Silver nanoparticles, research and development in Mexico: a bibliometric analysis

Abstract

Mexico has been the world’s largest producer of silver for many years, and silver nanoparticles are the most important nanoparticles used in the industry worldwide due to a significant variety of properties. The main goal of this paper was to make a bibliometric analysis of the scientific and productive linkages about silver nanoparticles and their studies, developments, or applications in Mexico. This paper explores and shows the technological transfer of silver nanoparticles from the academic part until its industrial application. We analyzed the scientific publications, academic groups, and technological transfer. We analyzed the obtained data and we done a co-author network array, patent research, and commercial tracking. We found a marked set of researchers studying and developing several materials applied to diverse products range, where the academic production is limited to a number of granted patents. In addition, neither a complete knowledge of the environmental impacts and side effects caused by these particles were found, nor any public policy that regulates its manufacturing. The results suggest opportunities for research, development, application, and academic collaboration on nanoparticles and nanomaterials field, even for legislation and regulation areas. This article shows that Mexico has a good capability to do research and development, in order to generate a propitious environment to scale up the production and commercialization of these technologies on national and international markets, and strengthen collaboration with other countries.

Introduction

Mexico has been the world’s largest producer of silver for many years so far (Bell, s/f; “Mine Production”, s/f; “The World’s Leading Silver Producing Countries”, s/f), with the Fresnillo PLC Company leading the world silver production (“The World’s Leading Silver Producing Countries”, s/f). Nowadays, it is estimated that about 1120 tons of silver nanoparticles (AgNP) are produced per year, and they are used in the industry worldwide (Stensberg et al. 2011). According to the Woodrow Wilson Inventory (Nanotech Project 2019), the number of products that contain AgNP reaches 443 around the world, as well as, 378 products register at the Denmark Nanodatabase (Nanodatabase 2019). Some studies have shown cases on health risks and potential side-effects of using AgNP on consumer products and workplaces (Benn et al. 2010; Kulinowski and Lippy 2011). In this way, there are two perspectives of development that continuously converging: on one side, the advantages and novel applications that AgNP leads, and on the other hand, the effects and impacts that these products will have during their life-cycle on humans and the environment.

Silver nanoparticles are one of the most commonly used nanomaterials (NM; Bastian et al. 2009; Piccinno et al. 2012). They have shown several important characteristics such as electrical, thermal, antimicrobial, optical, and diamagnetic properties, where the most important applications are optical imaging, photothermal therapy, antimicrobial coatings, drug delivery, biochemical sensing, and cancer treatment, among other applications (León-Silva et al. 2016, 2018). However, AgNP are considered by the Environmental Protection Agency (EPA) as a pesticide in some applications (Kulinowski and Lippy 2011). Nevertheless, due to the absence of proper knowledge about their toxicity mechanisms, the wide variety of processes and manufacture products could increase exposure to workers and consumers inevitably. Despite the continuing efforts of different health and environmental protection agencies, to understand the issues and consequences produced by this NM, the current regulatory policy does not establish maximum exposition levels and repercussions that these materials trigger.

In contradistinction to the American and European inventories, in Mexico, there are not institutions, statistics, protocols, or standards that regulate the production, import or use of AgNP. Therefore, this study aims to lay a foundation and provide an outlook of the development of AgNP in the country, which is ranked as second place on Research and Development (R&D) of nanotechnologies (NT) in Latin America (Kay and Shapira 2009). To analyze the research and production of this material, the areas in which it is implicated and the socio-environmental effects that it implies when it scales until commercial applications, an overhaul of three fields in a value chain was done. A bibliometric analysis was done on published articles, academic groups, and co-author network for the R&D; in the intellectual property field, a patent search with its application areas was done, and finally, the manufacturing companies and consumer products searching was done for the technological transfer section also. As a result, it was found that the ‘Universidad Nacional Autónoma de Mexico’ (UNAM), ‘Instituto Politécnico Nacional’ (IPN), and the ‘Universidad Autónoma de San Luis Potosí’ (UASLP) have a large group of researchers developing and performing several investigations on the production of materials embedded or coated with AgNP. These materials are made for medical, electronics and homeware use, as shoe inserts, wounds, washing machines, vacuums, refrigerators, hair straighteners, and cleaning products.

The main goal of this study is to explore and show the technological transfer of silver nanoparticles from the academic part until its industrial application through of bibliometric analysis of the scientific and productive linkages about silver nanoparticles and their studies, developments, or applications in Mexico. There is not information about the academic activity and its relationship with technological transfer in the AgNP field. In addition, this article offers to open the opportunities for collaboration on their several interrelationships such as academic—academic, academic—industries, academic—government on national and international levels to give openings for several markets and strengthen collaborations with other countries.

Methodology and data

Study of several sources of information

Firstly, the R&D data were obtained using three strategies, which are articles and patents search, academic groups, and commercialization products, and a bibliometric analysis was implemented. For the bibliometric analysis, an advanced search was done to find who leads the scientific research on AgNP. This was implemented through published articles analysis, using the Web of Science (WoS) Core Collection database, Scival and Scopus databases as well, mainly; with the keywords: ‘nano*’ and ‘silver’ in the topic (TS) field, which includes the title, abstract, keywords, author, and indexer. This information was used to create an array with all AgNP published articles from 2009 to 2019 period with at least one author affiliated with a Mexican institution, including public and private universities, research centres, government agencies, and enterprises. Once, the data matrix was obtained, several filters were carried out with keywords that allowed us to define the methods of synthesis, characterization, applications, and most exposed elements. The categories for each topic are illustrated in Table 1. The timespan was selected because the EPA (in August, 2008) took the first steps to directly regulate the potential environmental, health, and safety risks associated with the manufacture and use of NM, becoming that the turning point for impact and regulation studies.

Table 1 Topics and keywords used for data searches on AgNP

Study by academic groups

Secondly, all academic groups of the ‘Programa para el Desarrollo Profesional Docente’ (PRODEP, Professional Development Program for Professors) of the ‘Secretaría de Educación Pública’ (SEP, Ministry of Public Education) that promote research areas associated with nanotechnology and AgNP were examined. The PRODEP program catalogues the researchers and their studies interests affiliated with most public institutions of higher education in Mexico (Public State Universities, Polytechnic Universities, Technological Universities, Federal Technological Institutes, Decentralized Technological Institutes, and Normal Schools). The following table (Table 2) illustrates the filters used for processing all data.

Table 2 Searching method for filtering data from PRODEP Academic groups

For management the data matrix with the bibliometric material of the scientific knowledge derived from previous research in AgNP, a co-author network was designed using Gephi software, version 0.9.1 (https://gephi.org/), which is an open software for exploring, elaborating, and manipulating networks (Bastian et al. 2009), that illustrate the centrality of the researchers, the number of relationships among them, as well as, the institutions and communities as part of this technological category.

For the intellectual property field, a search of patent applications and granted patents was done. It was carried out by using the advanced search from the ‘Instituto Mexicano de la Propiedad Intelectual’ (IMPI, Mexican Institute of Intellectual Property) database. On this one, Mexican applications and granted patents were searched under the same period (2009–2019) as the bibliometric analysis. The Table 3 lists the searching parameters performed. Once the results were compiled, a manual analysis was conducted for each application to exclude those who did not have a direct relationship with the subject. The results were analysed and categorized into their status.

Table 3 Keywords used for searching patents on AgNP

The technological transfer stage was done through the identification of companies in Mexico that declare containing AgNP in their products. It was manually compiled researching the terms silver and nano* on the World Wide Web as filter parameters for Mexico, and consulting the Nano-economy inventory of companies (https://micrositios.cinvestav.mx/nano/Mapa) also. After that, it was explored every company and their products in detail, which the application area and the company localization for the searching of each type of product was implied. Sumarising, all searches were done consulting several sources, such as Web of Science (WoS) Core Collection database, Scival, and Scopus databases for scientific articles, PROMED catalogue for line of investigations of the researchers and their affialiations, IMPI databases for patents, and for technological transfer stage was done by an interview and inquiry with enterprises that accepted answer this one.

Results and discussion

The AgNP could be the next tool for a new generation of diseases treatments (Rai et al. 2009), improving electronic devices (Li et al. 2005), coating medical instruments, and enhancing performance of several applications as sensorial detectors, electroluminescent displays and biological labels among others (Abou et al. 2010). Nevertheless, the absence of an appropriate regulation and the lack of control production can turn these promising advances into serious backwards. In this study, we follow the AgNP track, from the R&D until the commercialization sector. This outlook gives a first approach on how AgNP are inserted on the national production, in order to foresight their likely impacts as possible. The bibliometric research showed 902 scientific articles only using the keyword filters, silver and nano*. Nevertheless, excluding the scientific articles that did not cover the subject, we worked with a total of 714 research articles. Up to this time, Mexico is ranked in the 24th position of 100 countries of published articles, representing the 1.15% from 78,063 total papers over the World; with a marked increase since 2013 (Fig. 1). Furthermore, significant collaborations (13.3%) with American institutions were observed, as well as, an elevated attention of researchers at Institutions in the North of the country. San Luis Potosi, Nuevo León, Baja California, Sonora, and Jalisco all of these states are located in the North of Mexico, with a clear trending on material sciences, chemistry, physics, and engineering areas (Fig. 2), which show in the first instance, the orientation of the investigation generated at the country.

Fig. 1

Source: Web of Science Core Collection Data, until September, 2019

The research articles on AgNP. a World comparison for the 2009–2019 period. b Behaviour of articles published in Mexico. c Mexican collaboration with others countries. d Articles published by Mexican institutions

Fig. 2

Source: Web of Science Core Collection Data, until September, 2019

a The most developed areas in AgNP. b The most published authors on AgNP topics in Mexico for the 2009–2019 period

Furthermore, an analysis of the authors with more publications was executed, in order to locate the most published areas and the leadership Institutions. From the top 10 authors, half belong to the UNAM, nevertheless two authors from the “Universidad Autónoma de San Luis Potosi” (UASLP) leads the number of publications (Fig. 2).

In order to reach a broad spectrum over the type of research done, the full articles were downloaded and processed. It was found that 84% of the studies focus on the synthesis and characterization of AgNP, using mainly, different chemical reductions and Transmission Electron Microscopy (TEM) for characterization (Fig. 3). The synthesis is carried out by chemical methods using reducing compounds potentially hazard like sodium borohydride (León-Silva et al. 2016). Additionally, several articles suggested a high environmental exposure followed by human exposure, mainly through oral and dermal path (Fig. 4). Almost 57% of the total search done (714 articles) suggested a beneficial impact. However, only less than a half, i.e., 27.6% (144 articles) advised a risk, meanwhile, 10.6% (76 articles) indicated a human damage with concerns related to the generation of reactive oxygen species (ROS), inflammatory effects or mitochondrial damage. Furthermore, it is noteworthy that only 25 articles (3.5%) suggested an environmental damage recommending further studies and more in-depth investigations on their impacts. In the other hand, the primary applications of AgNP were focused on prevent infections and the development of sensors for diagnosis, followed by optical and biomedical applications (Fig. 5).

Fig. 3

Source: Web of Science Core Collection Data, until September, 2019

a The most used synthesis techniques. b The most used characterization techniques

Fig. 4

Source: Web of Science Core Collection Data, until September, 2019

a Elements used with AgNP. b Type of chemical reductors used in AgNP synthesis. c Elements exposed to AgNP. d AgNP principal route of exposure

Fig. 5

Source: Web of Science Core Collection Data, until September, 2019

a Principal research effects investigated over AgNP in Mexico. b Main applications of AgNP in Mexico.

Thirdly, a register of the Academic groups that research AgNP was elaborated, finding 20 Academic groups, which represent the 11.5% from a total of 174 Academic groups that work with NT in the country. These groups incorporate 17 different institutions working on Materials Science and Physic-chemistry areas, restating the bibliometric analysis of top research areas (Table 4).

Table 4 Main academic group researching AgNP topics in Mexico

Subsequently, with prior information and with the intention of understanding the development of the AgNP research communities in Mexico; a co-author network was done. With this procedure, we illustrate the institutional distribution, the collaboration between researchers and the existing communities in the area. On Figs. 6 and 7, the size of each node determines the frequency of their participation in articles, the edges represent co-author relationships, and the colours of each node represent the community to which they belong (Fig. 6), or the affiliation institution of each researcher (Fig. 7).

Fig. 6

AgNP co-author network communities. *Displaying communities above 4% from total. Designed with WoS data and Gephi software

Fig. 7

AgNP co-author network by Institution. *Displaying Institutions above 2% from total. Designed with WoS data and Gephi software

The co-author network shows more than 1300 researchers working on AgNP. In which the UNAM, is the institution with the highest record of researchers, with more than 200. In the second place, the UASLP with 78 researchers was found, and the UANL, with 70 elements in third place. The most growing community (in yellow) had 107 researchers in which most of its members are developing, the Material Science area. Followed by Engineering and Polymers area with 87 researchers (in green), and 77 elements specialised on Physical-chemistry field. Additionally, Table 5 shows the top 10 researchers sorted according to the Eigenvector Centrality method, where the eigenvector measures the impact of a person involved in a social network. However, this should not be misunderstood as the unique and definitive way to measure the importance of a researcher; inasmuch as several parameters must be needed to be considered for a full sight.

Table 5 Author’s centrality, affiliation institution, developing area, and number of co-authors

Through this analysis of published data, we elucidate that the major development of AgNP in the country focuses on the exploitation of its antibacterial and antifungal properties for coatings and biomedical appliances, from basic science projects and with low interest on the environmental impact.

The next step on this AgNP outlook implies the intellectual property. In this section, it was done an advanced research in the IMPI’s database, searching through several key filters as: ‘nanopartículas de plata’, ‘nanomaterial plata’, ‘nano plata’, ‘nanoplata’, and ‘nano silver’. It was found seventeen patents; eight of them belong to six private companies (Daewoo, Kimberly-Clark, Novartis, American Silver, Nanoholdings, and Saeco). Two patents belong to two international academic institutions (Indian Institute of Technology and Northwest University) (Fig. 8). The last seven belongs to national academic institutions (Universidad Autónoma de Nuevo León [UANL], Centro de Investigación en Química Aplicada [CIQA], Universidad de Sonora [UNISON], Universidad Nacional Autónoma de México [UNAM], and Centro de Innovación Aplicada en Tecnologías Competitivas [CIATEC]) it should be noted, that academic patents were related to synthesis or production methods. Meanwhile, the rest of the patents describe application products like household appliances with antimicrobial coatings. Additionally, it is notorious that the patenting process has had an increase from 2016 until now, since in this 3-year period, the patents granted have been increased to twice the total obtained from 2009 to 2019.

Fig. 8

Source: IMPI database until September, 2019

Analysis of AgNP patents in Mexico according to IMPI’s database. a AgNP patent holders. b Trademark holders. c Mexican institutions patent applications. d Companies patent applications

Furthermore, it was also detected twelve trademarks from five companies (Golden Silver, Agrovit, Vitasoil, Conair, and Samsung) declaring AgNP in household products such as fridges, hair straighteners, dryers, brushes, soil remediation, and dietary supplements. Finally, eighty-four patent applications were traced; six of them were abandoned or denied, thirty-three were distributed in several applications belonging to twenty-five different companies, from this group eight request of patents are from Mexican enterprises (Bionag, A.G. Mexicana de Nanotecnología, Versatilidad de Plásticos, Kaisha Consultoría, La Joya, Versaplas, and Nanomateriales), thirty-eight requests become from Mexican Academic Institutions, while the remaining seven are from private applicants. In addition, fifteen applications from the academic group requests, seek patent an application or product. However, the other twenty-three requests try to patent a synthesis method or process. Finally, it should be noted, that we found two patent applications belonging to an American Institutions (Northwest University and Texas University) (Fig. 8). Purposely, the United States is the country that most collaborate with Mexico (Lancho-Barrantes and Cantú-Ortiz 2019).

It is noteworthy that in three of the Mexican companies (Bionag, Versaplas, and Nanomateriales) the registered inventors are also leading researchers. These are a good example where they have successfully managed the technological transfer from R&D into commercial products. The final step is the commercialization of AgNP products. Twenty-four companies that announced to use AgNP on their products or production processes were identified (Table 6). Thirteen transnational enterprises as Conair, Croc, Andis, Bayer, Kemet, Sony, Daewoo, Samsung, Whirpool, Mabe, Phiten, Vitasoil, and Vacman, manufacture products as razors, hair straighteners, dryers, brushes, chemical coatings, fridges, washing machines, camera lens, vacuums, and nanocapacitors. The remaining eleven were national companies, selling antibacterial solutions, cleaning and purifying products, and shoe inserts. These companies are located in the North of the country such as States of Baja California, Nuevo León, and Guanajuato, mainly. Also, two of them have their headquarters in Mexico City.

Table 6 Selling products in Mexico that announced to contain AgNP

Furthermore, during research on World Wide Web, it was found that ten companies are developing projects in Mexico that include AgNP. Products for coatings, cosmetics, textiles, polymers, paintings, prosthesis, and nutritional suppliers will be produced using AgNP; all of these companies have manufacturing plants located in the North and Centre of the country, mainly (Table 7). It should be considered that this results were obtain with the information achieved by companies declaring using AgNP, however, it is extremely difficult to list all companies that use AgNP due in part the difficulty of tracking the total companies in Mexico at any given time and due the lack of a legal structure, labelling or registered nano-products on the market in order to identify them.

Table 7 Companies developing projects with nanoparticles of silver in Mexico

The previous results present a first approach to the AgNP status in Mexico; ranging from R&D to commercialization products. This outlook denotes a vast capacity of basic research regarding silver nanoparticles, suggesting the opportunity for developed more applications. In addition, there was noted an increase of Mexican patents, applications, and registered trademarks since 2016 as well as Mexican companies trading products. Finally, this study offers a first approach to the scientific and commercial transfer of AgNP technology, in order to infer and taking decisions, and make projections at different terms, according to this information. This country has a high capability to do research and development, nevertheless, still requires consolidating their relationship with the industry to generate a propitious environment to scale up the production and commercialization of these technologies in national and international markets and strengthen collaboration with other countries.

Conclusions

Firstly, there is a lacking of regulatory policy and an absence of a suitable technological transfer infrastructure, that cause a slow growth in this area. Additionally, all, articles (714) published shown results where the environmental impact was put aside, without concerning any of their impacts; so, the long-term environmental effect studies are needed to demonstrate the real accumulation, permanency, and disposal of the AgNP after their use, on their different environments.

Second, academic institutions are focus on basic science, meanwhile transnational companies are introducing consumer products from their countries and others, which certainly delay the growth of the national industry. Nevertheless, we found nine national industries versus twenty-three international companies, all of them showed products, projects or patents registered in Mexico. This is done without any regulation or legal obligation to label their products containing any kind of nanotechnology, and also, we found there is not either a record of nanotech products or even, a catalogue of products or companies.

Third, results suggest opportunities for development, application, and collaboration on NP and NM fields, even for legislation and regulation fields.

Finally, Mexico has a good capability to do research and development, nevertheless, is required consolidating their relationship with the industry in order to generate a propitious environment to scale up the production and commercialization of these technologies in national and international markets, and strengthen collaboration with other countries.