ACS Appl Mater Interfaces. 2019 May 8;11(18):16421-16429. doi: 10.1021/acsami.9b05599.

Albumin modified cationic nanocarriers to potentially create a new platform for drug delivery systems

Zhicheng Pan1, 3, Xueling He1, 2, Nijia Song1, Danxuan Fang1, Zhen Li1*, Jiehua Li1, Feng Luo1, Jianshu Li1, Hong Tan1* and Qiang Fu1

 

1College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, China

2Laboratory Animal Center of Sichuan University, Chengdu 610041, China

3Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L8

 

Abstract

Cationic nanocarriers have emerged as promising nanoparticles systems for the effective delivery of anticancer drugs or nucleic acid to tumor cells. Positive charge is desirable for promoting cell internalization, while it also causes some adverse effects, such as toxicity and rapid clearance by mononuclear phagocytic systems. Herein, a new strategy that utilizing albumin to modify cationic polymer micelles, which forming protein corona to improve the surface physiochemical properties is reported. The corona with monolayer or multilayer was constructed depending on the albumin concentration, and the proteins would denature in different degrees due to the interaction with the surface of cationic micelles. It is demonstrated that multilayer albumin corona is beneficial to prevent macrophages uptake, increase accumulation in tumor site and reduce toxic side effects to normal tissue. Our work provides a promising method to modify cationic nanopaltform with optimizing the biosecurity and bioavailability for potential application in drug delivery.

PMID: 30995005

 

Supplement

The rapid development of nanomaterials offered a great application potential to improve the treatment and diagnosis of disease. Many smarter nanocarriers were fabricated through sophisticated molecule structure design and integration of multifunctional groups. Diversification of functions and nanoscale structure confer nanocarriers a very large surface-to-volume ratio and undesirable surface properties, such as hydrophobicity and high charge density, leading to some adverse effects in vivo. The nanocarriers will be coated by hundreds of plasma proteins immediately after entering a physiological environment, forming what is known as “protein corona”, which endues nanocarriers a new biological identity in contrast to their initial synthetic identity.1 Among the protein corona, immunoglobulins (IgG) and complement proteins,2 called opsonin proteins, are known to associate with mononuclear phagocytic systems (MPS), which will promote recognized and subsequent elimination of nanocarriers.3 Therefore, to prevent the undesirable protein adsorption of nanocarries plays a key role in improving the biocompability and therapy effect.4

Unexpectedly, some proteins display ideal raw materials for drug delivery, since they have the natural advantages over synthetic polymers, such as the metabolism, biodegradability and low toxicity.5 For instance, albumin as the most abundant plasma protein, has been widely used as a versatile protein carriers for drug delivery system, due to its excellent biocompatibility, lack of toxicity and immunogenicity, inexpensive production, as well as easy storage and biostability.6 Abraxane® via the hydrophobic interaction between human serum albumin and paclitaxel (PTX) to form albumin-drug nanocarriers has been approved by US Food and Drug Administration (FDA) and become a first-line anti-cancer drug for breast, lung and pancreatic cancer.7

Therefore, we combine these two seemingly contradictory things, providing a new method that using albumin to modify nanocarriers to effectively improve the biodistribution and biosecurity for cationic nano-platform using in the drug delivery system (Figure 1). In our previously study, we found that gemini quaternary ammonium (GQA) can strengthen the permeability of polyurethane micelles for enhanced cellular uptake and efficient drug delivery.8 However, we also have found that the exposed cationic GQA might puncture the cell membrane, damage the integrity of cell and potentially cause apoptosis. In order to eliminate the adverse protein absorption and improve biosecurity, albumin was primarily utilized to modify the cationic polyurethane micelles to obtain a micelles-albumin complex (MAC).

Depending on the concentration of the albumin, the adsorbed proteins form corona with monolayer or multilayers surrounding the micelles (Figure 2). The naked G8mE1900 micelles distribute individually with regular and spherical shape, and the diameters is in the range of 70~90 nm. BSA protein also display regular sphere with smaller size range of 30-50 nm (Figure 2B). Meanwhile, the morphology has a great change when the albumin concentration reach to 0.1 mg/ml. As shown in Figure 2C, a protein coating layer surrounding micellar surface can be obviously observed. The size of G8mE1900-LB (naked G8mE1900 micelles modified by low albumin concentration) has a slight increased with irregular spherical shape. Compared to the naked micelles, the size of G8mE1900-LB has exceed ~50 nm, which is exactly the diameter of a single BSA. Therefore, it can be inferred that the MACs were coated with a monolayer protein corona under 0.1 mg/ml BSA. As the concentration of BSA reaches to 2 mg/ml, the size of G8mE1900-HB (naked G8mE1900 micelles modified by high albumin concentration) expanded to 150~200 nm, owing to more proteins are adsorbed on the micellar surface to construct multilayer protein corona.

The albumin corona served as a protective coating for cationic micelles, which could inhibit the opsonin proteins adsorption during blood circulation and relieve the elimination by reticuloendothelial system (RES), improving biodistribution and biosafety in vivo (Figure 3). The albumin modification could noticeably enhance the bioavailability and biodistribution of cationic nanocarriers, reduce the accumulation of drug in normal organs, and improve the drug concentration in the tumor site (Figure 3A and 3B). As shown in Figure 3C and 3E, the growth of tumors was dramatically suppressed by the treatment of various PTX formulations. The cationic micelles with or without modified by albumin have a similar effect on tumor treatment. The body weights (Figure 3D) and survival rate (Figure 3F) of mice demonstrate that the MACs could markedly reduce toxic side effect of therapeutic agents to normal tissues and organs. Histological evaluation was also conducted to examine the apoptosis level and organizational damage in the tumors and the other normal tissues after treatments (Figure 3G and 3H). Taxol® and naked G8mE1900 micelles containing gemini cationic group are easily captured by immune cells and trapped in liver, thereby causing certain liver toxicity. Exhilaratingly, the MACs exhibited no liver damage. These results strongly confirmed that the albumin corona could significantly improve biosafety without changing the tumor therapy efficacy compared with naked cationic nanocarriers.

Multilayer Albumin created a steric barrier to inhibit the opsonin proteins adsorption, hence it could prevent macrophages uptake, avoided the retention in normal tissues and enhance the drug accumulation in tumor site. MACs could significantly improve biosafety without changing the tumor therapy efficacy compared with naked cationic nanocarriers. Our work provide a promising method to modify cationic nanopaltform with optimizing the biosecurity and bioavailability for potential application in vivo.

 

 

Figure 1. A new strategy to modify cationic nanocarriers is described, in which using albumin protein corona to optimize the biosecurity and bioavailability of cationic nanocarriers. The multilayer corona is created a steric barrier to prevent macrophages uptake, increase accumulation in tumor site and reduce the retention and toxic side effects to normal tissue.

 

 

Figure 2. TEM images of A) G8mE1900 (1 mg/ml), B) BSA protein (1 mg/ml), C) G8mE1900 with low BSA concentration (0.1 mg/ml) and D) G8mE1900 with high BSA concentration (2 mg/ml).

 

 

Figure 3. In vivo biodistribution and therapeutic efficacy of naked micelles and MACs in mice bearing HeLa tumor model. (A) In vivo fluorescence images of tumor-bearing nude mice receiving intravenous injection of fluorescent-labeled naked micelles and MACs after 60 min. (B) Quantification of the fluorescent in Liver, Kidney and Tumor after 60 min injection. Changes of tumor volume (C) and body weight (D), mean weights of tumors (E) and survive rates (F) of tumors separated from animals at 21 days post-injection. H&E staining of liver (G) and tumors (H) sections separated from animals receiving different treatments. (*) represents statistical significance P < 0.001: the drug loaded micelles versus all the control samples. (**) P < 0.01: the drug loaded micelles versus PBS.

 

 

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