KeywordsCellular Uptake Size Exclusion Chromatography Isothermal Titration Calorimetry Biological Environment Human Epidermal Keratinocytes
Nanoparticle–biocorona: a layer(s) of biomolecules that adsorbs to the surface of a nanoparticle in a biological environment.
Methods to Evaluate Coronal Structure and Composition
The evaluation of the nanoparticle–biocorona typically is performed by introducing a nanoparticle into a biological environment or by collecting samples such as serum, plasma, gastrointestinal fluid, or alveolar lavage fluid, which represent the in vivo environment. Following introduction into a biological environment, nanoparticles are often isolated for analysis through centrifugation or size exclusion chromatography. The structure and properties of the biocorona are evaluated by assessments of biocoronal thickness, charge, strength of protein interactions, and protein conformational changes. The thickness of the biocorona on the surface of the nanoparticle can be studied through the use of dynamic light scattering, size exclusion chromatography, differential centrifugal sedimentation, and/or transmission electron microscopy. Alterations in surface charge or zeta potential can be evaluated by microelectrophoresis. The strength of protein interactions can be studied through the use of isothermal titration calorimetry and surface plasmon resonance, whereas circular dichroism and Fourier-transform spectroscopy and computational modeling are often used to determine changes in protein structure due to association with the nanoparticle. Evaluation of the compositional biomolecular content of the biocorona is performed by isolating biomolecules from the surface of the nanoparticle and utilizing SDS-PAGE and/or liquid chromatography–tandem mass spectrometry for the identification and quantification of individual components. Removal of the “hard” corona for biomolecule identification is difficult due to the strong association between the biomolecules and the nanoparticle, whereas the “soft” corona can easily be lost during processing due to its dynamic nature and weak interactions.
Directing Protein Adsorption for Nanomedicine Targeting
The field of nanomedicine is beginning to utilize the nanoparticle–biocorona to increase the targeting capability of nanoparticles for drug delivery. Typically, the formation of the biocorona has been associated with a decrease in cellular uptake; however, biocoronas formed of specific ligands to direct nanoparticles to particular receptors have shown promise under in vitro experimentation. In contrast, the biocorona may have unintended consequences on nanoparticle delivery. For example, the enhanced targeting ability of nanoparticles with a transferrin biocorona was lost in vivo due to the addition of the endogenous biocorona . The complexity of the biocorona as it pertains to nanoparticle cellular uptake will influence the targeting of nanomedicines. It has been demonstrated that the association of a specific protein with nanoparticles of differing size and surface coatings can have vastly different effects on cellular uptake, thereby modifying the capacity to effectively target nanotherapeutics. For example, the formulation of an IgG biocorona on 20 nm silica-coated silver nanoparticles increases cellular uptake in human epidermal keratinocytes. In contrast, an IgG biocorona on 110 nm silica-coated silver nanoparticles had no effect on uptake, whereas cellular uptake was reduced by changing the surface coating to citrate on the 110 nm silver nanoparticle with an IgG biocorona . Instead of preloading the biocorona onto nanoparticles, it may be more feasible to synthesize nanoparticles with specific physicochemical characteristics, which allow for the enrichment of certain biomolecules, resulting in a biocorona that facilitates targeted uptake. For example, PEG-coated polyhexadecyl cyanoacrylate nanoparticles have been shown to translocate from the circulation into the brain, whereas non-PEG-coated polyhexadecyl cyanoacrylate did not readily cross the blood–brain barrier . Upon investigation, this differential uptake was related to the identity of the biocorona, specifically the preferential abundance of apolipoproteins in the biocorona of PEG-coated nanoparticles.
Adverse Biological Implications of the Nanoparticle–Biocorona
The association of the biocorona with nanoparticles may result in unintended adverse biological consequences. Binding of biomolecules to the surface of nanoparticles can result in protein modifications and conformational changes, which may facilitate toxicity through activation of the immune system. Many nanoparticles have been shown to associate with biocoronas that are rich in immunoglobulins and complement proteins, which act as opsonins, facilitating uptake of nanoparticles by phagocytic cells (initiating an inflammatory response) as well as resulting in increased biodistribution to the liver and spleen. Albumin biocoronas however have been shown to increase retention time in the circulation, whereas apolipoprotein-rich biocoronas cause increased distribution into the brain. These effects demonstrate biocorona-dependent differences in the biodistribution of nanoparticles, which need to be taken into consideration for their effective utilization in biomedical applications to reduce off target effects. The addition of the biocorona can also have unintended consequences on the release of drugs from nanoparticles by not only interfering with biodistribution but also possibly causing premature or delayed release of drugs from the nanoparticle carrier .
Recent research efforts have begun evaluating how to regulate the nanoparticle–biocorona for applications in nanomedicine. However, most of the work has been done to identify the protein content of the biocorona, while less emphasis has been placed on other biomolecules such as lipids and other macromolecules. Many studies have also evaluated the influence of diverse nanoparticle physicochemical characteristics on the composition of the nanoparticle–biocorona; however, modifications in the physiological environment, which may influence the nanoparticle’s pharmacokinetic profile, still require extensive study. Further, methods and investigation of the more dynamic “soft” corona need to be performed. Most studies also focus on an individual time point of biocorona formation; however, the kinetics of the biocorona lacks sufficient analysis. Furthermore, since the “soft” corona is more dynamic with almost a constant exchange of biomolecules, studies need to be performed, addressing the impact of possible biomolecule conformational changes and oxidative modifications and the likely resulting biological consequences. Currently, the evaluation of the biocorona is limited to in vitro assessment; however, extensive in vivo analysis is needed, particularly in human populations of various underlying disease states. Ultimately, for the future development of effective nanomedicines, it will be necessary to predict the identity and the biological impact of the biocorona based on the physicochemical properties of the nanomaterial.
- 1.Salvati, A., Pitek, A.S., Monopoli, M.P., Prapainop, K., Bombelli, F.B., Hristov, D.R., Kelly, P.M., Aberg, C., Mahon, E., Dawson, K.A.: Transferrin-functionalized nanoparticles lose their targeting capabilities when a biomolecule corona adsorbs on the surface. Nat. Nanotechnol. 8(2), 137–143 (2013)CrossRefGoogle Scholar
- 3.Kim, H.R., Andrieux, K., Gil, S., Taverna, M., Chacun, H., Desmaele, D., Taran, F., Georgin, D., Couvreur, P.: Translocation of poly(ethylene glycol-co-hexadecyl)cyanoacrylate nanoparticles into rat brain endothelial cells: role of apolipoproteins in receptor-mediated endocytosis. Biomacromolecules 8(3), 793–799 (2007)CrossRefGoogle Scholar
- 4.Paula, A.J., Araujo Junior, R.T., Martinez, D.S., Paredes-Gamero, E.J., Nader, H.B., Duran, N., Justo, G.Z., Alves, O.L.: Influence of protein corona on the transport of molecules into cells by mesoporous silica nanoparticles. ACS Appl. Mater. Interfaces 5(17), 8387–8393 (2013)CrossRefGoogle Scholar