# Visualizing the Knowledge Domain of Nanoparticle Drug Delivery Technologies: A Scientometric Review
## 4 Bibliographic Landscape
### Identification and Interpretation of Clusters
In recent years, the synthesis, design, and fabrication of multifunctional magnetic nanoparticles for biomedical applications has become one of the most active research areas in this knowledge domain [24]. As shown in Figures 1 and 2 this cluster has the top ranked burst item--[PERSON] _et al._[18] among all clusters, with bursts of 61.86. Thus, the magnetic nanoparticle cluster is essential to the literature represented by the datasets. The third largest cluster (#2) is _oral delivery_ which has 51 member articles and an average publication year of 2001. The three most active citers in this cluster are [PERSON] _et al._[26], [PERSON] _et al._[27], and [PERSON] _et al._[28] accordingly. According to the titles of these citers in this cluster, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**ID** & **Size** & **Silhouette** & \
\begin{tabular}{c} **Label** \\ **(TF*IDF)** \\ \end{tabular} & **Label (LLR)** & **Label (MI)** &
\begin{tabular}{c} **Mean** \\ **(Cited Year)** \\ \end{tabular} \\ \hline
0 & 55 & 0.789 & nano & gold nanoparticle &
\begin{tabular}{c} biomaterial-based \\ technologies \\ \end{tabular} & 2003 \\ \hline
1 & 53 & 0.853 & ion & magnetic nanoparticle & behavior & 2003 \\ \hline
2 & 51 & 0.776 & nano & oral delivery & general strategy & 2001 \\ \hline
3 & 48 & 0.933 & silica & mesoporous silica & anticancer drug & 2007 \\  & & & & nanoparticle & delivery system & 2003 \\ \hline
4 & 46 & 0.704 & nano & nanoparticle & drug discovery & 2003 \\ \hline
5 & 42 & 0.811 & nano & polymeric micelle & nanofibrous scaffold & 2001 \\ \hline
6 & 23 & 0.890 & nano & mesoporous silica &
\begin{tabular}{c} \\ nanoparticle \\ \end{tabular} & ouzo region & 2002 \\ \hline
7 & 13 & 0.972 & upconversion & microcrystal & drug-delivery system & 2010 \\ \hline
8 & 8 & 1.000 & \
\begin{tabular}{c} plaque \\ angiogenesis \\ \end{tabular} &
\begin{tabular}{c} nanomedicine \\ strategies \\ \end{tabular} & mechanism & 2002 \\ \hline
9 & 8 & 0.954 & nano &
\begin{tabular}{c} nanotechnology-based \\ drug delivery \\ \end{tabular} & drug-delivery system & 2000 \\ \hline
10 & 5 & 0.998 &
\begin{tabular}{c} carboxymethyl \\ konjac \\ \end{tabular} & glucomannan-chitosan nanoparticle & drug delivery & 1994 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Top-ranked clusters in nanoparticle drug delivery technologies. nanometric-sized drug delivery systems are being extensively studied and provide promising potential for oral drug delivery. Researchers interested in oral delivery focus particularly on how technological solutions can enhance the bioavailability or the targeting of anticancer drug after oral administration. There are other clusters worth mentioning. For example, the cluster (#3) for _mesoporous silica nanoparticle_ consists of 48 member articles and an average publication year of 2007. According to the major citing articles [29; 30], it is not surprising that previous advances push _mesoporous silica nanoparticle_ to the research forefront of drug delivery development. Another major cluster corresponds to the terms _polymeric micelle_. In most instances, polymeric micelles play a significant role in the advancement of NDDT by providing controlled release of therapeutic agents in constant doses over long periods [31; 32]. Thus, _polymeric micelle_ has become a substantive knowledge domain in NDDT research field. Finally, the term _microcrystal_ also represents a cluster which has 13 member articles and an average publication year of 2010. This cluster is the newest one in which the three most active citers in this cluster are [PERSON] and [PERSON] [33], [PERSON] _et al._[34], and [PERSON] _et al._[35] accordingly. Dramatic efforts have been dedicated to the chemical synthesis of rare earth fluoride nano-/microcrystals with uniform size and shapes [33]. Hence, research works related to _microcrystal_ reflect the recent knowledge domain in NDDT research field.