Minghao Sun

Functionalization of quantum dots with multidentate zwitterionic ligands: impact on cellular interactions and cytotoxicity

Surface functionalization of nanoparticles is an important determinant of their interactions with biological compartments at the nano-bio interface. In this paper, a series of multidentate zwitterionic polymeric ligands were synthesized and used to functionalize the surface of quantum dots (QDs). The structure of polymer ligands was designed by changing the molar ratio of reactants and precursors used in the reaction. A three-component micro-emulsion method was developed to improve the efficiency of ligand exchange and avoid cross-linking reactions. Highly stable, compact and biocompatible zwitterionic QDs with different surface charge densities were obtained after ligand exchange. Variation of the surface charge density of QDs was verified by zeta potential measurements. The interaction of zwitterionic QDs with different cancer and normal cell lines (KB 3-1, COLO 205 and HEK 293) was surface charge density dependent. From cell viability studies, it was shown that higher surface charge density resulted in lower cytotoxicity of zwitterionic QDs when incubated with both cancer and normal cell lines. Furthermore, the feasibility of conjugating functionalized QDs (coated with amine zwitterionic polymer ligands) with a biomolecule was demonstrated. This was exemplified by the conjugation of amine zwitterionic QDs with a cRGD peptide, which showed improved interaction of cRGD-QDs with ανβ3 integrin receptors expressed on U87MG glioblastoma tumor cells. Engineering the surface charge density and functionalization of nanoparticles, by multidentate zwitterionic ligands, provides a strategy to tune the surface properties of QDs, which impacts their cytotoxicity and cellular interaction at the nano-bio interface.

Highly stable intrinsically radiolabeled indium-111 quantum dots with multidentate zwitterionic surface coating: dual modality tool for biological imaging

Here we describe a novel strategy to incorporate indium-111 into near infrared (NIR) emitting Cu-In-Se quantum dots (CIS-QDs) to synthesize intrinsically radiolabeled QDs (rQDs), as a quantitative tool for in vivo SPECT/fluorescence imaging. Multidentate zwitterionic polymer ligands were used to functionalize and improve the stability of CIS-rQDs and reduce nonspecific binding with plasma proteins/cell membrane. CIS-rQDs were taken up by colorectal adenocarcinoma (COLO-205) and human epidermoid carcinoma (KB-3-1) cells at low uptake rate (∼0.4%, 2 × 105 QDs per cell at 24 h) and reduced nonspecific interaction of zwitterionic CIS-rQDs with cells was observed by fluorescence microscopy. The cytotoxicity of CIS-rQDs was reduced due to the low toxic inorganic composition of QDs and multidentate zwitterionic surface coating. In 5 out of 6 nude mice bearing either COLO-205 or KB-3-1 tumor, both SPECT and fluorescence imaging demonstrated passive localization of CIS-rQDs in the tumor as early as 6 h post-injection. In these mice the passive accumulation of CIS-rQDs in the tumor, due to leaky vasculature, ranged from ∼0.3% ID per g to ∼4.6% ID per g at 48 h post-injection (from region of interest analysis of SPECT imaging). This intrinsic radio-labeling strategy provides a nanoparticle platform which incorporates imaging and potentially therapeutic radionuclides with retention of fluorescence intensity. It also provides complimentary quantitative data capabilities for both in vivo SPECT imaging and radiotracer ex vivo analysis.

Biodistribution and PET imaging of 89-zirconium labeled cerium oxide nanoparticles synthesized with several surface coatings

Cerium oxide nanoparticles (CONPs) have unique surface chemistry allowing catalyst-like antioxidant properties, and are being investigated for several disease indications in medicine. Studies have utilized surface modified CONPs toward this application, but have been lacking in comprehensive biodistribution and pharmacokinetic data and a direct comparison to uncoated CONPs. We developed an enhanced single-pot synthesis of several coated CONPs and an efficient intrinsic core labeling of CONPs with the clinical PET isotope, zirconium-89, allowing detailed PET imaging and ex vivo biodistribution. All coated [89Zr]-CONPs showed benefit in terms of biodistribution compared to uncoated [89Zr]-CONPs, while retaining the intrinsic antioxidant properties. Among these, poly(acrylic acid) coated CONPs demonstrated excellent candidacy for clinical implementation due to their enhanced renal clearance and low reticuloendothelial system uptake. This work also demonstrates the value of intrinsic core labeling and PET imaging for evaluation of nanoparticle constructs to better inform future studies towards clinical use.

Abstract 4142: Surface engineering of quantum dots with multidentate polymer ligands: surface charge density affect on interactions at the nano-bio interface in vitro.

Nanomedicine is an emerging field with increasing applications in cancer diagnosis and therapy. However, these applications strongly depend on the nature of cellular and tissue interactions in vitro and in vivo, which in turn is strongly influenced by properties of nanomaterials. The effect of surface modification of nanoparticles on their interaction with biological compartments is not yet well understood. Here, a series of multidentate zwitterionic polymeric ligands were synthesized and applied to functionalize the surface of quantum dots (QDs), which have been extensively used for fluorescent imaging in vitro and in vivo. The structure of polymeric ligands was tuned by changing their composition, and QDs with different surface charge density were obtained using these polymers as coating ligands. Highly stable, compact and biocompatible hydrophilic QDs were obtained after ligand exchange and QDs were tuned to have zeta potentials from -25 mV to -55 mV. Compared with small zwitterionic ligand coated QDs, cell viability of multidentate zwitterionic polymer ligand coated QDs were improved due to their better bio-stability originating from the multiple chelation of polymer ligand with surface of nanoparticles. The interaction of QDs, having different surface charge density, with various tumor/normal cell lines (KB 3-1, KB 8-5, COLO 205, A-549, FaDu, SK-OV-3, and HEK-293) was investigated. The surface charge densities of the nanoparticles profoundly influence their interactions with most cells. High surface charge (-55 mV and -40 mV) density increased interaction of nanoparticles with some cell membranes of tumor cells such as COLO 205 and KB 3-1. However, other tumor cells showed less sensitivity to the surface charge density of nanoparticles and displayed reduced nonspecific binding (FaDu, A-549, and SK-OV-3). The normal prostate cell line HEK-293 showed lowest interaction with these zwitterionic QDs. The surface bioconjugation of QDs with folic acid increased the intracellular internalization of QDs in KB 3-1 cell lines (with high folate receptor expression) compared with COLO 205 cell lines (low folate receptor expression), most likely due to the folate receptor mediated endocytosis. From our initial investigations, the surface properties of nanoparticles influence the nature of their interactions at the cellular level. Such information could guide in vivo studies of these nanomaterials within an intact in vivo environment. Citation Format: Minghao Sun, Purnima Jose, Likun Yang, Gobalakrishnan Sundaresan, Li Wang, Jamal Zweit. Surface engineering of quantum dots with multidentate polymer ligands: surface charge density affect on interactions at the nano-bio interface in vitro . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4142. doi:10.1158/1538-7445.AM2013-4142