Tempo-spatially resolved cellular dynamics of human immunodeficiency virus transacting activator of transcription (Tat) peptide-modified nanocargos in living cells

Ultrasensitive detection of tyrosinase with click reaction-combined dark-field imaging platform

Tyrosinase (TYR) is an essential oxidase that is responsible for the regulation of multiple physiological processes and diseases. Achieving the trace and reliable detection of TYR in complex biological samples is of great significance for the diagnosis of TYR-related diseases, but which faces a great challenge. In this study, we developed an ingenious and powerful method for the ultrasensitive detection of TYR by click reaction-combined dark-field microscopy. This method begins with the formation of cuprous ions (Cu+) based on the reduction of copper ions (Cu2+) by ascorbic acid (AA). Subsequently, the formed Cu+ can catalyze the crosslinking between azide- and alkyne-functionalized gold nanoparticles, causing a significant red-shift in the scattering spectrum. However, AA can chelate with TYR, which inhibits the generation of Cu+ and subsequent click reaction, thus achieving TYR-controlled scattering spectral shift. The proposed sensing platform shows a good linear detection range of 0.01-0.8 U/L with a low detection limit of 0.003 U/L, which is three orders of magnitude lower than the best performance of TYR sensing probes reported to date. Most importantly, the strategy has the ability to reliably and accurately detect TYR in serum sample, suggesting its potential clinical application in diagnosing TYR-related diseases. This visual sensing platform offers promising prospects for future research in enzymatic analysis and biomedical diagnostics.

Ligand-Receptor Interaction Triggers Hopping and Sliding Motions on Living Cell Membranes

Exploring the surface-capturing and releasing processes of nanocargo on the living cell membrane is critical for understanding the membrane translocation process. In this work, we achieve total internal reflection scattering (TIRS) illumination on a commercial dark-field optical microscope without the introduction of any additional optical components. By gradually reducing the diaphragm size in the excitation light path, the angle of the incident beam can be well manipulated. Under optimal conditions, the excitation light can be totally reflected at the glass/water interface, resulting in a thin layer of evanescent field for TIRS illumination. Due to the exponential decay feature of the evanescent field, the displacement of the nanocargo along the vertical direction can be directly resolved in the intensity track. With this method, we selectively monitor the dynamics of the transferrin-modified nanocargo on the living cell membrane. Transition between confined diffusion and long-range searching is involved in the binding site recognition process, which exhibits non-Gaussian and nonergodic-like behavior. More interestingly, 2D fast sliding and 3D hopping motions are also distinguished on the fluidic cell membrane, which is essentially modulated by the strength of ligand-receptor interactions, as revealed by the free-energy profiles. These heterogeneous and dynamic interactions together control the diffusion mode of the nanocargo on the lipid membrane and, thus, determine the cellular translocation efficiency.

Brightness Analysis per Moving Particle: In Situ Analysis of Alkaline Phosphatase in Living Cells

In situ quantitative analysis of enzymes such as phosphatase is important to understand a number of involved biological processes ranging from various metabolisms to signal transduction and cellular regulation. In this paper, a novel in situ measurement strategy was proposed to detect alkaline phosphatase (ALP) activity in different locations within single living cells. The principle is based on the measurement of the resonance light scattering brightness ratio (SBR) per moving nanoparticle that forms in an ALP-related chemical reaction. In the method, a novel resonance light scattering correlation spectroscopy (RLSCS) system was developed using two lasers for illumination or two detection channels. Using the gold nanoparticles (AuNPs) as probes, the Au@Ag nanoparticles (Au@Ag NPs) formed due to the ALP-catalyzed hydrolysis of ascorbic acid 2-phosphate (AAP) and the subsequent reduction-deposition reaction of Ag ions that occurred on the AuNPs. The SBR value per moving particle was determined based on the obtained RLS intensity traces and RLSCS curves. The SBR value was found to be not influenced by the intracellular viscosity and size that was confirmed in the experiments. The linear relation between the SBR and ALP activity was established and applied to detect ALP activity and evaluate the inhibition of different drugs. Finally, the method was successfully used to in situ measure ALP activity within living cells. The method overcomes the shortcoming of conventional methods that lack quantitative analysis and are susceptible to intracellular viscosity.

The Peptide Functionalized Inorganic Nanoparticles for Cancer-Related Bioanalytical and Biomedical Applications

In order to improve their bioapplications, inorganic nanoparticles (NPs) are usually functionalized with specific biomolecules. Peptides with short amino acid sequences have attracted great attention in the NP functionalization since they are easy to be synthesized on a large scale by the automatic synthesizer and can integrate various functionalities including specific biorecognition and therapeutic function into one sequence. Conjugation of peptides with NPs can generate novel theranostic/drug delivery nanosystems with active tumor targeting ability and efficient nanosensing platforms for sensitive detection of various analytes, such as heavy metallic ions and biomarkers. Massive studies demonstrate that applications of the peptide-NP bioconjugates can help to achieve the precise diagnosis and therapy of diseases. In particular, the peptide-NP bioconjugates show tremendous potential for development of effective anti-tumor nanomedicines. This review provides an overview of the effects of properties of peptide functionalized NPs on precise diagnostics and therapy of cancers through summarizing the recent publications on the applications of peptide-NP bioconjugates for biomarkers (antigens and enzymes) and carcinogens (e.g., heavy metallic ions) detection, drug delivery, and imaging-guided therapy. The current challenges and future prospects of the subject are also discussed.

Biomedical applications of the peptide decorated gold nanoparticles

Currently, peptide-nanoparticle (NP) conjugates have been demonstrated to be efficient and powerful tools for the treatment and the diagnosis of various diseases as well as in the bioimaging application. Several bioconjugation strategies have been adopted to formulate the peptide-NP conjugates. In this review, we discuss the exciting applications of peptide-gold (Au) NP conjugates in the area of drug delivery, targeting, cancer therapy, brain diseases, vaccines, immune modulation, biosensor, colorimetric detection of heavy metals, and bio-labeling in vitro and in vivo models. Within this framework, various approaches such as radiotherapy, photothermal therapy, photodynamic therapy and chemo-photothermal therapy have been demonstrated for the treatment of several diseases. Moreover, we highlight how the morphology, size, density of peptide and the protein corona influence the biological activity, biodistribution and biological fate of peptide-AuNP conjugates. In the end, we discuss the future outlook and the challenges being faced in the clinical translation of the peptide-AuNP conjugates. Overall, this review emphasizes that the peptide-AuNP conjugates might be used as potential theranostic agents for the treatment of life-threatening diseases in an economical fashion in the future.

Single-Particle Tracking with Scattering-Based Optical Microscopy

Different from traditional ensemble measurement methods, single-particle tracking (SPT) is a powerful approach to study the distribution of dynamic processes in a complex environment, providing crucial information from individual objects. This Feature summarizes the optical microscopic techniques and data analysis methods for scattering-based SPT. Some essential SPT-based applications within the cell are also delineated.

Bioactive Polysaccharide Nanoparticles Improve Radiation-Induced Abscopal Effect through Manipulation of Dendritic Cells

Radiotherapy was considered to induce an abscopal effect initiated through antigen release and presented by dendritic cells (DC), while the immunosuppressive tumor microenvironment (TEM) attenuated the effects. Herein, we utilized bioactive polysaccharides extracted from the natural herb Astragalus membranaceus and developed polysaccharide nanoparticles (ANPs) that can reverse TEM and, accordingly, enhance the radiation-induced abscopal effect. ANP showed ability to prolong the survival rate of tumor-bearing mice. In addition, ANP dramatically inhibited the growth of the primary tumor subjected to radiation as well as the secondary tumor distant from the primary lesion. Mechanistic study demonstrated that an ANP-induced immune response was mainly reflected by DC activation, represented by phenotypic maturation and enhanced antigen presentation through the TLR4 signaling pathway. Mature DC induced by ANP migrated to the tumor-draining lymph node and initiated T-cell expansion. Specifically, DC activation was successfully translated into an increase in CD4⁺ T/T_reg and CD8⁺ T/T_reg ratios within both primary (irradiated) and secondary (unirradiated) tumors. Our results also indicated that the systemic antitumor immune response and immune memory were enhanced with the increase in IFN-γ production and effector memory T-cell population. Our work provided a novel strategy to facilitate the incorporation of immunoactive macromolecules purified from natural herbs into modern nanotechnology in the era of immunotherapy.

Molecular and living cell dynamic assays with optical microscopy imaging techniques

Generally, the message elucidated by the conventional analytical methods overlooks the heterogeneity of single objects, where the behavior of individual molecules is shielded. With the advent of optical microscopy imaging techniques, it is possible to identify, visualize and track individual molecules or nanoparticles under a biological environment with high temporal and spatial resolution. In this work, we summarize the commonly adopted optical microscopy techniques for bio-analytical assays in living cells, including total internal reflection fluorescence microscopy (TIRFM), super-resolution optical microscopy (SRM), and dark-field optical microscopy (DFM). The basic principles of these methods and some recent interesting applications in molecular detection and single-particle tracking are introduced. Moreover, the development in high-dimensional optical microscopy to achieve three-dimensional (3-D) as well as sub-diffraction localization and tracking of biomolecules is also highlighted.

Single-particle tracking discloses binding-mediated rocking diffusion of rod-shaped biological particles on lipid membranes

Interestingly, on the lipid membrane, E.coli displays anomalous rocking diffusion, which might facilitate the subsequent survey of stronger association sites on the two-dimensional (2D) surface.

It has been demonstrated that rod-shaped particles can achieve a high translocation efficiency for gene and drug delivery in biological samples. Previous theoretical calculations also confirmed that rod-shaped particles display higher diffusivity than their spherical counterparts in biological porous media. Understanding the diffusion dynamics of biological and non-biological rod-shaped particles in biological solutions as well as close to the lipid membrane is therefore fundamentally significant for the rational design of efficient cargos. With dark-field optical microscopy, the translational and three-dimensional (3D) orientational diffusion dynamics of individual rod-shaped particles (i.e., E. coli and upconversion microrods, UCMRs) in phosphate buffered saline (PBS) and on the lipid membrane are tracked at the single-particle level. In the buffer solution, faster rotation of E. coli in the z direction was observed even though its dynamics in the x–y plane is comparable with that of UCMRs. Interestingly, on the lipid membrane, distinct from the confined motion of UCMRs, anomalous rocking diffusion was observed, which might facilitate the subsequent survey of stronger association sites on the two-dimensional (2D) surface. These results would afford deep insight into the better understanding of the translocation mechanism by using rod-shaped particles as a delivery cargo in biological samples.

Peptide-functionalized gold nanoparticles: versatile biomaterials for diagnostic and therapeutic applications

Colloidal gold solutions have been used for centuries in a wide variety of applications including staining glass and in the colouring of ceramics. More recently, gold nanoparticles (GNPs) have been studied extensively due to their interesting size-dependent electronic and optical properties. GNPs can be functionalized easily with biomolecules that contain thiols, amines, or even phosphine moieties. For example, the reaction of thiol-containing peptides with GNPs has been used extensively to prepare novel hybrid materials for biomedical applications. A range of different types of peptides can be used to access biomaterials that are designed to perform a specific role such as cancer cell targeting. In addition, specific peptide sequences that are responsive to external stimuli (e.g. temperature or pH) can be used to stabilise/destabilise the aggregation of colloidal GNPs. Such systems have exciting potential applications in the field of colorimetric sensing (including bio-sensing) and in targeted drug delivery platforms. In this review, we will give an overview of the current methods used for preparing peptide functionalized GNPs, and we will discuss their key properties outlining the various applications of this class of biomaterial. In particular, the potential applications of peptide functionalized GNPs in areas of sensing and targeted drug delivery will be discussed.

A study of the diffusion dynamics and concentration distribution of gold nanospheres (GNSs) without fluorescent labeling inside live cells using fluorescence single particle spectroscopy

Colloidal gold nanospheres (GNSs) have become important nanomaterials in biomedical applications due to their special optical properties, good chemical stability, and biocompatibility. However, measuring the diffusion coefficients or concentration distribution of GNSs within live cells accurately without any extra fluorescent labeling in situ has still not been resolved. In this work, a single particle method is developed to study the concentration distribution of folic acid-modified GNSs (FA-GNSs) internalized via folate receptors, and investigates their diffusion dynamics within live cells using single particle fluorescence correlation spectroscopy (FCS). We optimized the experimental conditions and verified the feasibility of 30 nm GNSs without extra fluorescence labeling being used for single particle detection inside live cells. Then, the FCS characterization strategy was used to measure the concentration and diffusion coefficient distributions of GNSs inside live cells and the obtained results were basically in agreement with those obtained by TEM. The results demonstrate that our strategy is characterized as an in situ, nondestructive, rapid and dynamic method for the assay of live cells, and it may be widely used in the further design of GNP-based drug delivery and therapeutics.

Fabrication of Positively Charged Fluorescent Polymer Nanoparticles for Cell Imaging and Gene Delivery

Development of efficient non-viral gene delivery vector has aroused great attention in the past few decades. In this study, we reported a new gene delivery vector, positively charged fluorescent conjugated polymer nanoparticles (CPNPs), for efficient gene transfection and in-situ intracellular fluorescence imaging. The microscopic and spectroscopic characterizations demonstrated that these CPNPs possess decent fluorescence performance (e.g. with fluorescence quantum yield of 70.7±0.3%) and small size dimension of ~3.6±0.3 nm (DLS result). Fast and efficient cellular translocation capability was observed according to the time-dependent living cell imaging experiments. Nearly all of the cells were loaded with CPNPs after co-incubation for 2 h regardless of the cell type. In comparison with the commonly used gene delivery vector, lipofectamine 2000 (with gene transfection efficiency of 55±5% for pEGFP), the gene expression efficiency with the positively charged CPNPs (70±3% for pEGFP) was improved significantly. Intracellular fluorescence imaging results demonstrated that the CPNPs could actively assemble close to the periphery of nuclei. Disassembly was not observed even 36 h later, which greatly facilitates releasing of pDNA close to the periphery of nuclei and thus promotes the gene transfection efficiency.

Spider Toxin Peptide Lycosin-I Functionalized Gold Nanoparticles for in vivo Tumor Targeting and Therapy

Cell penetrating peptides (CPPs) are commonly utilized for intracellular delivery of functional materials to circumvent biomembrane barrier. However, further application of CPPs is hindered by lacking selectivity toward targeted cells. The spider venom peptide, lycosin-I, is a CPP with potent cytotoxicity to cancer cells, which might enable lycosin-I to deliver functional materials into cancer cells selectively. In this study, we demonstrated that the lycosin-I-conjugated spherical gold nanoparticles (LGNPs) not only exhibited efficient cellular internalization efficiency toward cancer cells but also displayed unprecedented selectivity over noncancerous cells. Although LGNPs were removed from the living circulatory system via reticuloendothelial system-dominant clearance modes without noticeable adverse effects to animals, they actually displayed active tumor-targeting effects and efficient accumulation in tumors in vivo. Furthermore, the potential application of this platform for cancer therapy was explored by lycosin-I-conjugated gold nanorods (LGNRs). LGNRs exhibited selective intracellular translocation towards cancer cells and efficient photothermal effect under near infrared (NIR, 808 nm) irradiation, which consequently killed cancer cells in vitro and in vivo effectively. Therefore, the established LGNPs and LGNRs possessed great potential in cancer-targeting delivery and photothermal therapy.

Intracellular imaging of quantum dots, gold, and iron oxide nanoparticles with associated endocytic pathways

Metallic nanoparticles (NP) have been used for biomedical applications especially for imaging. Compared to nonmetallic NP, metallic NP provide high contrast images because of their optical light scattering, magnetic resonance, X-ray absorption, or other physicochemical properties. In this review, a series of in vitro imaging techniques for metallic NP will be introduced, meanwhile their strengths and weaknesses will be discussed. By utilizing these imaging methods, the cellular uptake of metallic NP can be easily visualized to better understand the endocytic mechanisms of NP intracellular delivery. Several types of metallic NP that are used for imaging or as contrast agents such as quantum dots, gold, iron oxide, and other metallic NP will be presented. Cellular uptake of metallic NP and associated endocytic mechanisms highly depends upon the NP size, charge, surface coating, shape, or other factors such as cell type, cell differentiation status, cell surface status, external forces, protein binding, temperature, and the biological milieu. Classical endocytic routes such as lipid raft-mediated pathways, clathrin or caveolae-mediated pathways, macropinocytosis, and phagocytosis have been investigated, yet there is still a demand to determine other endocytic pathways. Knowing the different methodologies used to determine the endocytic pathways will increase the understanding of NP toxicity, cancer cell targeting, and imaging, so that surface coatings can be created for efficient cell uptake of metallic NP with minimal cytotoxicity WIREs Nanomed Nanobiotechnol 2017, 9:e1419. doi: 10.1002/wnan.1419 For further resources related to this article, please visit the WIREs website.

Single Particle Dynamic Imaging and Fe3+ Sensing with Bright Carbon Dots Derived from Bovine Serum Albumin Proteins

In this work, we demonstrated a convenient and green strategy for the synthesis of highly luminescent and water-soluble carbon dots (Cdots) by carbonizing carbon precursors, i.e., Bovine serum albumin (BSA) nanoparticles, in water solution. Without post surface modification, the as-synthesized Cdots exhibit fluorescence quantum yield (Q.Y.) as high as 34.8% and display superior colloidal stability not only in concentrated salt solutions (e.g. 2 M KCl) but also in a wide range of pH solutions. According to the FT-IR measurements, the Cdots contain many carboxyl groups, providing a versatile route for further chemical and biological functionalization. Through conjugation of Cdots with the transacting activator of transcription (TAT) peptide (a kind of cell penetration peptide (CPP)) derived from human immunodeficiency virus (HIV), it is possible to directly monitor the dynamic interactions of CPP with living cell membrane at single particle level. Furthermore, these Cdots also exhibit a dosage-dependent selectivity toward Fe³⁺ among other metal ions, including K⁺, Na⁺, Mg²⁺, Hg²⁺, Co²⁺, Cu²⁺, Pb²⁺ and Al³⁺. We believed that the Cdots prepared by this strategy would display promising applications in various areas, including analytical chemistry, nanomedicine, biochemistry and so on.

Ligand-Modified Human Serum Albumin Nanoparticles for Enhanced Gene Delivery

The development of nonviral gene delivery systems is a great challenge to enable safe gene therapy. In this study, ligand-modified nanoparticles based on human serum albumin (HSA) were developed and optimized for an efficient gene therapy. Different glutaraldehyde cross-linking degrees were investigated to optimize the HSA nanoparticles for gene delivery. The peptide sequence arginine-glycine-aspartate (RGD) and the HIV-1 transactivator of transduction sequence (Tat) are well-known as promising targeting ligands. Plasmid DNA loaded HSA nanoparticles were covalently modified on their surface with these different ligands. The transfection potential of the obtained plasmid DNA loaded RGD- and Tat-modified nanoparticles was investigated in vitro, and optimal incubation conditions for these preparations were studied. It turned out that Tat-modified HSA nanoparticles with the lowest cross-linking degree of 20% showed the highest transfection potential. Taken together, ligand-functionalized HSA nanoparticles represent promising tools for efficient and safe gene therapy.