Protein-Adsorbed Magnetic-Nanoparticle-Mediated Assay for Rapid Detection of Bacterial Antibiotic Resistance.

Antibiotic susceptibility tests have been used for years as a crucial diagnostic tool against antibiotic-resistant bacteria. However, due to a lack of biomarkers specific to resistant types, these approaches are often time-consuming, inaccurate, and inflexible in drug selections. Here, we present a novel susceptibility test method named protein-adsorbed nanoparticle-mediated matrix-assisted laser desorption-ionization mass spectrometry, or PANMS. Briefly, we adsorb five different proteins (ß-casein, α-lactalbumin, human serum albumin, fibrinogen, and avidin) onto the surface of Fe3O4. Upon interaction with bacteria surface, proteins were displaced from the nanoparticle surface, the amounts of which were quantified by matrix-assisted laser desorption ionization mass spectrometry. We find that the protein displacement profile was different distinctive among different bacteria strains and, in particular, between wild-type and drug-resistant strains. More excitingly, we observe bacteria resistant to drugs of the same mechanisms share similar displacement profiles on a linear discriminant analysis (LDA) map. This suggests the possibility of using PANMS to identify the type of mechanism behind antibiotic resistance, which was confirmed in a blind test. Given that PANMS is free of drug incubation and the whole procedure takes less than 50 min, it holds great potential as a high-throughput, low-cost, and accurate drug susceptibility test in the clinic.

Red Blood Cell-Facilitated Photodynamic Therapy for Cancer Treatment.

Photodynamic therapy (PDT) is a promising treatment modality for cancer management. So far, most PDT studies have focused on delivery of photosensitizers to tumors. O2, another essential component of PDT, is not artificially delivered but taken from the biological milieu. However, cancer cells demand a large amount of O2 to sustain their growth and that often leads to low O2 levels in tumors. The PDT process may further potentiate the oxygen deficiency, and in turn, adversely affect the PDT efficiency. In the present study, a new technology called red blood cell (RBC)-facilitated PDT, or RBC-PDT, is introduced that can potentially solve the issue. As the name tells, RBC-PDT harnesses erythrocytes, an O2 transporter, as a carrier for photosensitizers. Because photosensitizers are adjacent to a carry-on O2 source, RBC-PDT can efficiently produce 1O2 even under low oxygen conditions. The treatment also benefits from the long circulation of RBCs, which ensures a high intraluminal concentration of photosensitizers during PDT and hence maximizes damage to tumor blood vessels. When tested in U87MG subcutaneous tumor models, RBC-PDT shows impressive tumor suppression (76.7%) that is attributable to the codelivery of O2 and photosensitizers. Overall, RBC-PDT is expected to find wide applications in modern oncology.

Fe5C2 nanoparticles with high MRI contrast enhancement for tumor imaging.

An ancient material for magnetic resonance (MR) imaging: For the first time, Fe5C2 is prepared as colloidal stable nanoparticles with good aqueous stability. The nanoparticles boast strong magnetization, excellent chemical inertness, low toxicity, and one of the highest r2 relaxivities reported to date. These nanoparticles hold great potential in MR imaging as well as in other biomedical areas.

Casein-Coated Fe5C2 Nanoparticles with Superior r2 Relaxivity for Liver-Specific Magnetic Resonance Imaging.

Iron oxide nanoparticles have been extensively used as T2 contrast agents for liver-specific magnetic resonance imaging (MRI). The applications, however, have been limited by their mediocre magnetism and r2 relaxivity. Recent studies show that Fe5C2 nanoparticles can be prepared by high temperature thermal decomposition. The resulting nanoparticles possess strong and air stable magnetism, suggesting their potential as a novel type of T2 contrast agent. To this end, we improve the synthetic and surface modification methods of Fe5C2 nanoparticles, and investigated the impact of size and coating on their performances for liver MRI. Specifically, we prepared 5, 14, and 22 nm Fe5C2 nanoparticles and engineered their surface by: 1) ligand addition with phospholipids, 2) ligand exchange with zwitterion-dopamine-sulfonate (ZDS), and 3) protein adsorption with casein. It was found that the size and surface coating have varied levels of impact on the particles' hydrodynamic size, viability, uptake by macrophages, and r2 relaxivity. Interestingly, while phospholipid- and ZDS-coated Fe5C2 nanoparticles showed comparable r2, the casein coating led to an r2 enhancement by more than 2 fold. In particular, casein coated 22 nm Fe5C2 nanoparticle show a striking r2 of 973 mM(-1)s(-1), which is one of the highest among all of the T2 contrast agents reported to date. Small animal studies confirmed the advantage of Fe5C2 nanoparticles over iron oxide nanoparticles in inducing hypointensities on T2-weighted MR images, and the particles caused little toxicity to the host. The improvements are important for transforming Fe5C2 nanoparticles into a new class of MRI contrast agents. The observations also shed light on protein-based surface modification as a means to modulate contrast ability of magnetic nanoparticles.

Gd-encapsulated carbonaceous dots with efficient renal clearance for magnetic resonance imaging.

Nanoprobes for MRI and optical imaging are demonstrated. Gd@C-dots possess strong fluorescence and can effectively enhance signals on T1 -weighted MR images. The nanoprobes have low toxicity, and, despite a relatively large size, can be efficiently excreted by renal clearance from the host after systemic injection.

Polyaspartic acid coated iron oxide nanoprobes for PET/MRI imaging.

Iron oxide nanoparticles, due to their exceptional magnetic property, biocompatibility, and biodegradability, have long been studied as contrast agents for magnetic resonance imaging (Xie et al., Curr Med Chem 16(10):1278-1294, 2009; Xie et al., Adv Drug deliv Rev 62(11):1064-1079, 2010). While previous applications mostly target reticuloendothelial system (RES) organs such as liver and lymph nodes, recent efforts have been made to impart targeting peptides or antibodies onto particle surface to enable site-specific targeting after systemic administration (Xie et al., Adv Drug Deliv Rev 62(11):1064-1079, 2010; Cai and Chen, Small 3(11):1840-1854, 2007; Corot et al., Adv Drug Deliv Rev 58 (14):1471-1504, 2006; Xie et al., Acc Chem Res 44(10):883-892). Moreover, other imaging functionalities can be loaded onto nanoparticles to achieve multimodality imaging probes (Cai and Chen, Small 3(11):1840-1854, 2007; Lee et al., J Nucl Med Soc Nucl Med 49(8):1371-1379, 2008). In this protocol, we describe the procedure of constructing an iron oxide nanoparticle (IONP)-based probe with high affinity towards integrin αvß3 for positron emission tomography (PET) and magnetic resonance imaging (MRI) dual modality imaging. The related characterizations and validation experiments, including particle concentration determination, Prussian blue staining, animal model preparation, and in vivo PET/MRI imaging will also be discussed.

RGD-modified apoferritin nanoparticles for efficient drug delivery to tumors.

Ferritin (FRT) is a major iron storage protein found in humans and most living organisms. Each ferritin is composed of 24 subunits, which self-assemble to form a cage-like nanostructure. FRT nanocages can be genetically modified to present a peptide sequence on the surface. Recently, we demonstrated that Cys-Asp-Cys-Arg-Gly-Asp-Cys-Phe-Cys (RGD4C)-modified ferritin can efficiently home to tumors through RGD-integrin αvß3 interaction. Though promising, studies on evaluating surface modified ferritin nanocages as drug delivery vehicles have seldom been reported. Herein, we showed that after being precomplexed with Cu(II), doxorubicin can be loaded onto RGD modified apoferritin nanocages with high efficiency (up to 73.49 wt %). When studied on U87MG subcutaneous tumor models, these doxorubicin-loaded ferritin nanocages showed a longer circulation half-life, higher tumor uptake, better tumor growth inhibition, and less cardiotoxicity than free doxorubicin. Such a technology might be extended to load a broad range of therapeutics and holds great potential in clinical translation.