**4. Nanoparticles with biomedical applications**

Nanomedicine deals with the biomedical applications of nanomaterials; in this area, nanomaterials are used creatively for the design and preparation of new forms of drug delivery, improving their precision and effectiveness due to their unique properties, or for the creation of novel formulations, sensors for early diagnosis and medical imaging contrast agents for the early detection of diseases in a minimally invasive way, with higher resolution, sensitivity, and specificity, among other uses.

Quantum dots are an example: they have unique physical characteristics, especially their size which can be controlled to tune their light emission properties; they have been used to solve problems related to the modulation of the intensity and duration of fluorescence when staining cell or tissue samples for microscopic analysis, in addition to the fact that by coating their surface they can target specific sites and allow, for example, the detection of tumors [24].

Magnetic nanoparticles are being successfully used in medical magnetic resonance imaging (MRI) as contrast agents to visualize biological structures that cannot be identified with conventional MRI, which has a major impact on diagnosis, allowing patients to receive more appropriate care in the best possible time [25].

Perhaps the greatest potential application of nanomaterials is in the design of novel drug delivery systems, in which polymeric and lipid-based nanoparticles seem to lead, although examples can be found with other nanomaterials usually PEGylated (coated with polyethylene glycol) to improve their biocompatibility; in the case of lipid nanoparticles, as they form a vesicle with a double membrane, the drug can be loaded inside the vesicle or between the lipid bilayer and be directed into a specific target by functionalizing their surface [18]. Extensive research has been done with functionalized nanoparticles to act as virucidal agents for Zika, rabies, influenza, HIV, hepatitis, papilloma, among other viral diseases. [13]. This is a promising area considering the current pandemic and the need for vaccines in short times not only to respond to SARS-Cov-2 but for emerging viral diseases to come, so having candidate nanomaterials ready to generate such vaccines is pressing.

Another area of opportunity is the development of nanoparticle-based biosensors. These are being used not only for the detection of diseases but also for the stratification of such pathologies, and even for the early detection of asymptomatic patients who would benefit from early diagnosis, for example for cancer. Among the advantages of these biosensors are their very high specificity, sometimes better than conventional biopsies, and that they are non-invasive so that sensors can be generated for routine use for screening and monitoring of drug resistance or function [26].
