Human Immune Protein C1q Selectively Disaggregates Carbon Nanotubes

Surface engineering of colloidal nanoparticles

Synthesis of engineered colloidal nanoparticles (NPs) with delicate surface characteristics leads to well-defined physicochemical properties and contributes to multifunctional applications. Surface engineering of colloidal NPs can improve their stability in diverse solvents by inhibiting the interparticle attractive forces, thus providing a prerequisite for further particle manipulation, fabrication of the following materials and biological applications. During the last decades, surface engineering methods for colloidal NPs have been well-developed by numerous researchers. However, accurate control of surface properties is still an important topic. The emerging DNA/protein nanotechnology offers additional possibility of surface modification of NPs and programmable particle self-assembly. Here, we first briefly review the recent progress in surface engineering of colloidal NPs, focusing on the improved stability by grafting suitable small molecules, polymers or biological macromolecules. We then present the practical strategies for nucleic acid surface encoding of NPs and subsequent programmable assembly. Various exciting applications of these unique materials are summarized with a specific focus on the cellular uptake, bio-toxicity, imaging and diagnosis of colloidal NPs in vivo. With the growing interest in colloidal NPs in nano-biological research, we expect that this review can play an instructive role in engineering the surface properties for desired applications.

Effects of the surface polarity of nanomaterials on their interaction with complement protein gC1q

There are increasing studies about the biocompatibility of nanomaterials (NMs) as their applications in biomedicine become more widespread. The biocompatibility of NMs involves the recognition by the immune system including complement protein gC1q. In this work, the interaction of graphene oxide (GO) and self-assembled monolayer (SAM)-coated gold (111) surface with gC1q was studied by molecular dynamics (MD) simulations. The impacts of surface polarity of GO on its interaction with gC1q and the possible immune response were discussed by comparing the binding behavior of gC1q to the GO sheets with different oxidation degrees (i.e., C5O1(OH)1 and C20O1(OH)1). We find the ghB module of gC1q tends to bind to GO sheet (C5O1(OH)1) with strong surface polarity, as the ghB module forms more hydrogen bonds with this GO sheet. On the other hand, the ghC module of gC1q tends to bind to GO (C20O1(OH)1) with weak surface polarity, as the ghC module tends to form pi-pi stacking and stronger hydrophobic interaction with this GO sheet. Similar phenomena are also found in the adsorption of gC1q with SAM: ghC prefers to bind to hydrophobic CH3-SAM, and ghB prefers to bind to charged COO-SAM. The different binding modules of gC1q may result in different activation levels of complement system. Our findings suggest that the surface polarity of NMs regulates the interaction of NMs with gC1q and the subsequent immune response. In other words, the biocompatibility of NMs may be regulated by adjusting their surface polarity.

Precision Nanomedicine Development Based on Specific Opsonization of Human Cancer Patient-Personalized Protein Coronas

When a nanomedicine is administrated into the human body, biomolecules in biological fluids, particularly proteins, form a layer on the surface of the nanoparticle known as a "personalized protein corona". An understanding of the formation and behavior of the personalized protein corona not only benefits the nanotherapy treatment efficacy but also can aid in disease diagnosis. Here we used Gd@C₈₂(OH)₂₂ nanoparticles, a nanomedicine effective against several types of cancer, as a model nanomedicine to investigate the natural protein fingerprint of the personalized protein corona formed in 10 human lung squamous cell carcinoma patients. Our analysis revealed a specific biomarker, complement component C1q, in lung cancer personalized protein coronas, abundantly bound to Gd@C₈₂(OH)₂₂ NPs. This binding altered the secondary structure of C1q protein and led to the activation of an innate immune response, which could be exploited for cancer immune therapy. On the basis of this finding, we provide a new strategy for the development of precision nanomedicine derived from opsonization of a unique protein fingerprint within patients. This approach overcomes the common pitfall of protein corona formation and exploits the corona proteins to generate a precision nanomedicine and diagnostic tool.

Hide and Seek: Nanomaterial Interactions With the Immune System

Engineered nanomaterials hold promise for a wide range of applications in medicine. However, safe use of nanomaterials requires that interactions with biological systems, not least with the immune system, are understood. Do nanomaterials elicit novel or unexpected effects, or is it possible to predict immune responses to nanomaterials based on how the immune system handles pathogens? How does the bio-corona of adsorbed biomolecules influence subsequent immune interactions of nanomaterials? How does the grafting of polymers such as poly(ethylene glycol) onto nanomaterial surfaces impact on these interactions? Can ancient immune evasion or “stealth” strategies of pathogens inform the design of nanomaterials for biomedical applications? Can nanoparticles co-opt immune cells to target diseased tissues? The answers to these questions may prove useful for the development of nanomedicines.

Recognition protein C1q of innate immunity agglutinates nanodiamonds without activating complement

Nanodiamonds are promising nanomedicines for diagnostic and therapeutic applications. As nanodiamonds are mainly administered intravenously, it is critical to understand the humoral immune response upon exposure to nanodiamonds. Here, we report the interactions of pristine, oxidized, and PEG-functionalized nanodiamonds with human complement, an important part of our humoral innate immunity. In particular, we report the nanodiamond binding properties of the recognition protein of the classical complement pathway: C1q, which also takes part in many other physiological and pathological processes. Our results show similar trends in the effects of C1q on the three types of nanodiamonds. Complement activation assays using human serum show that the nanodiamonds trigger slight activities via the alternative pathway and no response via the classical pathway. Nevertheless, surface plasmon resonance shows that C1q binds the nanodiamonds and transmission electron microscopy reveals their agglutination. Studies with macrophages further show that C1q attachment affects their phagocytosis and cytokine response.

Mode of PEG Coverage on Carbon Nanotubes Affects Binding of Innate Immune Protein C1q

Surface modification of nanoparticles with poly(ethylene glycol) (PEG) is used in biomedicine to increase the circulation time of the particles after intravenous injection. Here, we study the interaction of PEG-covered carbon nanotubes (CNTs) with the serum complement protein C1q. Besides being the target-recognizing unit of the initiating complex for the classical pathway of complement in our innate immune system, C1q is involved in a range of important physiological processes. We modified the surface of multiwalled CNTs with covalently grafted PEG and physically adsorbed PEG. Transmission electron microscopy revealed the interaction of these PEG-coated CNTs with C1q. We found abundant C1q coverage on the PEG-grafted CNTs but not on the CNTs with adsorbed PEG. We tested the ability of these CNTs to activate the complement system using in vitro complement activation assays. None of the CNTs studied activated the C1q-dependent classical complement pathway. These findings are pertinent to the safe design and novel biomedical applications of PEGylated CNTs.