomaterials, the results of this study showed that silica nanoparticles did not induce skin sensitization.

Flow cytometric evaluation of the potential of metal oxide nanoparticles for skin sensitization using 5-Bromo-2-deoxyuridine.

Although skin sensitization potential of various chemicals has been extensively studied, there are only a few reports on nanoparticles induced skin sensitization. Aiming to fill this lacuna, in this study we evaluated the potential of metal oxide nanoparticles (NPs) to induce skin sensitization with flow cytometry. Seven different metal oxide NPs, including copper oxide, cobalt oxide, nickel oxide, titanium oxide, cerium oxide, iron oxide, and zinc oxide were applied to Balb/c mice. After selecting the proper vehicle, the NPs were applied, and the skin sensitization potential were assessed using 5-bromo-2-deoxyuridine with flow cytometry. Physiochemical properties such as hydrodynamic size, polydispersity, and zeta potential were measured for the NPs prior to the tests. All the seven metal oxide NPs studied showed negative responses for skin sensitization potential. These results suggest that the OECD TG 442B using 5-bromo-2-deoxyuridine with flow cytometry can be applied to evaluate the potential of NPs for skin sensitization.

Corrigendum: Copper and Cobalt Ions Released From Metal Oxide Nanoparticles Trigger Skin Sensitization.

[This corrects the article DOI: 10.3389/fphar.2021.627781.].

Skin Sensitization Evaluation of Carbon-Based Graphene Nanoplatelets.

Graphene nanoplatelets (GNPs) are one of the major types of carbon based nanomaterials that have different industrial and biomedical applications. There is a risk of exposure to GNP material in individuals involved in their large-scale production and in individuals who use products containing GNPs. Determining the exact toxicity of GNP nanomaterials is a very important agenda. This research aimed to evaluate the skin sensitization potentials induced by GNPs using two types of alternative to animal testing. We analyzed the physicochemical characteristics of the test material by selecting a graphene nanomaterial with a nano-size on one side. Thereafter, we evaluated the skin sensitization effect using an in vitro and an in vivo alternative test method, respectively. As a result, we found that GNPs do not induce skin sensitization. In addition, it was observed that the administration of GNPs did not induce cytotoxicity and skin toxicity. This is the first report of skin sensitization as a result of GNPs obtained using alternative test methods. These results suggest that GNP materials do not cause skin sensitization, and these assays may be useful in evaluating the skin sensitization of some nanomaterials.

Evaluation of the skin sensitization potential of metal oxide nanoparticles using the ARE-Nrf2 Luciferase KeratinoSensTM assay.

Numerous studies have reported the potential of chemicals for inducing skin sensitization; however, few studies have examined skin sensitization induced by nanomaterials. This study aimed to evaluate skin sensitization induced by metal oxide nanoparticles (NPs) using the ARE-Nrf2 Luciferase KeratinoSens™ assay. Seven different metal oxide NPs, including copper oxide, cobalt oxide, nickel oxide, titanium oxide, cerium oxide, iron oxide, and zinc oxide, were assessed on KeratinoSens™ cells. We selected an appropriate vehicle among three vehicles (DMSO, DW, and culture medium) by assessing the hydrodynamic size at vehicle selection process. Seven metal oxide NPs were analyzed, and their physicochemical properties, including hydrodynamic size, polydispersity, and zeta potential, were determined in the selected vehicle. Thereafter, we assessed the sensitization potential of the NPs using the ARE-Nrf2 Luciferase KeratinoSens™ assay. Copper oxide NPs induced a positive response, whereas cobalt oxide, nickel oxide, titanium oxide, cerium oxide, iron oxide, and zinc oxide NPs induced no response. These results suggest that the ARE-Nrf2 Luciferase KeratinoSens™ assay may be useful for evaluating the potential for skin sensitization induced by metal oxide NPs.

Copper and Cobalt Ions Released from Metal Oxide Nanoparticles Trigger Skin Sensitization.

Human skins are exposed to nanomaterials in everyday life from various sources such as nanomaterial-containing cosmetics, air pollutions, and industrial nanomaterials. Nanomaterials comprising metal haptens raises concerns about the skin sensitization to nanomaterials. In this study, we evaluated the skin sensitization of nanomaterials comparing metal haptens in vivo and in vitro. We selected five metal oxide NPs, containing copper oxide, cobalt monoxide, cobalt oxide, nickel oxide, or titanium oxide, and two types of metal chlorides (CoCl2 and CuCl2), to compare the skin sensitization abilities between NPs and the constituent metals. The materials were applied to KeratinoSensTM cells for imitated skin-environment setting, and luciferase induction and cytotoxicity were evaluated at 48 h post-incubation. In addition, the response of metal oxide NPs was confirmed in lymph node of BALB/C mice via an in vivo method. The results showed that CuO and CoO NPs induce a similar pattern of positive luciferase induction and cytotoxicity compared to the respective metal chlorides; Co3O4, NiO, and TiO2 induced no such response. Collectively, the results implied fast-dissolving metal oxide (CuO and CoO) NPs release their metal ion, inducing skin sensitization. However, further investigations are required to elucidate the mechanism underlying NP-induced skin sensitization. Based on ion chelation data, metal ion release was confirmed as the major "factor" for skin sensitization.