Effective reduction of nonspecific binding by surface engineering of quantum dots with bovine serum albumin for cell-targeted imaging

Effect of PVP Molecular Weights on the Synthesis of Ultrasmall Cus Nanoflakes: Synthesis, Properties, and Potential Application for Phototheranostics

Copper sulfide nanoparticles (CuS) hold tremendous potential for applications in photothermal therapy (PTT) and photoacoustic imaging (PAI). However, the conventional chemical coprecipitation method often leads to particle agglomeration issues. To overcome this challenge, we utilized polyvinylpyrrolidone (PVP) as a stabilizing agent, resulting in the synthesis of small PVP-CuS nanoparticles named PC10, PCK30, and PC40. Our study aimed to investigate how different molecular weights of PVP influence the nanoparticles' crystalline characteristics and essential properties, especially their photoacoustic and photothermal responses. While prior research on PVP-assisted CuS nanoparticles has been conducted, our study delves deeper into this area, providing insights into optical properties. Remarkably, all synthesized nanoparticles exhibited a crystalline structure, were smaller than 10 nm, and featured an absorbance peak at 1020 nm, indicating their robust photoacoustic and photothermal capabilities. Among these nanoparticles, PC10 emerged as the standout performer, displaying superior photoacoustic properties. Our photothermal experiments demonstrated significant temperature increases in all cases, with PC10 achieving an impressive efficiency of 51%. Moreover, cytotoxicity assays revealed the nanoparticles' compatibility with cells, coupled with an enhanced incidence of apoptosis compared to necrosis. These findings underscore the promising potential of PVP-stabilized CuS nanoparticles for advanced cancer theranostics.

Compact and modular bioprobe: Integrating SpyCatcher/SpyTag recombinant proteins with zwitterionic polymer-coated quantum dots

The development of quantum dot (QD)-based modular bioprobe that has a compact size and enable a facile conjugation of various biofunctional groups is in high demand. To address this, we surface engineered QDs with zwitterion polymer ligands to have an inherent compact size and derivatized them sequentially with the recombinant proteins SpyCatcher/SpyTag (SC/ST) to use their protein ligation system. SC/ST spontaneously form one complex through the isopeptide bond between them. SC-conjugated QDs (QD-SC) were used as base building blocks. Then, ST-biomolecules were added for modular biofunctionalization. We synthesized compact sized (∼15 nm) QD-SC-ST-affibody (antibody-mimicking small protein for tumor detection) conjugates, which showed successful cell-receptor targeting. The target cell-receptor could be easily tuned by changing the type of ST-affibody. We also demonstrated that anti-human-chorionic-gonadotropin mouse IgG1 antibodies can be labeled on the QD surface by mixing QD-SC with the ST-MG1Nb (mouse-IgG1-specific protein). The immunoassay performance of the antibody-labeled QDs was evaluated using a pregnancy test kit, displaying equivalent detection sensitivity to a commercially available kit. This study proposed an innovative strategy for QD biofunctionalization in a modular manner, which can be expanded to a diverse range of colloidal particle derivatization.

Integrating Synthesis, Physicochemical Characterization, and In Silico Studies of Cordycepin-Loaded Bovine Serum Albumin Nanoparticles

Cordycepin gets rapidly metabolized in the body into inactive form due to its structural similarity to adenosine, thus inhibiting its development as a medicinal agent. This study was aimed to improve the solubility and stability of cordycepin, a potential drug with known antiproliferative activity, by encapsulating it in bovine serum albumin: β-cyclodextrin nanoparticles. Cordycepin-loaded nanoparticles (CLNPs) were synthesized using the antisolvent method and characterized thoroughly using various techniques. Our dynamic light scattering measurement showed a particle size and zeta potential of 160 ± 2.75 nm and -20.21 ± 2.1 mV, respectively, for CLNPs. Transmission electron microscopy studies revealed that particles were spherical in morphology. These CLNPs showed sustained release of cordycepin with encapsulation and loading efficiency of 81.62 ± 1.5 and 27.02 ± 2.0%, respectively, based on high-performance liquid chromatography and UV-vis studies. Based on differential scanning calorimetry and zeta potential studies, CLNPs improve cordycepin stability and solubility. Our molecular simulations and binding energy calculation also showed favorable protein interaction between cordycepin, bovine serum albumin, and β-cyclodextrin, further supporting the notion of improved stability. In vitro cytotoxicity, apoptosis, and cellular uptake studies on breast cancer cells showed that the synthesized nanoparticles had greater cytotoxicity as compared to free cordycepin.

Recent advances in measurement of metabolic clearance, metabolite profile and reaction phenotyping of low clearance compounds

INTRODUCTION

Low metabolic clearance is usually a highly desirable property of drug candidates in order to reduce dose and dosing frequency. However, measurement of low clearance can be challenging in drug discovery. A number of new tools have recently been developed to address the gaps in the measurement of intrinsic clearance, identification of metabolites, and reaction phenotyping of low clearance compounds.

AREAS COVERED

The new methodologies of low clearance measurements are discussed, including the hepatocyte relay, HepatoPac®, HμREL®, and spheroid systems. In addition, metabolite formation rate determination and in vivo allometric scaling approaches are covered as alternative methods for low clearance measurements. With these new methods, measurement of ~ 20-fold lower limit of intrinsic clearance can be achieved. The advantages and limitations of each approach are highlighted.

EXPERT OPINION

Although several novel methods have been developed in recent years to address the challenges of low clearance, these assays tend to be time and labor intensive and costly. Future innovations focusing on developing systems with high enzymatic activities, ultra-sensitive universal quantifiable detectors, and artificial intelligence will further enhance our ability to explore the low clearance space.

Clinical Application of Epithelial Sodium Channel (ENaC) as a Biomarker for Arterial Hypertension

Arterial hypertension (HTN) is a global public health concern and an important risk factor for cardiovascular diseases and renal failure. We previously reported overexpression of ENaC on the plasma membrane of human platelets is a hallmark of HTN. In this double-blinded study of an open population (n = 167), we evaluated the sensitivity and specificity of a diagnostic assay based on gold nanoparticles (AuNPs) conjugated to an antibody against epithelial sodium channel (ENaC) expressed on platelets, which is detected using a fluorescent anti-ENaC secondary antibody and spectrofluorometry. Using the cutoff value for the AuNP-anti-ENaC assay, we confirmed the diagnosis for 62.1% of patients with clinical HTN and detected 59.7% of patients had previously undiagnosed HTN. Although some shortcomings in terms of accurately discriminating healthy individuals and patients with HTN still need to be resolved, we propose this AuNP-anti-ENaC assay could be used for initial screening and early diagnosis to critically improve opportune clinical management of HTN.

Permeation of albumin through the skin depending on its concentration and the substrate used in simulated conditions in vivo

OBJECTIVE

Many drugs applied to the skin with a systemic effect do not have a therapeutic effect, due to the barrier posed by the complex structure of the skin. To counteract this, absorption promoters are often added to the drug formulation. The use of albumin as an effective drug carrier is increasingly being addressed. Albumin, a natural, non-toxic polymer, can target drugs to specific cells and extend their biological half-life. This study was designed to trace the permeation of albumin after topical administration to the skin as a potential carrier of therapeutic substances.

MATERIALS AND METHODS

Four dermal formulations based on different polymers were prepared: methyl cellulose, sodium alginate, hypromellose and chitosan with methyl cellulose, obtaining final concentrations of albumin of 2%, 1.5% and 1%. The permeation of albumin through the skin was examined under simulated in vivo conditions.

RESULTS

Most albumin permeated from the methylcellulose-based hydrogel. Depending on the concentration of albumin, permeation profiles were plotted and permeation rate constant and AUC_(0-24 h) were calculated.

CONCLUSION

Methylcellulose was the optimal polymer for albumin release, whereas hypromellose was the least favorable. The concentration of albumin influences the amount and rate of permeation of this protein. The optimal concentration was 10 mg/g, from which the most albumin penetrated and the fastest. Human skin appeared to be more permeable to albumin than pig skin. However, the similar permeation profile through both membranes successfully allows the use of pig skin to track and evaluate the permeation of therapeutic substances with systemic effects.

Realization of a Model-Free Pathway for Quantum Dot-Protein Interaction Beyond Classical Protein Corona or Protein Complex

Although in recent times nanoparticles (NPs) are being used in various biological applications, their mechanism of binding interactions still remains hazy. Usually, the binding mechanism is perceived to be mediated through either the protein corona (PC) or protein complex (PCx). Herein, we report that the nanoparticle (NP)-protein interaction can also proceed via a different pathway without forming the commonly observed PC or PCx. In the present study, the NP-protein interaction between less-toxic zinc-silver-indium-sulfide (ZAIS) quantum dots (QDs) and bovine serum albumin (BSA) was investigated by employing spectroscopic and microscopic techniques. Although the analyses of data obtained from fluorescence and thermodynamic studies do indicate the binding between QDs and BSA, they do not provide clear experimental evidence in favor of PC or PCx. Quite interestingly, high-resolution transmission electron microscopy (HRTEM) studies have shown the formation of a new type of species where BSA protein molecules are adsorbed onto some portion of a QD surface rather than the entire surface. To the best of our knowledge, we believe that this is the first direct experimental evidence in favor of a model-free pathway for NP-protein interaction events. Thus, the outcome of the present study, through experimental evidence, clearly suggests that NP-protein interaction can proceed by following a pathway that is different from classical PC and PCx.

Biomolecular Surface Functionalization and Stabilization Method to Fabricate Quantum Dots Nanobeads for Accurate Biosensing Detection

The surface functionalization of quantum dots (QDs) is essential for their application as a label material in a biological field. Here, a protein surface functionalization approach was introduced to combine with silica encapsulation for the sustainable and stable synthesis of QDs nanobeads for biomarker detection. The formation of QDs nanobeads was achieved by multiple mercapto groups in bovine serum albumin (BSA) macromolecules as multidentate ligands to replace hydrophobic ligands on the surface of QDs and decompression. The resulting QDs nanobeads exhibited 20 times more photoluminescence than the corresponding hydrophobic QDs and presented excellent stability under physiological conditions due to the protection of BSA and silica. The nanobeads served as a robust signal-generating reagent to construct the lateral flow immunoassay (LFIA) biosensor for the detection of glycosylated hemoglobin (HbA1c). The concentration of HbA1c was determined within 10 min with high specificity using only 60 μL of whole blood samples collected clinically. The nanobeads-based LFIA biosensor exhibited linear detection of HbA1c from 4.2% to 13.6%. The accuracy and stability of this approach in clinical utility was demonstrated by the detection of HbA1c after a long-term storage of test strips. This protein surface modification technology provides a new way for improving the biological properties of QDs in clinical diagnosis.

InP-Bovine Serum Albumin Conjugates as Energy Transfer Probes

The use of indium phosphide (InP) quantum dots (QDs) as biological fluorophores is limited by the low photoluminescence quantum yield (ϕ_PL) and the lack of effective bioconjugation strategies. The former issue has been addressed by introducing a strain relaxing intermediate shell such as ZnSe, GaP etc. that significantly enhances the ϕ_PL of InP. Herein, we present an effective strategy for the conjugation of emissive InP/GaP/ZnS QDs with a commonly used globular protein, namely bovine serum albumin (BSA), which generate colloidally stable QD bioconjugates, labeled as InP-BSA and demonstrate its use as energy transfer probes. The conjugate contains one protein per QD, and the circular dichroism spectra of BSA and InP-BSA exhibit similar fractions of α-helix and β-sheet, reflective of the fact that the secondary structure of the protein is intact on binding. More importantly, the fluorescence polarization studies corroborate the fact that the bound protein can hold a variety of chromophoric acceptors. Upon selectively exciting the InP-BSA component in the presence of bound chromophores, a reduction in the emission intensity of the donor is observed with a concomitant increase in emission of the acceptor. Time-resolved investigations further confirm an efficient nonradiative energy transfer from InP-BSA to the bound acceptors.

Targeting cell surface glycans with lectin-coated fluorescent nanodiamonds

Glycosylation is arguably the most important functional post-translational modification in brain cells and abnormal cell surface glycan expression has been associated with neurological diseases and brain cancers. In this study we developed a novel method for uptake of fluorescent nanodiamonds (FND), carbon-based nanoparticles with low toxicity and easily modifiable surfaces, into brain cell subtypes by targeting their glycan receptors with carbohydrate-binding lectins. Lectins facilitated uptake of 120 nm FND with nitrogen-vacancy centers in three types of brain cells - U87-MG astrocytes, PC12 neurons and BV-2 microglia cells. The nanodiamond/lectin complexes used in this study target glycans that have been described to be altered in brain diseases including sialic acid glycans via wheat (Triticum aestivum) germ agglutinin (WGA), high mannose glycans via tomato (Lycopersicon esculentum) lectin (TL) and core fucosylated glycans via Aleuria aurantia lectin (AAL). The lectin conjugated nanodiamonds were taken up differently by the various brain cell types with fucose binding AAL/FNDs taken up preferentially by glioblastoma phenotype astrocyte cells (U87-MG), sialic acid binding WGA/FNDs by neuronal phenotype cells (PC12) and high mannose binding TL/FNDs by microglial cells (BV-2). With increasing recognition of glycans having a role in many diseases, the lectin bioconjugated nanodiamonds developed here are well suited for further investigation into theranostic applications.

Label-Free and Highly-Sensitive Detection of Ochratoxin A Using One-Pot Synthesized Reduced Graphene Oxide/Gold Nanoparticles-Based Impedimetric Aptasensor

Ochratoxin A (OTA) primarily obtained by the genera aspergillus and penicillium, is one of the toxic substances for different organs and systems of the human body such as the kidney, liver, neurons and the immune system. Moreover, it is considered to cause tumors and fetal malformation even at a very low concentration. Fast and sensitive assay for detection of OTA at ultralow levels in foods and agricultural products has been an increasing demand. In this study, a new label-free electrochemical biosensor based on three-dimensional reduced graphene oxide/gold nanoparticles/aptamer for OTA detection was constructed. The 3D-rGO/Au NPs nanocomposites were firstly synthesized using a one-pot hydrothermal process under optimized experimental conditions. The 3D-rGO/Au NPs with considerable particular surface area and outstanding electrical conductivity was then coated on a glass carbon electrode to provide tremendous binding sites for -SH modified aptamer via the distinctive Au-S linkage. The presence of OTA was specifically captured by aptamer and resulted in electrochemical impedance spectroscopy (EIS) signal response accordingly. The constructed impedimetric aptasensor obtained a broad linear response from 1 pg/mL to 10 ng/mL with an LOD of 0.34 pg/mL toward OTA detection, highlighting the excellent sensitivity. Satisfactory reproducibility was also achieved with the relative standard deviation (RSD) of 1.393%. Moreover, the proposed aptasensor obtained a good recovery of OTA detection in red wine samples within the range of 93.14 to 112.75% along with a low LOD of 0.023 ng/mL, indicating its applicability for OTA detection in real samples along with economical, specific, susceptible, fast, easy, and transportable merits.

Magnetic Particles for CTC Enrichment

Simple Summary

For the enrichment of very rare cells, such as Circulating Tumor Cells (CTCs), immunomagnetic enrichment is frequently used. For this purpose, magnetic nanoparticles (MNPs) coated with specific antibodies directed against cancer cells are used. In this review, we look at the properties such a particle needs to have in order to be used successfully, and describe the different methods used in the production of such a particle as well as the methods for their separation. Additionally, an overview is given of the antibodies that could potentially be used for this purpose.

Abstract

Here, we review the characteristics and synthesis of magnetic nanoparticles (MNPs) and place these in the context of their usage in the immunomagnetic enrichment of Circulating Tumor Cells (CTCs). The importance of the different characteristics is explained, the need for a very specific enrichment is emphasized and different (commercial) magnetic separation techniques are shown. As the specificity of an MNP is in a large part dependent on the antibody coated onto the particle, different strategies in the coupling of specific antibodies as well as an overview of the available antibodies is given.

Bimodal size distribution immuno-quantum dots for fluorescent western blotting assay with high sensitivity and extended dynamic range

A highly sensitive quantum dot (QD)-based western blot assay with extended dynamic range was developed. Bimodal size distribution QD (BQ) immunoprobes composed of small size single QD (7.3 nm) and big size QD nanobead (QB) (82.9 nm) were employed for fluorescent western blot immunoassay on a membrane. Small size QD immunoprobes contributed to wider dynamic range of assay, while big size QB immunoprobes provided higher detection sensitivity. This BQ-based western blot assay can achieve a wide dynamic range (from 7.8 to 4000 ng IgG) and is nearly as sensitive as commercial available ultrasensitive chemiluminescent methods, just using a simple gel imager with UV light (365 nm) excitation and red light filter (610 nm). The fluorescent signals of BQ western blot were stable for 10 min, while chemiluminescent signals faded after 1 min. Moreover, this BQ immunoprobe was utilized for the detection of housekeeping protein and specific target proteins in complex cell lysate samples. The limit of detection of housekeeping protein is 0.25 μg of cell lysate, and the signal intensities were proportional to loading protein amount in a wide range from 0.61 to 80 μg. We believe that this new strategy of bimodal size distribution nanoparticles can also be expanded for other functional nanoparticle-based biological assays to improve the sensitivity and extend the dynamic range. Graphical abstract.

Zwitterion and Oligo(ethylene glycol) Synergy Minimizes Nonspecific Binding of Compact Quantum Dots

Quantum dots (QDs) are a class of fluorescent nanocrystals in development as labels for molecular imaging in cells and tissues. Recently, coatings for quantum dots based on multidentate polymers have improved labeling performance in a range of bioanalytical applications, primarily due to reduced probe hydrodynamic size. Now, an ongoing challenge is to eliminate nonspecific binding between these small probes and cellular components that mask specifically labeled molecules. Here, we describe insights into controlling and minimizing intermolecular interactions governing nonspecific binding using multidentate polymers with tunable hydrophilic functional groups that are cationic, anionic, zwitterionic (ZW), or nonionic (oligoethylene glycol; OEG). By fixing surface-binding groups and polymer length, coated colloids have similar sizes but diverse physicochemical properties. We measure binding to globular proteins, fixed cells, and living cells and observe a substantial improvement in nonspecific binding resistance when surfaces are functionalized with a combination of ZW and OEG. The independent underlying effects of counterion adsorption and flexibility appear to synergistically resist adsorption when combined, particularly for fixed cells enriched in both charged and hydrophobic moieties. We further show that ZW-OEG QDs are stable under diverse conditions and can be self-assembled with antibodies to specifically label surface antigens on living cells and cytoplasmic proteins in fixed cells. This surface engineering strategy can be adopted across the diverse range of colloidal materials currently in use and in development for biomedical applications to optimize their molecular labeling specificity.

A Tumor-Microenvironment-Activated Nanozyme-Mediated Theranostic Nanoreactor for Imaging-Guided Combined Tumor Therapy

Activatable theranostic agents that can be activated by tumor microenvironment possess higher specificity and sensitivity. Here, activatable nanozyme-mediated 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) loaded ABTS@MIL-100/poly(vinylpyrrolidine) (AMP) nanoreactors (NRs) are developed for imaging-guided combined tumor therapy. The as-constructed AMP NRs can be specifically activated by the tumor microenvironment through a nanozyme-mediated "two-step rocket-launching-like" process to turn on its photoacoustic imaging signal and photothermal therapy (PTT) function. In addition, simultaneously producing hydroxyl radicals in response to the high H₂ O₂ level of the tumor microenvironment and disrupting intracellular glutathione (GSH) endows the AMP NRs with the ability of enhanced chemodynamic therapy (ECDT), thereby leading to more efficient therapeutic outcome in combination with tumor-triggered PTT. More importantly, the H₂ O₂ -activated and acid-enhanced properties enable the AMP NRs to be specific to tumors, leaving the normal tissues unharmed. These remarkable features of AMP NRs may open a new avenue to explore nanozyme-involved nanoreactors for intelligent, accurate, and noninvasive cancer theranostics.

Magnetic Nanoclusters Coated with Albumin, Casein, and Gelatin: Size Tuning, Relaxivity, Stability, Protein Corona, and Application in Nuclear Magnetic Resonance Immunoassay

The surface functionalization of magnetic nanoparticles improves their physicochemical properties and applicability in biomedicine. Natural polymers, including proteins, are prospective coatings capable of increasing the stability, biocompatibility, and transverse relaxivity (r2) of magnetic nanoparticles. In this work, we functionalized the nanoclusters of carbon-coated iron nanoparticles with four proteins: bovine serum albumin, casein, and gelatins A and B, and we conducted a comprehensive comparative study of their properties essential to applications in biosensing. First, we examined the influence of environmental parameters on the size of prepared nanoclusters and synthesized protein-coated nanoclusters with a tunable size. Second, we showed that protein coating does not significantly influence the r2 relaxivity of clustered nanoparticles; however, the uniform distribution of individual nanoparticles inside the protein coating facilitates increased relaxivity. Third, we demonstrated the applicability of the obtained nanoclusters in biosensing by the development of a nuclear-magnetic-resonance-based immunoassay for the quantification of antibodies against tetanus toxoid. Fourth, the protein coronas of nanoclusters were studied using SDS-PAGE and Bradford protein assay. Finally, we compared the colloidal stability at various pH values and ionic strengths and in relevant complex media (i.e., blood serum, plasma, milk, juice, beer, and red wine), as well as the heat stability, resistance to proteolytic digestion, and shelf-life of protein-coated nanoclusters.

Biocompatible quantum dot-antibody conjugate for cell imaging, targeting and fluorometric immunoassay: crosslinking, characterization and applications

Quantum dots (QDs) are important fluorescent probes that offer great promise for bio-imaging research due to their superior optical properties. However, QDs for live cell imaging and the tracking of cells need more investigation to simplify processing procedures, improving labeling efficiency, and reducing chronic toxicity. In this study, QDs were functionalized with bovine serum albumin (BSA) via a chemical linker. Anti-human immunoglobulin antibodies were oxidized by sodium periodate to create reactive aldehyde groups for a spontaneous reaction with the amine groups of BSA-modified QDs. An antibody-labeled QD bioconjugate was characterized using agarose gel electrophoresis, dynamic light scattering, and zeta potential. Using fluorescence spectroscopy, we found that the fluorescence of QDs was retained after multiple conjugation steps. The cell-labeling function of the QD bioconjugate was confirmed using an image analyzer and confocal microscopy. The QD bioconjugate specifically targeted human immunoglobulin on the membrane surface of recombinant cells. In addition, the QD bioconjugate applied in fluorometric immunoassay was effective for the quantitative analysis of human immunoglobulin in an enzyme-linked immunosorbent assay. The developed QD bioconjugate may offer a promising platform to develop biocompatible tools to label cells and quantify antibodies in the immunoassay.

A layer-by-layer covalent strategy is developed including the modification of QDs using BSA as a stabilizing agent and then anti-human immunoglobulin antibody as a targeting moiety.

Development of a smartphone-based rapid dual fluorescent diagnostic system for the simultaneous detection of influenza A and H5 subtype in avian influenza A-infected patients

Accurate and rapid diagnosis of highly pathogenic avian influenza A H5N1 is of critical importance for the effective clinical management of patients. Here, we developed a rapid and simultaneous detection toolkit for influenza A H5 subtype viruses in human samples based on a bioconjugate of quantum dots (QDs) assembly and a smartphone-based rapid dual fluorescent diagnostic system (SRDFDS). Methods: Two types of QDs were assembled on a latex bead to enhance the detection sensitivity and specificity of influenza A infection (QD580) and H5 subtype (QD650). The dual signals of influenza A and H5 subtype of H5N1-infected patients were detected simultaneously and quantified separately by SRDFDS equipped with two emission filters. Results: Our results showed a high sensitivity of 92.86% (13/14) and 78.57% (11/14), and a specificity of 100% (38/38, P < 0.0001) and 97.37% (37/38) for influenza A and H5 subtype detection, respectively. Conclusion: Therefore, our multiplex QD bioconjugates and SRDFDS-based influenza virus detection toolkit potentially provide accurate and meaningful diagnosis information with improved detection accuracies and sensitivities for H5N1 patients.

In vivo tailor-made protein corona of a prodrug-based nanoassembly fabricated by redox dual-sensitive paclitaxel prodrug for the superselective treatment of breast cancer

Prodrug self-nanoassemblies have many advantages for anticancer drug delivery, including high drug loading rate, resistance to recrystallization, and on-demand drug release. However, few studies have focused on their protein corona, which is inevitably formed after entering the blood and determines their subsequent fates in vivo. To actively tune the protein corona of prodrug nanoassemblies, three maleimide-paclitaxel prodrugs were synthesized via different redox-sensitive linkers (ester bond, thioether bond and disulfide bond). After incubation with rat plasma, the surface maleimide groups effectively captured albumins, resulting in albumin-enriched protein corona. The recruited albumin corona enabled enhanced tumor accumulation and facilitated cellular uptake, ensuring the high-efficiency delivery of nanoassemblies to tumor cells. Surprisingly, we found that the traditionally reduction-sensitive disulfide bond could also be triggered by reactive oxygen species (ROS). Such a redox dual-responsive drug release property of the disulfide bond-containing prodrug nanoassemblies further increased the selectivity in cytotoxicity between normal and tumor cells. Moreover, the disulfide bond-containing prodrug nanoassemblies exhibited the highest antitumor efficacy in vivo compared to marketed Abraxane® and other prodrug nanoassemblies. Thus, the fabrication of the maleimide-decorated disulfide bond bridged prodrug nanoassembly, integrating a tunable protein corona and on-demand drug release, is a promising strategy for improved cancer chemotherapy.

BSA-IrO2 : Catalase-like Nanoparticles with High Photothermal Conversion Efficiency and a High X-ray Absorption Coefficient for Anti-inflammation and Antitumor Theranostics

Intrinsically integrating precise diagnosis, effective therapy, and self-anti-inflammatory action into a single nanoparticle is attractive for tumor treatment and future clinical application, but still remains a great challenge. In this study, bovine serum albumin-iridium oxide nanoparticles (BSA-IrO₂ NPs) with extraordinary photothermal conversion efficiency, good photocatalytic activity, and a high X-ray absorption coefficient were prepared through one-step biomineralization. The nanoparticles allow tumor phototherapy and simultaneous photoacoustic/thermal imaging and computed tomography. More importantly, BSA-IrO₂ NPs can also act as a catalase to protect normal cells against H₂ O₂ -induced reactive oxygen pressure and inflammation while significantly enhancing photoacoustic imaging through microbubble-based inertial cavitation. These remarkable features may open up the exploration iridium-based nanomaterials in theranostics.

Large Hollow Cavity Luminous Nanoparticles with Near-Infrared Persistent Luminescence and Tunable Sizes for Tumor Afterglow Imaging and Chemo-/Photodynamic Therapies

Persistent luminous nanoparticles (PLNPs) have been capturing increasing attention in biomedical imaging because of their long-life emission and concomitant benefits ( e.g., zero-autofluorescence background, high signal-to-noise ratio). Although there are quite some synthetic methodologies to synthesize PLNPs, those for constructing functional structured PLNPs remain largely unexplored. Herein we report the design principle, synthesis route, and proof-of-concept applications of hollow structured PLNPs with near-infrared (NIR) persistent luminescence, namely afterglow, and tunable sizes for tumor afterglow imaging and chemical/photodynamic therapies. The design principle leverages on the crystallization of the immobilized parent ions on the purgeable carbon spheres. This strategy provides large and size-tunable hollow cavities to PLNPs after calcination. Building on the hollow cavity of PLNPs, high chemical drug (DOX) or photosensitizer (Si-Pc) loading can be achieved. The DOX/Si-Pc-loaded hollow PLNPs exhibit efficient tumor suppression based on the features of large cavity and afterglow of PLNPs. These hollow structured PLNPs, like traditional solid PLNPs, are quite stable and can be repeatedly activated, and particularly can selectively target tumor lesion, permitting rechargeable afterglow imaging in living mice. Our research supplies a strategy to synthesize hollow structured PLNPs, and hopefully it could inspire other innovative structures for cancer theranostics.

Nanomaterials in Neural-Stem-Cell-Mediated Regenerative Medicine: Imaging and Treatment of Neurological Diseases

Patients are increasingly being diagnosed with neuropathic diseases, but are rarely cured because of the loss of neurons in damaged tissues. This situation creates an urgent clinical need to develop alternative treatment strategies for effective repair and regeneration of injured or diseased tissues. Neural stem cells (NSCs), highly pluripotent cells with the ability of self-renewal and potential for multidirectional differentiation, provide a promising solution to meet this demand. However, some serious challenges remaining to be addressed are the regulation of implanted NSCs, tracking their fate, monitoring their interaction with and responsiveness to the tissue environment, and evaluating their treatment efficacy. Nanomaterials have been envisioned as innovative components to further empower the field of NSC-based regenerative medicine, because their unique physicochemical characteristics provide unparalleled solutions to the imaging and treatment of diseases. By building on the advantages of nanomaterials, tremendous efforts have been devoted to facilitate research into the clinical translation of NSC-based therapy. Here, recent work on emerging nanomaterials is highlighted and their performance in the imaging and treatment of neurological diseases is evaluated, comparing the strengths and weaknesses of various imaging modalities currently used. The underlying mechanisms of therapeutic efficacy are discussed, and future research directions are suggested.

Dopant-dependent crystallization and photothermal effect of Sb-doped SnO2 nanoparticles as stable theranostic nanoagents for tumor ablation

Ideal theranostic nanoagents should be "all-in-one" type nanocrystals that have a single-semiconductor component and all-required properties (such as imaging and photothermal effects), but most semiconductor nanocrystals do not have these required properties. With SnO₂ as a model of a typical wide-band semiconductor, we report the tuning from UV-responsive SnO₂ to blue SnO₂ nanocrystals with imaging ability and a Sb-doping-dependent photothermal effect. Sb-Doped SnO₂ nanocrystals were prepared by heating SbCl₃ and SnCl₄ in benzyl alcohol solution through a facile solvothermal route. When the SbCl₃/SnCl₄ molar ratio increases from 0 to 0.2/1, the obtained samples exhibit an increased photothermal effect under the irradiation of a 1064 nm laser, accompanied by gradually decreased size and crystallinity. With a further increase of the molar ratio from 0.3/1.0 to 1.0/1.0, the resulting samples demonstrate the tetragonal SnO₂ phase with amorphous-like compounds and they show no obvious enhancement of a photothermal effect. After a surface modification with biological molecules, the optimized Sb_0.2-SnO₂ nanocrystals demonstrated good stability and a high photothermal conversion efficiency of 48.3% as well as low cytotoxicity. When Sb_0.2-SnO₂ was injected into a tumor of mice, the tumor could be simultaneously detected by X-ray computed tomography (CT) and photoacoustic (PA) imaging, and then thermally ablated when exposed to a 1064 nm laser. Therefore, these nanocrystals can be used as "all-in-one" type nanoagents for imaging guided photothermal ablation of tumors under the irradiation of a laser in the second bio-transparent window.

Impact of albumin based approaches in nanomedicine: Imaging, targeting and drug delivery

A major challenge in the field of nanomedicine is to transform laboratory innovations into commercially successful clinical products. In this campaign, a variety of nanoenabled approaches have been designed and investigated for their role in biomedical applications. The advantages associated with the unique structure of albumin imparts it with the ability to interact with variety of molecules, while the functional groups present on their surface provide base for large number of modifications making it as an ideal nanocarrier system. So far, a variety of albumin based nanoenabled approaches have been intensively exploited for effective diagnosis and personalized medicine, among them some have successfully completed their journey from lab bench to marketed products. This review focuses on the recent most promising advancement in the field of albumin based nanoenabled approaches for various biomedical applications and their potential use in cancer diagnosis and therapy.

Parallel comparative studies on toxicity of quantum dots synthesized and surface engineered with different methods in vitro and in vivo

Quantum dots (QDs) have been considered to be promising probes for biosensing, bioimaging, and diagnosis. However, their toxicity issues caused by heavy metals in QDs remain to be addressed, in particular for their in vivo biomedical applications. In this study, a parallel comparative investigation in vitro and in vivo is presented to disclose the impact of synthetic methods and their following surface modifications on the toxicity of QDs. Cellular assays after exposure to QDs were conducted including cell viability assessment, DNA breakage study in a single cellular level, intracellular reactive oxygen species (ROS) receptor measurement, and transmission electron microscopy to evaluate their toxicity in vitro. Mice experiments after QD administration, including analysis of hemobiological indices, pharmacokinetics, histological examination, and body weight, were further carried out to evaluate their systematic toxicity in vivo. Results show that QDs fabricated by the thermal decomposition approach in organic phase and encapsulated by an amphiphilic polymer (denoted as QDs-1) present the least toxicity in acute damage, compared with those of QDs surface engineered by glutathione-mediated ligand exchange (denoted as QDs-2), and the ones prepared by coprecipitation approach in aqueous phase with mercaptopropionic acid capped (denoted as QDs-3). With the extension of the investigation time of mice respectively injected with QDs, we found that the damage caused by QDs to the organs can be gradually recovered. This parallel comparative investigation suggests that synthetic methods and their resulting surface microenvironment play vital roles in the acute toxicity profiles of QDs. The present study provides updated insights into the fabrication and surface engineering of QDs for their translational applications in theranostics.

Comparative Analysis of Methods for Enhancement of the Photostability of CdTe@TGA QD Colloid Solutions

The employment of colloid quantum dots in a number of applications is limited by their instability under light irradiation. Additional methods of photostability enhancement of UV+visible-irradiated TGA-stabilized CdTe quantum dots are investigated. Photostability enhancement was observed via either addition of sodium sulphite in the role of chemical oxygen absorber or addition of 1% gelatin, or, finally, by additional stabilization by bovine serum albumine (BSA). The latter method is the most promising, since it not only enhances the quantum dots' photostability but also makes them more biocompatible and extends the possibilities of their biological applications.

Vesicle formation by proton transfer driven short-tailed fatty acids of C4-C8 chain length in water

Ultrashort single-chain fatty acids self-assemble to form vesicles under certain proton-driven conditions. The protonation provides a larger charge area around the hydrophilic carbonyl headgroups, and proton shift as the key driving parameter was studied. The ultrashort fatty acids (C4-C8) formed stable unilamellar vesicles predominantly through out the whole range of tested pH levels (6.5-9.5). A proton-driven self-assembly process and effects on the phase transition were characterized by dynamic light scattering, transmission electron microscopy and cryo-transmission electron microscopy. In particular, we studied in greater detail the molecular packing characteristics of FA vesicles for geometric reasons and the protonation effect changes the molecular surface charge and further carboxylic acid headgroup motion. This study enhances the understanding of the physicochemical specificity of these membrane vesicles, and may facilitate the alteration of membrane function caused by FAs.

Site-Specific Biomimetic Precision Chemistry of Bimodal Contrast Agent with Modular Peptides for Tumor-Targeted Imaging

Various biomimetic nanoparticles have been fabricated for cancer nanotheranostics with a diverse range of proteins. However, the operating mechanisms of these reactions are still unclear, especially on the interaction between metal ions and protein, the precise binding sites, and the existence format of nanoparticles. Assuming the shortening of the amino acids sequence into several, namely short peptides, it would be much easier to investigate the biomimetic reaction mechanism. In this study, a modular peptide, possessing Au³⁺ ion coordination motifs and a Gd³⁺ ion chelation sequence, is designed and synthesized. This peptide is experimentally found effective in site-specific biomimetic synthesis of paramagnetic fluorescent gold nanoclusters (pAuNCs) with a quantum yield of 6.8%, deep red emission at 676 nm, and potent relaxivity. The gel electrophoresis result declares that the two imaging motifs in pAuNCs are quite stable. In vivo fluorescence-magnetic resonance bimodal imaging show significant tumor enhancement by pAuNCs in tumor-bearing mice. In vivo biodistribution and toxicity studies reveal that pAuNCs can be gradually cleared from the body without damage. This study presents a modular peptide that can incubate multifunctional nanoparticles in a biomimetic fashion and hopefully provides a strategy for the investigation of the mechanism of protein-mediated biomimetic synthesis.

Hyaluronic Acid Conjugated Magnetic Prussian Blue@Quantum Dot Nanoparticles for Cancer Theranostics

A multifunctional nanotheranostic agent was developed by conjugating both hyaluronic acid and bovine serum albumin coated CuInS₂-ZnS quantum dots onto the surface of magnetic Prussian blue nanoparticles. The obtained nanoagent could serve as an efficient contrast agent to simultaneously enhance near infrared (NIR) fluorescence and magnetic resonance (MR) imaging greatly. The coexistence of magnetic core and CD44 ligand hyaluronic acid was found to largely improve the specific uptake of the nanoagent by CD44 overexpressed HeLa cells upon applying an external magnetic field. Both NIR fluorescence and MR imaging in vivo proved high accumulation of the nanoagent at tumor site due to its excellent CD44 receptor/magnetic dual targeting capability. After intravenous injection of the nanoagent and treatment of external magnetic field, the tumor in nude mice was efficiently ablated upon NIR laser irradiation and the tumor growth inhibition was more than 89.95%. Such nanotheranostic agent is of crucial importance for accurately identifying the size and location of the tumor before therapy, monitoring the photothermal treatment procedure in real-time during therapy, assessing the effectiveness after therapy.

Protein/peptide-templated biomimetic synthesis of inorganic nanoparticles for biomedical applications

Currently, protein/peptide-based biomimetic mineralization has been demonstrated to be an efficient and promising strategy for synthesis of inorganic/metal nanoparticles (NPs) for bioapplications.

Albumin-Bioinspired Gd:CuS Nanotheranostic Agent for In Vivo Photoacoustic/Magnetic Resonance Imaging-Guided Tumor-Targeted Photothermal Therapy

Photothermal therapy (PTT) is attracting increasing interest and becoming more widely used for skin cancer therapy in the clinic, as a result of its noninvasiveness and low systemic adverse effects. However, there is an urgent need to develop biocompatible PTT agents, which enable accurate imaging, monitoring, and diagnosis. Herein, a biocompatible Gd-integrated CuS nanotheranostic agent (Gd:CuS@BSA) was synthesized via a facile and environmentally friendly biomimetic strategy, using bovine serum albumin (BSA) as a biotemplate at physiological temperature. The as-prepared Gd:CuS@BSA nanoparticles (NPs) with ultrasmall sizes (ca. 9 nm) exhibited high photothermal conversion efficiency and good photostability under near-infrared (NIR) laser irradiation. With doped Gd species and strong tunable NIR absorbance, Gd:CuS@BSA NPs demonstrate prominent tumor-contrasted imaging performance both on the photoacoustic and magnetic resonance imaging modalities. The subsequent Gd:CuS@BSA-mediated PTT result shows high therapy efficacy as a result of their potent NIR absorption and high photothermal conversion efficiency. The immune response triggered by Gd:CuS@BSA-mediated PTT is preliminarily explored. In addition, toxicity studies in vitro and in vivo verify that Gd:CuS@BSA NPs qualify as biocompatible agents. A biodistribution study demonstrated that the NPs can undergo hepatic clearance from the body. This study highlights the practicality and versatility of albumin-mediated biomimetic mineralization of a nanotheranostic agent and also suggests that bioinspired Gd:CuS@BSA NPs possess promising imaging guidance and effective tumor ablation properties, with high spatial resolution and deep tissue penetration.

A benchtop capillary flow layer-by-layer (CF-LbL) platform for rapid assembly and screening of biodegradable nanolayered films

Capillary flow layer-by-layer (CF-LbL) is a microfluidic platform for high throughput preparation and screening of nanolayered polymer films. Using a simple benchtop version of CF-LbL, we systematically studied the effects of various flow conditions and channel geometries on the thickness and surface roughness of the resulting films. We also investigated the biocompatibility and degradation behaviors of a series of enzymatically-degradable films made from naturally derived polymers, i.e. either alginate or hyaluronic acid as the anionic species and poly-l-arginine as the positive species. Furthermore, using one optimized film formulation for coating on the inside walls of a microfluidic chip, we successfully demonstrated the ability of this film to capture and rapidly release cancer cells from whole blood. This simple platform is expected to be a powerful tool to increase the accessibility of the LbL film assembly to a broader scientific community.

Effect of Molecular Structure on Stability of Organic Nanoparticles Formed by Bodipy Dimers

The objective was to evaluate the stability of organic nanoparticles made from Bodipy dimers. Bodipy dimers with different length of linkers were synthesized via multicomponent Passerini reaction, and could form the fluorescent nanoparticles (FNPs) through nanoprecipitation. Bodipy-dimers FNPs with long chain linker indicated better stability in biological condition than those with short one as revealed by changes of diameter and size distribution. The FNPs possessed high physical homogeneity and low cytotoxicity. The molecular structure dependent stability was also validated by confocal laser scanning microscope based on the dissociation-induced fluorescence recovering. Importantly, stable FNPs also could be used to load hydrophobic cargoes and deliver them into cytoplasm. We believe this systematic study between structure and stability might open new opportunities for designing stable nanoparticles for various applications.

Albumin-Mediated Biomineralization of Paramagnetic NIR Ag2S QDs for Tiny Tumor Bimodal Targeted Imaging in Vivo

Bimodal imaging has captured increasing interests due to its complementary characteristics of two kinds of imaging modalities. Among the various dual-modal imaging techniques, MR/fluorescence imaging has been widely studied owing to its high 3D resolution and sensitivity. There is, however, still a strong demand to construct biocompatible MR/fluorescence contrast agents with near-infrared (NIR) fluorescent emissions and high relaxivities. In this study, BSA-DTPA(Gd) derived from bovine serum albumin (BSA) as a novel kind of biotemplate is employed for biomineralization of paramagnetic NIR Ag2S quantum dots (denoted as Ag2S@BSA-DTPA(Gd) pQDs). This synthetic strategy is found to be bioinspired, environmentally benign, and straightforward. The obtained Ag2S@BSA-DTPA(Gd) pQDs have fine sizes (ca. 6 nm) and good colloidal stability. They exhibit unabated NIR fluorescent emission (ca. 790 nm) as well as high longitudinal relaxivity (r1 = 12.6 mM(-1) s(-1)) compared to that of commercial Magnevist (r1 = 3.13 mM(-1) s(-1)). In vivo tumor-bearing MR and fluorescence imaging both demonstrate that Ag2S@BSA-DTPA(Gd) pQDs have pronounced tiny tumor targeting capability. In vitro and in vivo toxicity study show Ag2S@BSA-DTPA(Gd) pQDs are biocompatible. Also, biodistribution analysis indicates they can be cleared from body mainly via liver metabolism. This protein-mediated biomineralized Ag2S@BSA-DTPA(Gd) pQDs presents great potential as a novel bimodal imaging contrast agent for tiny tumor diagnosis.

Synthesis and Cell Imaging of a Near-Infrared Fluorescent Magnetic "CdHgTe-Dextran-Magnetic Layered Double Hydroxide-Fluorouracil" Composite

In this article, a water-soluble near-infrared quantum dots of CdHgTe were prepared and subsequently combined with the drug delivery system "dextran-magnetic layered double hydroxide-fluorouracil" (DMF) to build a new nanostructure platform in form of CdHgTe@DMF, in which the fluorescent probe function of quantum dots and the magnetic targeting transport and slow-release curative effect of DMF were blended availably together. The luminescent property particle size, and internal structure of the composite were characterized using fluorescence spectrophotometer, ultraviolet spectrophotometer, laser particle size distribution, TEM, X-ray diffraction, and Fourier transform infrared. The experimental study on fluorescent tags effect and magnetic targeting performance of the multifunctional platform were performed by fluorescent confocal imaging. The results showed that the CdHgTe could be grafted successfully onto the surface of DMF by electrostatic coupling. The CdHgTe@DMF composite showed super-paramagnetic and photoluminescence property in the near-infrared wavelength range of 575-780 nm. Compared with CdHgTe, the CdHgTe@DMF composite could significantly improve the cell imaging effect, the label intensity increased with the magnetic field intensity, and obeyed the linear relationship Dmean = 1.758 + 0.0075M under the conditions of magnetic field interference. It can be implied that the CdHgTe@DMF may be an effective multifunction tool applying to optical bioimaging and magnetic targeted therapy.

Improving the MR Imaging Sensitivity of Upconversion Nanoparticles by an Internal and External Incorporation of the Gd(3+) Strategy for in Vivo Tumor-Targeted Imaging

Gd(3+)-ion-doped upconversion nanoparticles (UCNPs), integrating the advantages of upconversion luminescence and magnetic resonance imaging (MRI) modalities, are capturing increasing attention because they are promising to improve the accuracy of diagnosis. The embedded Gd(3+) ions in UCNPs, however, have an indistinct MRI enhancement owing to the inefficient exchange of magnetic fields with the surrounding water protons. In this study, a novel approach is developed to improve the MR imaging sensitivity of Gd(3+)-ion-doped UCNPs. Bovine serum albumin (BSA) bundled with DTPA-Gd(3+) (DTPA(Gd)) is synthesized both as the MR imaging sensitivity synergist and phase-transfer ligand for the surface engineering of UCNPs. The external Gd(3+) ion attachment strategy is found to significant improve the MR imaging sensitivity of Gd(3+)-ion-doped UCNPs. The relaxivity analysis shows that UCNPs@BSA·DTPA(Gd) exhibit higher relaxivity values than do UCNPs@BSA without DTPA(Gd) moieties. Another relaxivity study discloses a striking message that the relaxivity value does not always reflect the realistic MRI enhancement capability. The high concentration of Gd(3+)-ion-containing UCNPs with further surface-engineered BSA·DTPA(Gd) (denoted as UCNPs-H@BSA·DTPA(Gd)) exhibits a more pronounced MRI enhancement capability compared to the other two counterparts [UCNPs-N@BSA·DTPA(Gd) and UCNPs-L@BSA·DTPA(Gd) (-N and -L are denoted as zero and low concentrations of Gd(3+) ion doping, respectively)], even though it holds the lowest r1 of 1.56 s(-1) per mmol L(-1) of Gd(3+). The physicochemical properties of UCNPs are essentially maintained after BSA·DTPA(Gd) surface decoration with good colloidal stability, in addition to improving the MR imaging sensitivity. In vivo T1-weighted MRI shows potent tumor-enhanced MRI with UCNPs-H@BSA·DTPA(Gd). An in vivo biodistribution study indicates that it is gradually excreted from the body via hepatobiliary and renal processing with no obvious toxicity. It could therefore be concluded, with improved MR imaging sensitivity by an internal and external incorporation of Gd(3+) strategy, that UCNPs-H@BSA·DTPA(Gd) presents great potential as an alternative in tumor-targeted MR imaging.

Hydrophobin-Encapsulated Quantum Dots

The phase transfer of quantum dots to water is an important aspect of preparing nanomaterials that are suitable for biological applications, and although numerous reports describe ligand exchange, very few describe efficient ligand encapsulation techniques. In this report, we not only report a new method of phase transferring quantum dots (QDs) using an amphiphilic protein (hydrophobin) but also describe the advantages of using a biological molecule with available functional groups and their use in imaging cancer cells in vivo and other imaging applications.

Hydrophilic Magnetofluorescent Nanobowls: Rapid Magnetic Response and Efficient Photoluminescence

Multifunctional integration based on a single nanostructure is emerging as a promising paradigm to future functional materials. In this paper, novel magnetofluorescence nanobowls built with ferroferric mandrel and quantum dots exoderm is reported. Magnetic mandrels are stacked into nanobowls though hydrophobic primary Fe3O4 nanocrystals dragged into anion polyelectrolyte aqueous solution via forced solvent evaporation. Bright luminescence core/shell/shell CdSe/CdS/ZnS quantum dots (QDs) are modified with cationic hyperbranched polyethylenimine (PEI). Through electrostatic interactions, positively charged PEI-coated QDs are anchored on the surface of magnetic mandrel. Under this method, the luminescence of QDs is not quenched by magnetic partners in the resultant magnetoflurescence nanobowls. Such magnetoflurescence nanobowls exhibit high saturation magnetization, superparamagnetic characteristics at room temperature, superior water dispersibility, and excellent photoluminescence properties. The newly developed magnetoflurescence nanobowls open a new dimension in efforts toward multimodal imaging probes combining strong magnetization and efficient fluorescence in tandem for biosensors and clinical diagnostic imaging.

Influence of Protein Surface Coverage on Anomalously Strong Adsorption Sites

Serum albumin is commonly used as a blocking agent to reduce nonspecific protein adsorption in bioassays and biodevices; however, the details of this process remain poorly understood. Using single molecule techniques, we investigated the dynamics of human serum albumin (HSA) on four model surfaces as a function of protein concentration. By constructing super-resolution maps, identifying anomalously strong adsorption sites, and quantifying surface heterogeneity, we found that the concentration required for site blocking varied dramatically with surface chemistry. When expressed in terms of protein surface coverage, however, a more consistent picture emerged, where a significant fraction of strong sites were passivated at a fractional coverage of 10(-4). On fused silica (FS), "non-fouling" oligo (ethylene glycol) functionalized FS, and hydrophobically modified FS, a modest additional site blocking effect continued at higher coverage. However, on amine-functionalized surfaces, the surface heterogeneity exhibited a minimum at a coverage of ∼10(-4). Using intermolecular Förster resonance energy transfer (FRET), we determined that new anomalous strong sites were created at higher coverage on amine surfaces and that adsorption to these sites was associated with protein-protein interactions, i.e., surface-induced aggregation.