Sensor Selection and Chemo-Sensory Optimization: Toward an Adaptable Chemo-Sensory System

Over the past two decades, despite the tremendous research on chemical sensors and machine olfaction to develop micro-sensory systems that will accomplish the growing existent needs in personal health (implantable sensors), environment monitoring (widely distributed sensor networks), and security/threat detection (chemo/bio warfare agents), simple, low-cost molecular sensing platforms capable of long-term autonomous operation remain beyond the current state-of-the-art of chemical sensing. A fundamental issue within this context is that most of the chemical sensors depend on interactions between the targeted species and the surfaces functionalized with receptors that bind the target species selectively, and that these binding events are coupled with transduction processes that begin to change when they are exposed to the messy world of real samples. With the advent of fundamental breakthroughs at the intersection of materials science, micro- and nano-technology, and signal processing, hybrid chemo-sensory systems have incorporated tunable, optimizable operating parameters, through which changes in the response characteristics can be modeled and compensated as the environmental conditions or application needs change. The objective of this article, in this context, is to bring together the key advances at the device, data processing, and system levels that enable chemo-sensory systems to “adapt” in response to their environments. Accordingly, in this review we will feature the research effort made by selected experts on chemical sensing and information theory, whose work has been devoted to develop strategies that provide tunability and adaptability to single sensor devices or sensory array systems. Particularly, we consider sensor-array selection, modulation of internal sensing parameters, and active sensing. The article ends with some conclusions drawn from the results presented and a visionary look toward the future in terms of how the field may evolve

Using a Second Order Sigma-Delta Control to Improve the Performance of Metal-Oxide Gas Sensors

Controls of surface potential have been proposed to accelerate the time response of MOX gas sensors. These controls use temperature modulations and a feedback loop based on first-order sigma-delta modulators to keep constant the surface potential. Changes in the surrounding gases, therefore, must be compensated by average temperature produced by the control loop, which is the new output signal. The purpose of this paper is to present a second order sigma-delta control of the surface potential for gas sensors. With this new control strategy, it is possible to obtain a second order zero of the quantization noise in the output signal. This provides a less noisy control of the surface potential, while at the same time some undesired effects of first order modulators, such as the presence of plateaus, are avoided. Experiments proving these performance improvements are presented using a gas sensor made of tungsten oxide nanowires. Plateau avoidance and second order noise shaping is shown with ethanol measurements.Postprint (author's final draft

Identification of Tequila with an Array of ZnO Thin Films: A Simple and Cost-Effective Method

Se trata de identificar calidad de bebidas alcohólicasAn array of ZnO thin film sensors was obtained by thermal oxidation of physical vapor deposited thin Zn films. Different conditions of the thermal treatment (duration and temperature) were applied in view of obtaining ZnO sensors with different gas sensing properties. Films having undergone a long thermal treatment exhibited high responses to low ethanol concentrations, while short thermal treatments generally led to sensors with high ethanol sensitivity. The sensor array was used to distinguish among Tequilas and Agave liquor. Linear discriminant analysis and the multilayer perceptron neural network reached 100% and 86.3% success rates in the discrimination between real Tequila and Agave liquor and in the identification of Tequila brands, respectively. These results are promising for the development of an inexpensive tool offering low complexity and cost of analysis for detecting fraud in spirits.Beca CONACyT- Bilateral de estudios de Doctorad

Gas Sensing Properties of Perovskite Decorated Graphene at Room Temperature

[EN] This paper explores the gas sensing properties of graphene nanolayers decorated with lead halide perovskite (CH3NH3PbBr3) nanocrystals to detect toxic gases such as ammonia (NH3) and nitrogen dioxide (NO2). A chemical-sensitive semiconductor film based on graphene has been achieved, being decorated with CH3NH3PbBr3 perovskite (MAPbBr3) nanocrystals (NCs) synthesized, and characterized by several techniques, such as field emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Reversible responses were obtained towards NO2 and NH3 at room temperature, demonstrating an enhanced sensitivity when the graphene is decorated by MAPbBr3 NCs. Furthermore, the effect of ambient moisture was extensively studied, showing that the use of perovskite NCs in gas sensors can become a promising alternative to other gas sensitive materials, due to the protective character of graphene, resulting from its high hydrophobicity. Besides, a gas sensing mechanism is proposed to understand the effects of MAPbBr3 sensing propertiesThis work was funded in part by MINECO, MICINN and FEDER via grants no. RTI2018-101580-B-I00, by AGAUR under grant. 2017SGR 418 J.C.C gratefully acknowledges a doctoral fellowship from URV under the Marti i Franques fellowship program. E.L. is supported by the Catalan institution for Research and Advanced Studies via the 2012 and 2018 Editions of the ICREA Academia Award. P.A. acknowledges the financial support from the Spanish Government through 'Severo Ochoa"(SEV-2016-0683, MINECO) and PGC2018-099744-B-I00 (MCIU/AEI/FEDER, UE), and R.G.A. acknowledges FPI scholarship the Spanish Government-MINECO for a (TEC2015-74405-JIN), MAT2015-69669-P.Casanova-Cháfer, J.; García-Aboal, R.; Atienzar Corvillo, PE.; Llobet, E. (2019). Gas Sensing Properties of Perovskite Decorated Graphene at Room Temperature. Sensors. 19(20):1-14. https://doi.org/10.3390/s19204563S11419207 Million Premature Deaths Annually Linked to Air Pollution https://www.who.int/mediacentre/news/releases/2014/air-pollution/en/Hansen, J., Sato, M., Ruedy, R., Lacis, A., & Oinas, V. (2000). Global warming in the twenty-first century: An alternative scenario. Proceedings of the National Academy of Sciences, 97(18), 9875-9880. doi:10.1073/pnas.170278997Ibañez, F. J., & Zamborini, F. P. (2011). Chemiresistive Sensing with Chemically Modified Metal and Alloy Nanoparticles. Small, 8(2), 174-202. doi:10.1002/smll.201002232Mirzaei, A., Leonardi, S. G., & Neri, G. (2016). Detection of hazardous volatile organic compounds (VOCs) by metal oxide nanostructures-based gas sensors: A review. Ceramics International, 42(14), 15119-15141. doi:10.1016/j.ceramint.2016.06.145Zaidi, N. A., Tahir, M. W., Vellekoop, M. J., & Lang, W. (2017). A Gas Chromatographic System for the Detection of Ethylene Gas Using Ambient Air as a Carrier Gas. Sensors, 17(10), 2283. doi:10.3390/s17102283Meng, F.-L., Guo, Z., & Huang, X.-J. (2015). Graphene-based hybrids for chemiresistive gas sensors. TrAC Trends in Analytical Chemistry, 68, 37-47. doi:10.1016/j.trac.2015.02.008Miller, D. R., Akbar, S. A., & Morris, P. A. (2014). Nanoscale metal oxide-based heterojunctions for gas sensing: A review. Sensors and Actuators B: Chemical, 204, 250-272. doi:10.1016/j.snb.2014.07.074Scott, S. M., James, D., & Ali, Z. (2006). Data analysis for electronic nose systems. Microchimica Acta, 156(3-4), 183-207. doi:10.1007/s00604-006-0623-9Rodríguez-Pérez, L., Herranz, M. Á., & Martín, N. (2013). The chemistry of pristine graphene. Chemical Communications, 49(36), 3721. doi:10.1039/c3cc38950bPrezioso, S., Perrozzi, F., Giancaterini, L., Cantalini, C., Treossi, E., Palermo, V., … Ottaviano, L. (2013). Graphene Oxide as a Practical Solution to High Sensitivity Gas Sensing. The Journal of Physical Chemistry C, 117(20), 10683-10690. doi:10.1021/jp3085759Lipatov, A., Varezhnikov, A., Wilson, P., Sysoev, V., Kolmakov, A., & Sinitskii, A. (2013). Highly selective gas sensor arrays based on thermally reduced graphene oxide. Nanoscale, 5(12), 5426. doi:10.1039/c3nr00747bVarghese, S. S., Lonkar, S., Singh, K. K., Swaminathan, S., & Abdala, A. (2015). Recent advances in graphene based gas sensors. Sensors and Actuators B: Chemical, 218, 160-183. doi:10.1016/j.snb.2015.04.062Rodner, M., Puglisi, D., Ekeroth, S., Helmersson, U., Shtepliuk, I., Yakimova, R., … Eriksson, J. (2019). Graphene Decorated with Iron Oxide Nanoparticles for Highly Sensitive Interaction with Volatile Organic Compounds. Sensors, 19(4), 918. doi:10.3390/s19040918Kaniyoor, A., Imran Jafri, R., Arockiadoss, T., & Ramaprabhu, S. (2009). Nanostructured Pt decorated graphene and multi walled carbon nanotube based room temperature hydrogen gas sensor. Nanoscale, 1(3), 382. doi:10.1039/b9nr00015aSeekaew, Y., Lokavee, S., Phokharatkul, D., Wisitsoraat, A., Kerdcharoen, T., & Wongchoosuk, C. (2014). Low-cost and flexible printed graphene–PEDOT:PSS gas sensor for ammonia detection. Organic Electronics, 15(11), 2971-2981. doi:10.1016/j.orgel.2014.08.044Kang, M.-A., Ji, S., Kim, S., Park, C.-Y., Myung, S., Song, W., … An, K.-S. (2018). Highly sensitive and wearable gas sensors consisting of chemically functionalized graphene oxide assembled on cotton yarn. RSC Advances, 8(22), 11991-11996. doi:10.1039/c8ra01184bFine, G. F., Cavanagh, L. M., Afonja, A., & Binions, R. (2010). Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring. Sensors, 10(6), 5469-5502. doi:10.3390/s100605469Sun, D., Luo, Y., Debliquy, M., & Zhang, C. (2018). Graphene-enhanced metal oxide gas sensors at room temperature: a review. Beilstein Journal of Nanotechnology, 9, 2832-2844. doi:10.3762/bjnano.9.264Llobet, E. (2013). Gas sensors using carbon nanomaterials: A review. Sensors and Actuators B: Chemical, 179, 32-45. doi:10.1016/j.snb.2012.11.014Correa-Baena, J.-P., Abate, A., Saliba, M., Tress, W., Jesper Jacobsson, T., Grätzel, M., & Hagfeldt, A. (2017). The rapid evolution of highly efficient perovskite solar cells. Energy & Environmental Science, 10(3), 710-727. doi:10.1039/c6ee03397kSun, S., Salim, T., Mathews, N., Duchamp, M., Boothroyd, C., Xing, G., … Lam, Y. M. (2014). The origin of high efficiency in low-temperature solution-processable bilayer organometal halide hybrid solar cells. Energy Environ. Sci., 7(1), 399-407. doi:10.1039/c3ee43161dJuarez-Perez, E. J., Ono, L. K., Maeda, M., Jiang, Y., Hawash, Z., & Qi, Y. (2018). Photodecomposition and thermal decomposition in methylammonium halide lead perovskites and inferred design principles to increase photovoltaic device stability. Journal of Materials Chemistry A, 6(20), 9604-9612. doi:10.1039/c8ta03501fChen, H., Zhang, M., Bo, R., Barugkin, C., Zheng, J., Ma, Q., … Tricoli, A. (2017). Superior Self‐Powered Room‐Temperature Chemical Sensing with Light‐Activated Inorganic Halides Perovskites. Small, 14(7), 1702571. doi:10.1002/smll.201702571Kakavelakis, G., Gagaoudakis, E., Petridis, K., Petromichelaki, V., Binas, V., Kiriakidis, G., & Kymakis, E. (2017). Solution Processed CH3NH3PbI3–xClx Perovskite Based Self-Powered Ozone Sensing Element Operated at Room Temperature. ACS Sensors, 3(1), 135-142. doi:10.1021/acssensors.7b00761Bao, C., Yang, J., Zhu, W., Zhou, X., Gao, H., Li, F., … Zou, Z. (2015). A resistance change effect in perovskite CH3NH3PbI3 films induced by ammonia. Chemical Communications, 51(84), 15426-15429. doi:10.1039/c5cc06060eZhuang, Y., Yuan, W., Qian, L., Chen, S., & Shi, G. (2017). High-performance gas sensors based on a thiocyanate ion-doped organometal halide perovskite. Physical Chemistry Chemical Physics, 19(20), 12876-12881. doi:10.1039/c7cp01646hStoeckel, M.-A., Gobbi, M., Bonacchi, S., Liscio, F., Ferlauto, L., Orgiu, E., & Samorì, P. (2017). Reversible, Fast, and Wide-Range Oxygen Sensor Based on Nanostructured Organometal Halide Perovskite. Advanced Materials, 29(38), 1702469. doi:10.1002/adma.201702469Zhu, R., Zhang, Y., Zhong, H., Wang, X., Xiao, H., Chen, Y., & Li, X. (2019). High-performance room-temperature NO2 sensors based on CH3NH3PbBr3 semiconducting films: Effect of surface capping by alkyl chain on sensor performance. Journal of Physics and Chemistry of Solids, 129, 270-276. doi:10.1016/j.jpcs.2019.01.020Acik, M., & Darling, S. B. (2016). Graphene in perovskite solar cells: device design, characterization and implementation. Journal of Materials Chemistry A, 4(17), 6185-6235. doi:10.1039/c5ta09911kChristians, J. A., Miranda Herrera, P. A., & Kamat, P. V. (2015). Transformation of the Excited State and Photovoltaic Efficiency of CH3NH3PbI3 Perovskite upon Controlled Exposure to Humidified Air. Journal of the American Chemical Society, 137(4), 1530-1538. doi:10.1021/ja511132aLeguy, A. M. A., Hu, Y., Campoy-Quiles, M., Alonso, M. I., Weber, O. J., Azarhoosh, P., … Barnes, P. R. F. (2015). Reversible Hydration of CH3NH3PbI3 in Films, Single Crystals, and Solar Cells. Chemistry of Materials, 27(9), 3397-3407. doi:10.1021/acs.chemmater.5b00660O’Keeffe, P., Catone, D., Paladini, A., Toschi, F., Turchini, S., Avaldi, L., … Di Carlo, A. (2019). Graphene-Induced Improvements of Perovskite Solar Cell Stability: Effects on Hot-Carriers. Nano Letters, 19(2), 684-691. doi:10.1021/acs.nanolett.8b03685Berhe, T. A., Su, W.-N., Chen, C.-H., Pan, C.-J., Cheng, J.-H., Chen, H.-M., … Hwang, B.-J. (2016). Organometal halide perovskite solar cells: degradation and stability. Energy & Environmental Science, 9(2), 323-356. doi:10.1039/c5ee02733kLee, G. Y., Yang, M. Y., Kim, D., Lim, J., Byun, J., Choi, D. S., … Kim, S. O. (2019). Nitrogen‐Dopant‐Induced Organic–Inorganic Hybrid Perovskite Crystal Growth on Carbon Nanotubes. Advanced Functional Materials, 29(30), 1902489. doi:10.1002/adfm.201902489Fu, X., Jiao, S., Dong, N., Lian, G., Zhao, T., Lv, S., … Cui, D. (2018). A CH3NH3PbI3 film for a room-temperature NO2 gas sensor with quick response and high selectivity. RSC Advances, 8(1), 390-395. doi:10.1039/c7ra11149eGupta, N., Nanda, O., Grover, R., & Saxena, K. (2018). A new inorganic-organic hybrid halide perovskite thin film based ammonia sensor. Organic Electronics, 58, 202-206. doi:10.1016/j.orgel.2018.04.015Air Quality Standards https://ec.europa.eu/environment/air/quality/standards.htmCommission Directive 2000/39/EC https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:02000L0039-20100108&from=ENSchmidt, L. C., Pertegás, A., González-Carrero, S., Malinkiewicz, O., Agouram, S., Mínguez Espallargas, G., … Pérez-Prieto, J. (2014). Nontemplate Synthesis of CH3NH3PbBr3 Perovskite Nanoparticles. Journal of the American Chemical Society, 136(3), 850-853. doi:10.1021/ja4109209Yang, G., Kim, B.-J., Kim, K., Han, J. W., & Kim, J. (2015). Energy and dose dependence of proton-irradiation damage in graphene. RSC Advances, 5(40), 31861-31865. doi:10.1039/c5ra03551aD’Acunto, G., Ripanti, F., Postorino, P., Betti, M. G., Scardamaglia, M., Bittencourt, C., & Mariani, C. (2018). Channelling and induced defects at ion-bombarded aligned multiwall carbon nanotubes. Carbon, 139, 768-775. doi:10.1016/j.carbon.2018.07.032Johra, F. T., Lee, J.-W., & Jung, W.-G. (2014). Facile and safe graphene preparation on solution based platform. Journal of Industrial and Engineering Chemistry, 20(5), 2883-2887. doi:10.1016/j.jiec.2013.11.022Ganesan, K., Ghosh, S., Gopala Krishna, N., Ilango, S., Kamruddin, M., & Tyagi, A. K. (2016). A comparative study on defect estimation using XPS and Raman spectroscopy in few layer nanographitic structures. Physical Chemistry Chemical Physics, 18(32), 22160-22167. doi:10.1039/c6cp02033jRoy, S., Das, T., Ming, Y., Chen, X., Yue, C. Y., & Hu, X. (2014). Specific functionalization and polymer grafting on multiwalled carbon nanotubes to fabricate advanced nylon 12 composites. Journal of Materials Chemistry A, 2(11), 3961. doi:10.1039/c3ta14528jDatsyuk, V., Kalyva, M., Papagelis, K., Parthenios, J., Tasis, D., Siokou, A., … Galiotis, C. (2008). Chemical oxidation of multiwalled carbon nanotubes. Carbon, 46(6), 833-840. doi:10.1016/j.carbon.2008.02.012Kumar, P. V., Bernardi, M., & Grossman, J. C. (2013). The Impact of Functionalization on the Stability, Work Function, and Photoluminescence of Reduced Graphene Oxide. ACS Nano, 7(2), 1638-1645. doi:10.1021/nn305507pLiu, J., Durstock, M., & Dai, L. (2014). Graphene oxide derivatives as hole- and electron-extraction layers for high-performance polymer solar cells. Energy Environ. Sci., 7(4), 1297-1306. doi:10.1039/c3ee42963fGeorgakilas, V., Otyepka, M., Bourlinos, A. B., Chandra, V., Kim, N., Kemp, K. C., … Kim, K. S. (2012). Functionalization of Graphene: Covalent and Non-Covalent Approaches, Derivatives and Applications. Chemical Reviews, 112(11), 6156-6214. doi:10.1021/cr3000412Wang, Y., Zhang, Y., Lu, Y., Xu, W., Mu, H., Chen, C., … Bao, Q. (2015). Hybrid Graphene-Perovskite Phototransistors with Ultrahigh Responsivity and Gain. Advanced Optical Materials, 3(10), 1389-1396. doi:10.1002/adom.201500150Lv, C., Hu, C., Luo, J., Liu, S., Qiao, Y., Zhang, Z., … Watanabe, A. (2019). Recent Advances in Graphene-Based Humidity Sensors. Nanomaterials, 9(3), 422. doi:10.3390/nano9030422Casanova-Cháfer, J., Navarrete, E., Noirfalise, X., Umek, P., Bittencourt, C., & Llobet, E. (2018). Gas Sensing with Iridium Oxide Nanoparticle Decorated Carbon Nanotubes. Sensors, 19(1), 113. doi:10.3390/s19010113Fang, H.-H., Adjokatse, S., Wei, H., Yang, J., Blake, G. R., Huang, J., … Loi, M. A. (2016). Ultrahigh sensitivity of methylammonium lead tribromide perovskite single crystals to environmental gases. Science Advances, 2(7). doi:10.1126/sciadv.160053

Optimized Feature Extraction for Temperature-Modulated Gas Sensors

One of the most serious limitations to the practical utilization of solid-state gas sensors is the drift of their signal. Even if drift is rooted in the chemical and physical processes occurring in the sensor, improved signal processing is generally considered as a methodology to increase sensors stability. Several studies evidenced the augmented stability of time variable signals elicited by the modulation of either the gas concentration or the operating temperature. Furthermore, when time-variable signals are used, the extraction of features can be accomplished in shorter time with respect to the time necessary to calculate the usual features defined in steady-state conditions. In this paper, we discuss the stability properties of distinct dynamic features using an array of metal oxide semiconductors gas sensors whose working temperature is modulated with optimized multisinusoidal signals. Experiments were aimed at measuring the dispersion of sensors features in repeated sequences of a limited number of experimental conditions. Results evidenced that the features extracted during the temperature modulation reduce the multidimensional data dispersion among repeated measurements. In particular, the Energy Signal Vector provided an almost constant classification rate along the time with respect to the temperature modulation

Chemical vapour deposited ZnO nanowires for detecting Ethanol and NO2

Randomly oriented ZnO nanowires were grown directly onto alumina substrates having platinum interdigitated screen-printed electrodes via the chemical vapor deposition method using Au as catalyst. Three different Au film thicknesses (i.e., 3, 6 or 12 nm) were used in the growth of nanowires, and their gas sensing properties were studied for ethanol and NO2 as reducing and oxidizing species, respectively. ZnO nanowires grown employing the 6 nm thick layers were the less defective and showed the most stable, repeatable gas sensing properties. Despite ZnO nanowires grown employing the thickest Au layers reached the highest responses under dry conditions, ZnO nanowires grown using the thinnest Au film were more resilient at detecting NO2 in the presence of ambient moisture. The gas sensing results are discussed in light of the defects and the presence of Au impurities in the ZnO nanowires, as revealed by the characterization techniques used, such as X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy and photoluminescence spectroscopy. Promising results were obtained by the implementation of ZnO NWs directly grown over alumina substrates for the detection of ethanol and NO2, substantially ameliorating our previously reported results

The periodontium as a potential cause of orofacial pain: a comprehensive review

Introduction: Orofacial pain of periodontal origin has a wide range of causes, and its high prevalence and negative effect on patients' quality of life make intervention mandatory. This review provides a periodontological overview of the field of orofacial pain, focusing on the entities which involve the periodontal tissues and may be the cause of this pain or discomfort. Methods: The study comprised a literature search of these pathologies conducted in the MEDLINE/PubMed Database. Acute infectious entities such as gingival and periodontal abscesses are emergencies that require a rapid response. Periodontitis associated with endodontic processes, necrotizing periodontal disorders, desquamative gingivitis, gingival recession, and mucogingival herpetic lesions, cause mild to severe pain due to tissue destruction and loss. Other lesions that lead to periodontal discomfort include gingival enlargement and periodontal ligament strains associated with occlusal trauma, parafunctional habit and the impaction of food or foreign bodies. Conclusion: A range of therapeutic, pharmacological and surgical alternatives are available for the management of these injuries. However, the wide variety of causes of orofacial pain or periodontal discomfort may confuse the clinician during diagnosis and may lead to the wrong choice of treatment

Capacity of dental equipment to interfere with cardiac implantable electrical devices

Patients with cardiac implantable electrical devices should take precautions when exposed to electromagnetic fields. Possible interference as a result of proximity to electromagnets or electricity flow from electronic tools employed in clinical odontology remains controversial. The objective of this study was to examine in vitro the capacity of dental equipment to provoke electromagnetic interference in pacemakers and implantable cardioverter defibrillators. Six electronic dental instruments were tested on three implantable cardioverter defibrillators and three pacemakers from different manufacturers. A simulator model, submerged in physiological saline, with elements that reproduced life-size anatomic structures was used. The instruments were analyzed at differing distances and for different time periods of application. The dental instruments studied displayed significant differences in their capacity to trigger electromagnetic interference. Significant differences in the quantity of registered interference were observed with respect to the variables manufacturer, type of cardiac implant, and application distance but not with the variable time of application. The electronic dental equipment tested at a clinical application distance (20 cm) provoked only slight interference in the pacemakers and implantable cardioverter defibrillators employed, irrespective of manufacturer

Treatments to Optimize Dental Implant Surface Topography and Enhance Cell Bioactivity

Osseointegration is a biological process in which histological, surgical, infectious factors, biomechanical load, and the choice of biomaterials all play important roles. In the case of dental implants, the success of this process is also influenced by the design, composition, and properties of the implant surface, which may stimulate cell bioactivity and promote osteoblast adhesion. Currently, the raw materials most frequently used in the manufacture of dental implants are titanium, its alloys, and certain ceramic materials such as zirconia. Multiple macroscopic designs incorporating various diameters, lengths, shapes, and types of screw offer different options for specific clinical situations. The characteristics of implant surfaces have aroused great interest, due to their importance in osseointegration. The different methods used to modify surface properties are classified as additive (i.e., impregnation and coating) or subtractive (i.e., physical, mechanical and chemical methods). The surface characteristics of dental implants also have a significant influence on peri-implant microbiota

On the cellular and molecular mechanisms of drug-induced gingival overgrowth

Introduction:Gingival overgrowth has been linked to multiple factors such as adverse drug effects, inflammation, neoplastic processes, and hereditary gingival fibromatosis. Drug-induced gingival overgrowth is a well-established adverse event. In early stages, this gingival enlargement is usually located in the area of the interdental papilla. Histologically, there is an increase in the different components of the extracellular matrix.Objective:The aim of this manuscript is to describe and analyze the different cellular and molecular agents involved in the pathogenesis of Drug-induced gingival overgrowth.Method:A literature search of the MEDLINE/PubMed database was conducted to identify the mechanisms involved in the process of druginduced gingival overgrowth, with the assistance of a research librarian. We present several causal hypotheses and discuss the advances in the understanding of the mechanisms that trigger this gingival alteration.Results:In vitro studies have revealed phenotypic cellular changes in keratinocytes and fibroblasts and an increase of the extracellular matrix with collagen and glycosaminoglycans. Drug-induced gingival overgrowth confirms the key role of collagenase and integrins, membrane receptors present in the fibroblasts, due to their involvement in the catabolism of collagen. The three drug categories implicated: calcineuron inhibitors (immunosuppressant drugs), calcium channel blocking agents and anticonvulsant drugs appear to present a multifactorial pathogenesis with a common molecular action: the blockage of the cell membrane in the Ca2+/Na+ ion flow. The alteration of the uptake of cellular folic acid, which depends on the regulated channels of active cationic transport and on passive diffusion, results in a dysfunctional degradation of the connective tissue. Certain intermediate molecules such as cytokines and prostaglandins play a role in this pathological mechanism. The concomitant inflammatory factor encourages the appearance of fibroblasts, which leads to gingival fibrosis. Susceptibility to gingival overgrowth in some fibroblast subpopulations is due to phenotypic variability and genetic polymorphism, as shown by the increase in the synthesis of molecules related to the response of the gingival tissue to inducing drugs. The authors present a diagram depicting various mechanisms involved in the pathogenesis of drug-induced gingival overgrowth.Conclusion:Individual predisposition, tissue inflammation, and molecular changes in response to the inducing drug favor the clinical manifestation of gingival overgrowth