## 4 Conclusions  
The results of this study show that multi-layer graphene, also called graphene nanoplatelets (GNPs), are carbon-based nanomaterials with great potential in biomedicine and can be summarized as follows: (i) GNPs can be used in vivo at the non-toxic concentrations of 25 and 12.5 \(\mathrm{\SIUnitSymbolMicro g}\)/mL for 24 h (acute toxicity), and at 12.5 \(\mathrm{\SIUnitSymbolMicro g}\)/mL for 72 h (chronic toxicity) of exposure in _C. elegans_ model; (ii) GNPs present time-dependent cytotoxicity (EC\({}_{50}\) of 1.142 \(\mathrm{\SIUnitSymbolMicro g}\)/mL and 0.760 \(\mathrm{\SIUnitSymbolMicro g}\)/mL at 12 h and 24 h, respectively) in human keratinocyte HaCaT cells; (iii) GNPs showed significant proliferative activity at the non-cytotoxic concentrations of 0.005 and 0.01 \(\mathrm{\SIUnitSymbolMicro g}\)/mL in the keratinocytes; (iv) The gene expression analysis showed that GNPs are capable of up-regulating six of the thirteen genes (_SOD1_, _CAT_, _TGFB1_, _FN1_, _CDH1_, and _FBN_), which are involved with many important features required in biomedical fields such as wound healing and skin tissue engineering. However, more experimentation is required to provide strong scientific conclusions about the potential biomedical use of these materials in humans.  
Figure 7: Survival rate of the _Caenorhabditis elegans_ in vivo toxicity model after 24 h (acute toxicity) and 72 h (chronic toxicity) of exposure to graphene nanoplatelets (GNPs). Data are expressed as the mean \(\pm\) standard deviation of five replicates (n = 5). The results of the statistical analysis with respect to positive control and to the epidermal growth factor (EGF) are indicated in the graph: \({}^{**}\)\(p\) < 0.01; \({}^{***}\)\(p\) < 0.001, n.s: not significant.  
**Author Contributions:** Conceptualization: B.S. and A.S.-A.; methodology, validation, and formal analysis: B.S., A.T.-M., A.C.-V., M.A., J.A. and A.S.-A.; software: B.S. and A.S.-A.; investigation: B.S., A.T.-M., A.C.-V., M.A., J.A. and A.S.-A.; resources: J.A. and A.S.-A.; data curation: B.S., A.T.-M., A.C.-V., M.A., J.A. and A.S.-A.; visualization: B.S. and A.S.-A.; writing--original draft preparation: A.S.-A.; writing--review and editing: B.S., A.T.-M., A.C.-V., M.A., J.A. and A.S.-A.; supervision: [PERSON] and A.S.-A.; project administration: A.S.-A.; funding acquisition, J.A. and A.S.-A. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was supported by the Fundacion Universidad Catolica de Valencia San Vicente Martir, Grant 2020-231-006 UCV and by the Ministerio de Ciencia e Innovacion (PID2020-119333 RB-I00/ AEI/10.13039/501100011033) (awarded to A.S-A). J.A. acknowledges Universitat Jaume I for project UJI-B2019-30, Generalitat Valenciana for project AICO2020, and Ministerio de Ciencia, Innovacion y Universidades (Spain) project PGC2018- 094417-B-I00 for supporting this research financially. M.A. acknowledges Fundacao de Amparo a Pesquisa do Estado de Sao Paulo--FAPESP (FAPESP CEPID-finance code 2013/07296-2), FINEP, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico--CNPq (finance code 166281/2017-4), and CAPES (finance code 001).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data is contained within the article.  
**Acknowledgments:** The authors would like to express their gratitude to the Fundacion Universidad Catolica de Valencia San Vicente Martir, the Generalitat Valenciana, the Fundacao de Amparo a Pesquisa do Estado de Sao Paulo and to the Spanish Ministry of Science and Innovation for their financial support.  
**Conflicts of Interest:** The authors declare no conflict of interest.