The interaction mechanism between gold nanoparticles and proteins: Lysozyme, trypsin, pepsin, γ-globulin, and hemoglobin

In this study, the interaction between gold nanoparticles (AuNPs) and proteins (including lysozyme, trypsin, pepsin, γ-globulin and hemoglobin) was investigated by UV-visible absorption spectroscopy, fluorescence spectroscopy, circular dichroism (CD) spectroscopy and protein activity assay. AuNPs was synthesized using reduction of HAuCl₄ with sodium citrate. The formation of AuNPs was confirmed from the characteristic surface plasmon resonance band at 521 nm and transmission electron microscopy revealed the average particle size was about 10 nm. The results reveal that AuNPs can interact with proteins to form a "protein corona (PC)", but the protein concentration required to form a relatively stable PC is not the same. The quenching mechanism of proteins by AuNPs is arisen from static quenching. The binding constants of AuNPs with proteins are in the range from 10⁶ to 10¹⁰ L mol^-1, and the order is pepsin > γ-globulin > hemoglobin > trypsin > lysozyme at 298 K. Van der Waals forces and hydrogen bonds are the main forces for the lysozyme-AuNPs system. The interaction between trypsin/pepsin/γ-globulin/hemoglobin and AuNPs is mainly by hydrophobic interaction. The addition of AuNPs has an effect on the secondary structure of proteins as confirmed from CD spectra. The change in secondary structure of different proteins is different and seems to have little relation with the binding constant. The activity of lysozyme/trypsin/pepsin decreases with the addition of AuNPs.

Protein corona-guided tumor targeting therapy via the surface modulation of low molecular weight PEG

The discovery of protein corona (PC) formed on the surface of nanomaterials has promoted research on PC regulation to guide the biological behavior of nanomaterials in vivo. Different from changing the size, shape, and surface charge of nanoparticles, we propose to control the nature of PC by adjusting the molecular weight of low molecular weight polyethylene glycol (LMW PEG, not more than 1000 Da) on the surface of the particles. After excluding the influence of physicochemical factors of PEGylated gold nanoparticles (GNPs), different proteins on the surface of PEGylated GNPs were separated and identified after incubation with human plasma. It is noted that GNP-550 bearing PEG chains of 550 Da absorbed more transferrin responsible for tumor targeting than the other two particles, i.e., GNP-350 and GNP-1000. To validate our speculation, doxorubicin (Dox) was inserted between GNPs and PEGs to explore the cellular and animal studies of Dox-conjugated GNPs. Interestingly, Dox-containing Conj-550 also showed the highest intracellular uptake, cytotoxicity, and apoptosis against HepG2 cells, as well as the best tumor targeting effect and antitumor efficacy in Heps-bearing mice. This protein corona-guided tumor targeting therapy by transferrin provides a new perspective on the function modulation of nanomedicine via LMW PEGs.

Redox-sensitive polymeric micelles with aggregation-induced emission for bioimaging and delivery of anticancer drugs

BACKGROUND

Nano-drug delivery systems show considerable promise for effective cancer therapy. Polymeric micelles have attracted extensive attention as practical nanocarriers for target drug delivery and controlled drug delivery system, however, the distribution of micelles and the release of the drug are difficult to trace in cancer cells. Therefore, the construction of a redox-sensitive multifunctional drug delivery system for intelligent release of anticancer drugs and simultaneous diagnostic imaging and therapy remains an attractive research subject.

RESULTS

To construct a smart drug delivery system for simultaneous imaging and cancer chemotherapy, mPEG-ss-Tripp was prepared and self-assembled into redox-sensitive polymeric micelles with a diameter of 105 nm that were easily detected within cells using confocal laser scanning microscopy based on aggregation-induced emission. Doxorubicin-loaded micelles rapidly released the drug intracellularly when GSH reduced the disulfide bond. The drug-loaded micelles inhibited tumor xenografts in mice, while this efficacy was lower without the GSH-responsive disulfide bridge. These results establish an innovative multi-functional polymeric micelle for intracellular imaging and redox-triggered drug deliver to cancer cells.

CONCLUSIONS

A novel redox-sensitive drug delivery system with AIE property was constructed for simultaneous cellular imaging and intelligent drug delivery and release. This smart drug delivery system opens up new possibilities for multifunctional drug delivery systems.

Biological Behavior Regulation of Gold Nanoparticles via the Protein Corona

One of the difficulties in the translation of gold nanoparticles (GNPs) into clinical practice is the formation of the protein corona (PC) that causes the discrepancy between the in vitro and in vivo performance of GNPs. The PC formed on the surface of GNPs gives them a biological identity instead of an initial synthetic one. In most instances, this biological identity increases the particle size, leads to more clearance by the reticuloendothelial system, and causes less uptake by target cells. However, the performance of GNPs can still be improved by rewriting their original surface chemistry via the PC. This review specifically focuses on discussing the main influence factors, including the biological environment and physicochemical properties of GNPs, which affect the production and status of the PC. The status of the PC such as the amount, thickness, and composition subsequently influence the biological behavior of GNPs, especially their cellular uptake, cytotoxicity, biodistribution, and tumor targeting. Further understanding and revealing the impacts of the PC on the biological behavior of GNPs can be a promising and important strategy to regulate and improve the performance of GNP-based biosystems in the future.

Performance of Doxorubicin-Conjugated Gold Nanoparticles: Regulation of Drug Location

Drug-conjugated gold nanoparticles (GNPs), which are generally constructed with many molecules of thiol-terminated polyethylene glycol (PEG)-drug decorated on their surfaces via a thiol-Au covalent bond, are promising and efficient nanoprodrugs. However, because of the exposure of the hydrophobic drug molecules on the surface of the conjugate, in vivo stability, opsonization, and subsequent inefficient therapy become the main issues of this system. To solve these problems without complicating the structures of gold conjugates, herein we propose a method to change the relative position of PEG and the drug. A novel gold conjugate (GNP-NHN═Dox-mPEG) with doxorubicin (Dox) shielded by PEGylation on the surface of GNPs is designed. It demonstrates improved solubility, stability, and dispersion and achieves a two-step stimulus-responsive drug release in response to an acidic environment in lysosomes and then esterase in the cytoplasm. This unique manner of release enables the cytoplasm to act as a reservoir for sustained drug delivery into the nucleus to improve antitumor efficacy in vivo. The intratumoral drug concentrations of the conjugate reach 14.4 ± 1.4 μg/g at 8 h, a two-fold increase in the drug concentration compared with that of the doxorubicin hydrochloride group. This molecular design and regulation approach is facile but important in modulating the in vivo performance of nanovehicles and demonstrates its vital potential in developing effective nanoparticle-based drug delivery agents.