# Nanomaterial Databases: Data Sources for Promoting Design and Risk Assessment of Nanomaterials
## 3 Comparative Analysis of the Databases
Figure 2: Number of carbon-based nanomaterials (z-axis) of four shape types (depicted in different colors and marked at the \(y\)-axis) in the seven nanomaterial databases indicated on the \(x\)-axis. The quantities of nanomaterials for each type of structural characterization in the seven databases are summarized in Figure 3. Aspect ratio/shape information is provided in all the seven databases. Except NIL, the other six databases cover coating/shell information and size-related information, such as size or size distribution. However, NIL has diameter information, which is not included in other databases. Surface area information is stated in the databases of eNanoMapper, NR, NKB and NIL. The purity property is only mentioned in caNanoLab and NR. It is noteworthy that caNanoLab and NKB also have physical state information. For functional group information, it is provided only by NBIK, and crystallite and grain phase information is included only in the eNanoMapper database. The quantities of nanomaterials for each type of physicochemical property in the seven databases are summarized in Figure 4. It is worth mentioning that physicochemical properties are sparsely scattered in the seven databases. Most of the physicochemical properties are included in only one database: electrophoretic mobility and energy band gap in NKB; aggregation, stability, and surface reactivity in NR; density, localized surface plasmon resonance, and saturation magnetization in eNanoMapper; Log P in PubVINAS; and relaxivity in caNanoLab. Molecular weights are provided in both caNanoLab and NKB for a small number of nanomaterials. Solubility data are included in caNanoLab, eNanoMapper, and NR for a small portion of the nanomaterials. Surface charge is the physicochemical property that is included for most the nanomaterials in five of the seven databases (eNanoMapper, NR, NBIK, NKB, and PubVINAS). It is noteworthy that caNanoLab also has surface charge. However, users need to zoom in on the record for each nanomaterial to find surface charge. It is hard to find the number of nanomaterials that have surface charges. Therefore, caNanoLab was not included in the surface charge discussion as shown in Figure 4.  
Figure 3: Number of nanomaterials (\(z\)-axis) with structure characterizations (indicated on the \(x\)-axis) in the seven databases (depicted in different colors and marked on the \(y\)-axis). The biological properties were also compared among the seven databases. It is noted that caNanoLab and eNanoMapper databases have more biological data points than the other databases, while NIL does not have biological data in a searchable field. Thus, it is not included in the subsequent comparison. The quantities of nanomaterials for 23 common types of biological characterizations in six databases are shown in Figure 5. Similar to the physicochemical properties, the biological data are very sparse in the six databases. It is noticeable that caNanoLab and eNanomapper not only contain more nanomaterials than the other databases (Table 2), but also include more biological data than the other databases. Interestingly, PubVINAS also has rich information of biological characterizations. The biological data contained in the other three databases (NR, NBIK, NKB) are in small amounts with very few types. Figure 4: Number of nanomaterials (\(z\)-axis) with physicochemical properties (indicated on the \(x\)-axis) in the seven databases (depicted in different colors and marked on the \(y\)-axis). Figure 5: Number of nanomaterials (\(z\)-axis) with biological activity data (indicated on the \(x\)-axis) in the six databases (depicted in different colors and marked on the \(y\)-axis). The five most basic database functionalities (browse, search, filter, data export, and data upload) for the seven nanomaterial databases are summarized in Table 3. All seven databases provide browse function for users to examine the database content.