The Use of Biosensor as a New Trend in Cancer: Bibliometric Analysis from 2007 to 2017

Nanotechnology is a multidisciplinary field that covers large areas of chemistry, physics, and biology as well as engineering. The application in medicine for diagnosis, prevention, and treatment of diseases, has become known as nanomedicine and is now an excellent tool for new nanotechnological applications, such as the use of biosensors. This study aimed to analyze bibliometrics related to applications in biosensors and the relative importance of these publications in cancer. The search base for articles was Google Scholar, due to the higher coverage of articles published in comparison to other databases of scientific publications, such as Pubmed and Science Direct. The obtained results showed that there was a decrease in the number of publications referring to cancer at the last decade (2007-2017), but there was an increase in the number of publications regarding the use of biosensors, showing an interest and tendency using new technologies for clinical diagnosis. Nanotechnology is a promising tool for the development of new diagnostic methods and its growth for the next decades is undeniable, including biosensors.


Introduction
Nanotechnology is a multidisciplinary science, encompassing the areas of engineering, biology, chemistry and physics, being more and more applied in medicine and pharmacy [1][2][3][4][5][6]. Nanotechnology's applications range from drug release studies to the use of biosensors as a tool for the early diagnosis in several diseases, as well as the treatment of drugs and antibodies in target systems in diseases such as cancer [7][8][9][10].
The interest of the use of biosensors for early detection in cancer using nanotechnology is of great importance for early clinical diagnosis and consequently to contribute to the reduction of mortality as well as to the improvement of the quality of life of the population [124][125][126][127][128][129][130][131][132][133].
Cancer is the second leading cause of death worldwide [134][135][136][137][138][139][140][141][142][143][144]. Thus, the use of biosensors has become a promising tool for early diagnosis, since the risk of metastasis is a critical point in the development of the disease, rapidly causing the death of the individual. Because tumor cells are present at shallow levels in peripheral blood, they can be detected in patients with advanced tumors with or without metastasis. Thus, the present study analyzed bibliometrics related to applications in biosensors and the relative importance of these publications in cancer. The obtained results showed that there was a decrease in the number of publications referring to cancer at the last decade (2007-2017), but there was an increase in the number of publications regarding the use of biosensors, showing an interest and tendency using new technologies for clinical diagnosis Search bases such as Scopus®, Web of Science®, and Compendex® have their metrics, and when we join these three databases in a single search, there may be discrepancies in citation numbers, as well as articles contained in all of them [145]. Google Scholar® will fetch all articles using the same metric. For the bibliometrics of scientific productions in the last decade, keywords were used for the use of biosensors and their applications in cancer in specific periods from 2007 to 2017. The applications in biosensors used were diagnostic, bio-detection, biomarker, prevention, biomaterial, nanoparticles, graphene, tattoos and Point-of-care (POC).
To analyze the impact of nanotechnology with biosensors on the scientific production of cancer in the last decade, a calculation was performed aiming to obtain the relative importance based on the publications of biosensors and their applications in cancer and the total number of scientific productions in cancer (Table 1). From the relative importance of publications in biosensors for each application in cancer followed year by year, a tendency curve was prepared using an exponential model for a higher sensitivity of the obtained data, as well as the equation and value of R² (coefficient of determination) for a better fit of the statistical model. The value of R²≥0.9 (90%) was used as the reliability criterion of the results obtained through bibliometrics analysis.

Results and Discussion
In the last decade, the publications about cancer suffered a decrease. For instance, 2017 produced around 144K scientific publications, whereas in 2007 more than 1.1 million publications were produced. This observed decrease in bibliometrics during the last decade is shown in Table 2 and Figure 1. Regarding cancer, in 2007, around 0.18% of cancer publications were associated with the use of biosensors for diagnosis and in 2017, this number increased to 6.62% of total cancer publications, as shown in Table 3. Figure   2 shows the Tendency Curve for cancer diagnosis, allowing for inferring an exponential increase with R² equals to 0.9301 (93%).         In cancer, the relative importance of publications in biosensors and bio-detection was of 0.013% in 2007. Over the past few years, Relative Importance has increased. In 2017, its approximate value was 0.47%, showing that research on biosensor tumor markers using biosensors are increasing. This increase can be observed in Table 4 and Figure 4. Figure 5 shows the increase in the number of publications in biodetection in the last decade. The relative importance of biosensor and biomarker publications in cancer has increased in the last decade. In 2007, 0.078% of the publications in tuberculosis were directly related to biosensors and biomarker; in 2017, this value was of 4.49%. Table 5 and Figure 6 show the treated data. Figure 7 shows the number of publications in the last decade of the use of biosensors as a biomarker in cancer.

Relative Importance in Biodetection
Year   The Relative Importance of biosensor publications and cancer prevention has increased in the last decade. In 2007, 0.11% of cancer publications were directly related to biosensors and prevention; in 2017, this value was of 3.86%. Table 6 and Figure 8 show the treated data. Figure 9 shows the number of publications of biosensor and prevention in cancer in the last decade   Relative Importance in Prevention (%)

B IO D E T E C T IO N
Year

Publication in Prevention
Year Figure 10: The Relative Importance and Tendency Curve of biosensor and biomaterial in cancer in the last decade. Relative Importance in Biomaterial (%) Year  The relative importance of biosensor and biomaterial publications in cancer has increased in the last decade. In 2007, 0.11% of cancer publications were directly related to biosensors and biomaterials; in 2017, this value was of 4.93%. Table 7 shows these values during the last decade, while Figure 10 presents the tendency line, the value of R², as well as the Relative Importance.

B IO M A T E R IA L
The number of publications about biosensors and biomaterials in cancer has increased over the last decade, as can be seen in Figure  11. In 2007, there were 1.39K publications; in 2017, the number increased reaching 7.10K publications. The relative importance of publications of biosensors and nanoparticles in cancer has increased in the last decade. In 2007, 0.13% of cancer publications were directly related to biosensors and nanoparticles; in 2017, this value was of 7.77%. Table 8 and Figure 12 show the treated data. The number of publications on biosensors and nanoparticles in cancer has increased over the last decade, as can be seen in Figure 13. In 2007, the number of publications was equal to 1.69K publications; in 2017, the number reached 11.20K publications.

N° of Publication in Biomaterial
Publication in Biomaterial Year Figure 12: The Relative Importance and Tendency Curve of the biosensor using nanoparticles in cancer in the last decade.

N° of Publication in Nanoparticles
The relative importance of publications of biosensors and graphene in cancer has increased in the last decade. In 2007, 0.01% of cancer publications were directly related to biosensors and graphene; in 2017, this value was of 3.99%. Table 9 and Figure 14 show the treated data. The Relative Importance of biosensor and tattoos publications on cancer has increased in the last decade. In 2007, 0.001% of cancer publications were directly related to biosensors and tattoos; in 2017, this value was of 0.07%. Table 10 shows these values during the last decade; and in Figure 15 it is possible to observe the tendency line, the value of R², as well as the Relative Importance. The number of publications on biosensors and tattoos in cancer has increased over the last decade, as can be seen in Figure 16.  Relative Importance in Graphene(%) Year   Year    The relative importance of biosensor and point-of-care (POC) publications in cancer has increased in the last decade. In 2007, 0.02% of cancer publications were directly related to biosensors and POCs; in 2017, this value was of 1.77%. Table 11 shows these values during the last decade; and in Figure 17 it is possible to observe the tendency line, the value of R², as well as Relative Importance. The number of publications on biosensors and Pointof-care in cancer has increased over the last decade, as can be seen in Figure 18.  Relative Importance in point of care (%)

T A T T O O S
Year

Publication of Point of Care
Year Figure 19: Comparison of the number of biosensor publications in the cancer applications that this study considered. Figure 19 shows a comparison of the number of biosensor publications in the cancer applications that this study considered. Despite the more significant number of publications being diagnosed, it can be observed that the number of publications in the year 2017 using nanoparticles in cancer was higher than in diagnosis. The second highest number of applications was diagnosed, followed by biomaterial, biomarker, prevention, graphene, point-of-care, bio-detection, and tattoo, respectively. Some factors may have contributed to the decline of bibliometrics in cancer. One such factor was the global crisis that occurred in the period from 2008 to 2013, which directly affected investment in R & D in several countries around the world, as shown in a study by OECD [146].
Although the fall in investment may have directly affected cancer research, it has been observed that concerning nanotechnology, the bibliometrics in cancer biosensors have increased considerably, evidencing a trend in new technologies applied to medicine. Figure 20 shows the values of the relative importance of biosensor applications in cancer. As can be observed, the use of nanoparticles in the year 2016 and 2017 has become the largest of all applications, followed by diagnosis, biomaterial, biomarker, graphene, prevention, point-of-care, bio-detection, and tattoos. As it was shown throughout this work, all the curves of tendency had behavior that corresponds to the increase of the publications using biosensors in cancer, confirming, thus, a tendency in the use of the same one.