# Visualizing the Knowledge Domain of Nanoparticle Drug Delivery Technologies: A Scientometric Review
## 4 Bibliographic Landscape
### Identification and Interpretation of Clusters  
We used _CiteSpace_ to explore research patterns and emerging trends in the body of knowledge in terms of key clusters of articles. Figure 2 shows clusters labeled with title terms. The size of a cluster's label is proportional to the size of the cluster. In this instance, there are total 55 clusters in the network. To characterize the nature of a cluster, _CiteSpace_ can extract noun phrases from the titles of articles that cited the cluster based on three \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Cited** & **Title** & **Author** & **Year** &
\begin{tabular}{c} **Betweenness** \\ **Centrality** \\ \end{tabular} & **Journal** \\
1014 & \
\begin{tabular}{c} Nanocarriers as an emerging \\ platform for cancer therapy \\ \end{tabular} & [PERSON] _et al._ & 2007 & 0.00 &
\begin{tabular}{c} Nature \\ Nanotechnology \\ \end{tabular} \\ \hline
829 & \
\begin{tabular}{c} Synthesis and surface engineering \\ of iron oxide nanoparticles for \\ biomedical applications \\ \end{tabular} &
\begin{tabular}{c} Gupta and \\ Gupta \\ \end{tabular} & 2005 & 0.02 & Biomaterials \\ \hline
764 &
\begin{tabular}{c} Multifunctional inorganic nanoparticles \\ for imaging, targeting, and drug delivery \\ \end{tabular} & [PERSON] _et al._ & 2008 & 0.00 & ACS Nano \\ \hline
755 & \
\begin{tabular}{c} Superparamagnetic nanoparticles for \\ biomedical applications: possibilities and \\ limitations of a new drug delivery system \\ \end{tabular} & [PERSON] _et al._ & 2005 & 0.01 &
\begin{tabular}{c} Journal of \\ Magnetism and \\ Magnetic Materials \\ \end{tabular} \\ \hline
712 & \
\begin{tabular}{c} Tumor vascular permeability and the \\ EPR effect in macromolecular \\ therapeutics: a review \\ \end{tabular} & [PERSON] _et al._ & 2000 & 0.08 &
\begin{tabular}{c} Journal of \\ Controlled Release \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Five critical articles in nanoparticle drug delivery technologies. Figure 2: Clusters visualization based on a document co-citation network. specialized metrics--TF*IDF, log-likelihood tests (LLR) and mutual information tests (MI). LLR usually gives the best result in terms of the uniqueness and coverage of themes associated with a cluster. Table 2 details the top \(11\) clusters in rank order. As shown in Figure 2, _gold nanoparticle_ and _magnetic nanoparticle_ are the two largest clusters. _Microcrystal_ and _mesoporous silica nanoparticle_ are the two youngest clusters, and _glucomanuman-chitosan nanoparticle_ is the oldest cluster. The values of the silhouettes for each cluster are greater than 0.5, suggesting robust and meaningful results. The largest cluster, _gold nanoparticle_ (#0), consists of 55 members. The three most active citers in this cluster are [PERSON] _et al._[20], [PERSON] and [PERSON] [21], and [PERSON] [22]. According to the titles of these citers in this cluster, research works related to gold nanoparticle shape a foundation of the knowledge domain. Researchers interested in gold nanoparticle are particularly concerned with near-infrared quantum dot, toxicity, and biomaterial-based technologies. Not surprisingly, this cluster covers a range of interests, reflecting the interdisciplinary nature of NDDT and their use. The second largest cluster (#1) in this knowledge domain, _magnetic nanoparticle_, has 53 member articles and an average publication year of 2003. The three most active citers to this cluster are [PERSON] _et al._[23],[PERSON] _et al._[24], and [PERSON] _et al._[25] accordingly. Because of their remarkable magnetic properties and biologically comparable sizes, these magnetic nanoparticles are very beneficial for biomedical applications [23]. In addition, these magnetic nanoparticles can also respond resonantly to an alternating magnetic field and function as a heater, offering a promising therapeutic solution by magnetic fluid hyperthermia [25].