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With the advance of science and technology, nanomaterials have been seen in various biomedical applications, including molecular labeling and tracking, DNA/RNA/proteins probing, drug delivery and therapies via techniques of biocujugation, tumor or tissue targeting, peptide drug discovery, pathogenic intervention as well as biomedical imaging.

Introduction

Nanotechnology is the study of materials in the nanoscale and involves multiple disciplines by its nature. Nanotechnology has made a significant stride in recent two decades in various industries. Numerous nanomaterials are devised for biomedical applications which include intracellular tracking and labeling, tumor or tissue targeting, pharmaceutical therapies, gene detection and hybridization, pathogenic inhibiting, and medical instrument coating for disinfections. High photostability and quantum yield of fluorescent nanoparticles are ideal for long-term monitoring of molecular events in living organisms.

Fluorescent nanoparticles

Fluorescent molecules play a pivotal role in optical imaging of life science research and biomedical applications. While epitope mapping is also a way to discover and develop diagnostic and therapeutic molecules, fluorescent probes can be more widely used to analyze proteins, hormones, and viral antigens; detect RNA and DNA; or identify organelles, tissues, specific proteins, or tumors via antibody conjugation. Gold/ Silver nanoparticles conjugation are just one kind.

Biocompatible enhancer for nanoparticle delivery

Most organic and inorganic nanomaterials are either hydrophobic or water-insoluble, which means they are difficult to be delivered into cells or organisms. To circumvent this issue, several strategies have been developed, among them are cell-penetrating peptides (CPPs). CPPs (a.k.a., PTDs) are proteins that are capable of penetrating cell membranes. In recent decades, they have attracted immense popularity in delivering bioactive macromolecules, genes, and drugs due to their effect intracellular translocation. CPP-mediated direct membrane location presents an excellent option for delivering drugs and other bioactive molecules.

CPPs can interact with cargoes in a covalent, noncovalent, or covalent and noncovalent protein transduction (CNPT) manner. Cargoes are optional, including proteins, siRNA, DNA, and semiconductors QDs. CPP-mediated cellular uptake can be found from prokaryotic to eukaryotic organisms including mammalian cells, aquatic microorganism, yeasts, insect cells, mice dermis, plant tissue, Gram-negative and Gram-positive bacteria, and archaea.

Cell viability in mammalian cells

In this study, human bronchoalveolar carcinoma A549 cells were used as a model cell line to investigate CPP-mediated uptake of inorganic fluorescent nanoparticles. Collectively, semiconductor fluorescent nanoparticles and their CPP-modified complexes did not reduce cell viability.

Survival rate in rotifers

Rotifers are non-arthropoda, metazoan aquatic invertebrates with a completed digestive systems. They form the basis of the microzooplankton community in the plankton food web and link the energy flow to higher organisms. Recently, a growing number of studies considers rotifers as an indicator of marine pollution and toxicity of plastic nanoparticles, as well as a model species for pharma-ceutical and toxicological studies. Therefore, to investigate potential cytotoxicity of CPP-associated quantum dots on rotifers, the MTT assay was performed. Overally speaking, CPP-mediated cellular entry of quantum dots resulted in relatively harmless in rotifers.

Hypotoxicity shown in prokaryotic organisms

Microorganisms are regarded as a vital members in the ecosystem as they play an important role in the elements and energy transforming, natural recycling, and environmental balancing of living materials. Prokaryotic organisms are major microorganisms which include bacteria and archaea. In this study, scherichia coli DH5α (Gram-negative bacteria), Arthrobacter ilicis D50–1 (Gram-positive bacteria), E, and Thermus aquaticus (archaea) were studied for protein transduction and cytotoxicity. They were treated with Cd-core green semiconductor nanoparticles. Toxicological studies of nanomaterials on prokaryotic organisms are important. Bactericidal nanomaterials can affect nonpathogenic bacteria leading to imbalance of a microbiome community and, to the greatest extent, ecological disasters. The research result indicated that Cd-core nanoparticles did not cause lethal effect to prokaryotic organisms. Hence, it could be reasonably ratiocinated that fluorescent nanoparticles applied in bioimaging and biotechnologies might not provoke natural imbalance and environmental problems.

Conclusion

In this article, applications and safety issues of various fluorescent nanoparticles are discussed. The cellular entry of particles of interest can be facilitated by CPPs. And the good news is that the particles did not produce lethal effects in mammalian cells, archaea, rotifers, Gram-positive bacte-ria, and Gram-negative bacteria. The outcome from assessing nanoparticle safety in mammalian cells suggests their potential medical applications. Hypotoxicity in rotifers and prokaryotes infers their environmental safety and eco-friendliness. In summary, these fluorescent nanoparticles and their CPP-modified complexes can be potent tools in various biological, environmental, and medical applications in the future.