Determination of the Absolute Number Concentration of Nanoparticles and the Active Affinity Sites on Their Surfaces

Kinetic Processes in Enzymatic Nanoreactors for In Vivo Detoxification

Enzymatic nanoreactors are enzyme-encapsulated nanobodies that are capable of performing biosynthetic or catabolic reactions. For this paper, we focused on therapeutic enzyme nanoreactors for the neutralization of toxicants, paying special attention to the inactivation of organophosphorus compounds (OP). Therapeutic enzymes that are capable of detoxifying OPs are known as bioscavengers. The encapsulation of injectable bioscavengers by nanoparticles was first used to prevent fast clearance and the immune response to heterologous enzymes. The aim of enzyme nanoreactors is also to provide a high concentration of the reactive enzyme in stable nanocontainers. Under these conditions, the detoxification reaction takes place inside the compartment, where the enzyme concentration is much higher than in the toxicant diffusing across the nanoreactor membrane. Thus, the determination of the concentration of the encapsulated enzyme is an important issue in nanoreactor biotechnology. The implications of second-order reaction conditions, the nanoreactor’s permeability in terms of substrates, and the reaction products and their possible osmotic, viscosity, and crowding effects are also examined.

Absolute quantification of particle number concentration using a digital single particle counting system

The accurate determination of the molar concentration or the number concentration of particles in a defined volume is important but challenging. Since particle diversity and heterogeneity cannot be ignored in particle quantification, single particle counting has become quite important. However, most methods require standard samples (calibrators) which are usually difficult to obtain. The authors describe a method for single particle counting that is based on the combination of digital counting and formation of microdroplets in a microchip. By compartmentalizing particles into picoliter droplets, positive droplets encapsulating particles were counted and particle concentrations were calculated by Poisson statistics. The concentration of particles over a wide range (from 5.0 × 10³ to 1.8 × 10⁷ particles per mL) were accurately determined without the need for using a calibrator. A microdroplet chip including a T-junction channel achieved a 9-fold increase of signal-to-background ratio compared to the traditional flow-focusing chip. This makes the digital counting system a widely applicable tool for quantification of fluorescent particles. Various particles including differently sized fluorescent microspheres and bacteria with large heterogeneity in shape such as Escherichia coli DH5α-pDsRed were accurately quantified by this method. Graphical abstract Schematic representation of the digital single particle counting system for absolute quantification of particles. Particles compartmentalized in picoliter droplets were counted and the number concentration of particles was determined using digital analysis.

Cell Membrane-Camouflaged NIR II Fluorescent Ag2 Te Quantum Dots-Based Nanobioprobes for Enhanced In Vivo Homotypic Tumor Imaging

The advantages of fluorescence bioimaging in the second near-infrared (NIR II, 1000-1700 nm) window are well known; however, current NIR II fluorescent probes for in vivo tumor imaging still have many shortcomings, such as low fluorescence efficiency, unstable performance under in vivo environments, and inefficient enrichment at tumor sites. In this study, Ag₂ Te quantum dots (QDs) that emit light at a wavelength of 1300 nm are assembled with poly(lactic-co-glycolic acid) and further encapsulated within cancer cell membranes to overcome the shortcomings mentioned above. The as-prepared ≈100 nm biomimetic nanobioprobes exhibit ultrabright (≈60 times greater than that of free Ag₂ Te QDs) and highly stable (≈97% maintenance after laser radiation for 1 h) fluorescence in the NIR II window. By combining the active homotypic tumor targeting capability derived from the source cell membrane with the passive enhanced permeation and retention effect, improved accumulation at tumor sites ((31 ± 2)% injection dose per gram of tumor) and a high tumor-to-normal tissue ratio (13.3 ± 0.7) are achieved. In summary, a new biomimetic NIR II fluorescent nanobioprobe with ultrabright and stable fluorescence, homotypic targeting and good biocompatibility for enhanced in vivo tumor imaging is developed in this study.

Magnetic nanospheres for convenient and efficient capture and release of hepatitis B virus DNA

Nucleic acid isolation and purification are essential steps in molecular biology. Currently-used isolation methods focus on the extraction of all the nucleic acids from crude samples, yet ignore the specific nucleic acids of interest, which may induce the loss of the specific nucleic acids and hinder their analyses. Herein, a magnetic nanospheres (MNs)-based strategy for efficient capture and release of specific nucleic acids is developed. The DNA sequence of hepatitis B virus (HBV) is taken as a model to validate this method. The MNs are modified with the complementary strand of HBV DNA for specific capture based on hybridization reaction. Then, by melting at high temperature, the captured DNAs are detached from the MNs to achieve release. The capture and release process are performed conveniently with magnetic separation. High capture efficiency (over 80%) and nearly 100% release efficiency for HBV DNA are achieved respectively via 40 min and 5 min interaction. While non-target DNAs are hardly captured, indicative of good selectivity. Moreover, after releasing DNAs, the MNs are directly regenerated and can be reused without degrading performance, which greatly reduces the operation costs. Finally, this method is applied to serum samples without any pretreatment, which exhibits similar capture and release capacity with those in the ideal samples, indicating its great application potential in practice.

Nanoparticle heterogeneity: an emerging structural parameter influencing particle fate in biological media?

Drug nanocarriers' surface chemistry is often presumed to be uniform. For instance, the polymer surface coverage and distribution of ligands on nanoparticles are described with averaged values obtained from quantification techniques based on particle populations. However, these averaged values may conceal heterogeneities at different levels, either because of the presence of particle sub-populations or because of surface inhomogeneities, such as patchy surfaces on individual particles. The characterization and quantification of chemical surface heterogeneities are tedious tasks, which are rather limited by the currently available instruments and research protocols. However, heterogeneities may contribute to some non-linear effects observed during the nanoformulation optimization process, cause problems related to nanocarrier production scale-up and correlate with unexpected biological outcomes. On the other hand, heterogeneities, while usually unintended and detrimental to nanocarrier performance, may, in some cases, be sought as adjustable properties that provide NPs with unique functionality. In this review, results and processes related to this issue are compiled, and perspectives and possible analytical developments are discussed.

Intracameral Delivery of Layer-by-Layer Coated siRNA Nanoparticles for Glaucoma Therapy

Glaucoma is the second leading cause of blindness worldwide, often associated with elevated intraocular pressure. Connective tissue growth factor (CTGF) is a mediator of pathological effects in the trabecular meshwork (TM) and Schlemm's canal (SC). A novel, causative therapeutic concept which involves the intracameral delivery of small interfering RNA against CTGF is proposed. Layer-by-layer coated nanoparticles of 200-260 nm with a final layer of hyaluronan (HA) are developed. The HA-coating should provide the nanoparticles sufficient mobility in the extracellular matrix and allow for binding to TM and SC cells via CD44. By screening primary TM and SC cells in vitro, in vivo, and ex vivo, the validity of the concept is confirmed. CD44 expression is elevated in glaucomatous versus healthy cells by about two- to sixfold. CD44 is significantly involved in the cellular uptake of HA-coated nanoparticles. Ex vivo organ culture of porcine, murine, and human eyes demonstrates up to threefold higher accumulation of HA compared to control nanoparticles and much better penetration into the target tissue. Gene silencing in primary human TM cells results in a significant reduction of CTGF expression. Thus, HA-coated nanoparticles combined with RNA interference may provide a potential strategy for glaucoma therapy.

Methods for improving the immunogenicity and efficacy of cancer vaccines

INTRODUCTION

Cancer vaccines represent one of the oldest immunotherapy strategies. A variety of tumor-associated antigens have been exploited to investigate their immunogenicity as well as multiple strategies for vaccine administration. These efforts have led to the development of several clinical trials in tumors with different histological origins to test the clinical efficacy of cancer vaccines. However, suboptimal clinical results have been reported mainly due to the lack of optimized strategies to induce strong and sustained systemic tumor antigen-specific immune responses.

AREAS COVERED

We provide an overview of different types of cancer vaccines that have been developed and used in the context of clinical studies. Moreover, we review different preclinical and clinical strategies pursued to enhance the immunogenicity, stability, and targeting at tumor site of cancer vaccines.

EXPERT OPINION

Additional and appropriate preclinical studies are warranted to optimize the immunogenicity and delivery of cancer vaccines. The appropriate choice of target antigens is challenging; however, the exploitation of neoantigens generated from somatic mutations of tumor cells represents a promising approach to target highly immunogenic tumor-specific antigens. Remarkably, the investigation of the combination of cancer vaccines with immunomodulating agents able to skew the tumor microenvironment from immunosuppressive to immunostimulating will dramatically improve their clinical efficacy.

Aptamer-functionalized magnetic and fluorescent nanospheres for one-step sensitive detection of thrombin

A one-step sandwich method is described for detecting proteins with magnetic nanospheres (MNs) and fluorescent nanospheres (FNs). Thrombin is selected as a model analyte to validate the method. Two DNA aptamers (Apt 29 and Apt 15 targeting two different exosites of thrombin) are chosen as recognition elements to modify MNs and FNs. The superparamagnetic MN-Apt 29 conjugate is used to separate and concentrate thrombin. The FN-Apt 15 conjugate encapsulates hundreds of fluorescent quantum dots and is used as reporter to provide a stable signal. Magnetic capture and fluorescence identification are performed simultaneously to form a sandwich complex (MN-Apt 29-thrombin-FN-Apt 15) for fluorescence determination (at excitation/emission wavelengths of 380/622 nm). The method is convenient, time saving, and gives a strong signal (compared to the two-step method where capture and identification are performed in two steps). The one-step method presented here is completed within 30 min and has a 3.5 ng·mL^-1 (97 pM) detection limit. The method is reproducible, has an intra-assay variability of 1.5%, and an inter-assay variability of 4.9%. Other serum proteins (HSA, CEA, PSA, and AFP) do not interfere. The method was also applied to analyze serum samples. Almost the same fluorescence intensity was measured when analyzing 1% serum samples (compared to buffer samples). Graphical abstract Magnetic nanospheres with excellent superparamagnetic property and fluorescent QD-based nanospheres were prepared and used in a one-step sensitive method for detecting thrombin. The method exhibits good reproducibility, high specificity, and good selectivity.

Efficient Enrichment and Analyses of Bacteria at Ultralow Concentration with Quick-Response Magnetic Nanospheres

Enrichment and purification of bacteria from complex matrices are crucial for their detection and investigation, in which magnetic separation techniques have recently show great application advantages. However, currently used magnetic particles all have their own limitations: Magnetic microparticles exhibit poor binding capacity with targets, while magnetic nanoparticles suffer slow magnetic response and high loss rate during treatment process. Herein, we used a highly controllable layer-by-layer assembly method to fabricate quick-response magnetic nanospheres (MNs), and with Salmonella typhimurium as a model, we successfully achieve their rapid and efficient enrichment. The MNs combined the advantages of magnetic microparticles and nanoparticles. On the one hand, the MNs had a fast magnetic response, and almost 100% of the MNs could be recovered by 1 min attraction with a simple magnetic scaffold. Hence, using antibody conjugated MNs (immunomagnetic nanospheres, IMNs) to capture bacteria hardly generated loss and did not need complex separation tools or techniques. On the other hand, the IMNs showed much excellent capture capacity. With 20 min interaction, almost all of the target bacteria could be captured, and even only one bacterium existing in the samples was not missed, comparing with the immunomagnetic microparticles which could only capture less than 50% of the bacteria. Besides, the IMNs could achieve the same efficient enrichment in complex matrices, such as milk, fetal bovine serum, and urine, demonstrating their good stability, strong anti-interference ability, and low nonspecific adsorption. In addition, the isolated bacteria could be directly used for culture, polymerase chain reaction (PCR) analyses, and fluorescence immunoassay without a release process, which suggested our IMNs-based enrichment strategy could be conveniently coupled with the downstream identification and analysis techniques. Thus, the MNs provided by this work showed great superiority in bacteria enrichment, which would be a promising tool for bacteria detection and investigation.