Nanoparticle Assembly of Surface-Modified Proteins

Organic Donor-Acceptor-Donor Trimers Nanoparticles Stabilized by Amphiphilic Block Copolymers for Photocatalytic Generation of H2

Photocatalytic generation of H2 via water splitting emerges as a promising avenue for the next generation of green hydrogen due to its low carbon footprint. Herein, a versatile platform is designed to the preparation of functional π-conjugated organic nanoparticles dispersed in aqueous phase via mini-emulsification. Such particles are composed of donor-acceptor-donor (DAD) trimers prepared via Stille coupling, stabilized by amphiphilic block copolymers synthesized by reversible addition-fragmentation chain transfer polymerization. The hydrophilic segment of the block copolymers will not only provide colloidal stability, but also allow for precise control over the surface functionalization. Photocatalytic tests of the resulting particles for H2 production resulted in promising photocatalytic activity (≈0.6 mmol g-1 h-1). This activity is much enhanced compared to that of DAD trimers dispersed in the water phase without stabilization by the block copolymers.

Protein-based Nanoparticles: From Drug Delivery to Imaging, Nanocatalysis and Protein Therapy

Proteins and enzymes are versatile biomaterials for a wide range of medical applications due to their high specificity for receptors and substrates, high degradability, low toxicity, and overall good biocompatibility. Protein nanoparticles are formed by the arrangement of several native or modified proteins into nanometer-sized assemblies. In this review, we will focus on artificial nanoparticle systems, where proteins are the main structural element and not just an encapsulated payload. While under natural conditions, only certain proteins form defined aggregates and nanoparticles, chemical modifications or a change in the physical environment can further extend the pool of available building blocks. This allows the assembly of many globular proteins and even enzymes. These advances in preparation methods led to the emergence of new generations of nanosystems that extend beyond transport vehicles to diverse applications, from multifunctional drug delivery to imaging, nanocatalysis and protein therapy.

Strategies for Improving Selectivity and Sensitivity of Schiff Base Fluorescent Chemosensors for Toxic and Heavy Metals

Toxic cations, including heavy metals, pose significant environmental and health risks, necessitating the development of reliable detection methods. This review investigates the techniques and approaches used to strengthen the sensitivity and selectivity of Schiff base fluorescent chemosensors designed specifically to detect toxic and heavy metal cations. The paper explores a range of strategies, including functional group variations, structural modifications, and the integration of nanomaterials or auxiliary receptors, to amplify the efficiency of these chemosensors. By improving selectivity towards targeted cations and achieving heightened sensitivity and detection limits, consequently, these strategies contribute to the advancement of accurate and efficient detection methods while increasing the range of end-use applications. The findings discussed in this review offer valuable insights into the potential of leveraging Schiff base fluorescent chemosensors for the accurate and reliable detection and monitoring of heavy metal cations in various fields, including environmental monitoring, biomedical research, and industrial safety.

Biopharmaceutical nanoclusters: Towards the self-delivery of protein and peptide therapeutics

Protein and peptide biopharmaceuticals have had a major impact on the treatment of a number of diseases. There is a growing interest in overcoming some of the challenges associated with biopharmaceuticals, such as rapid degradation in physiological fluid, using nanocarrier delivery systems. Biopharmaceutical nanoclusters (BNCs) where the therapeutic protein or peptide is clustered together to form the main constituent of the nanocarrier system have the potential to mimic the benefits of more established nanocarriers (e.g., liposomal and polymeric systems) whilst eliminating the issue of low drug loading and potential side effects from additives. These benefits would include enhanced stability, improved absorption, and increased biopharmaceutical activity. However, the successful development of BNCs is challenged by the physicochemical complexity of the protein and peptide constituents as well as the dynamics of clustering. Here, we present and discuss common methodologies for the synthesis of therapeutic protein and peptide nanoclusters, as well as review the current status of this emerging field.

The Core-Shell Structure, Not Sugar, Drives the Thermal Stabilization of Single-Enzyme Nanoparticles

Trehalose is widely assumed to be the most effective sugar for protein stabilization, but exactly how unique the structure is and the mechanism by which it works are still debated. Herein, we use a polyion complex micelle approach to control the position of trehalose relative to the surface of glucose oxidase within cross-linked and non-cross-linked single-enzyme nanoparticles (SENs). The distribution and density of trehalose molecules in the shell can be tuned by changing the structure of the underlying polymer, poly(N-[3-(dimethylamino)propyl] acrylamide (PDMAPA). SENs in which the trehalose is replaced with sucrose and acrylamide are prepared as well for comparison. Isothermal titration calorimetry, dynamic light scattering, and asymmetric flow field-flow fraction in combination with multiangle light scattering reveal that two to six polymers bind to the enzyme. Binding either trehalose or sucrose close to the enzyme surface has very little effect on the thermal stability of the enzyme. By contrast, encapsulation of the enzyme within a cross-linked polymer shell significantly enhances its thermal stability and increases the unfolding temperature from 70.3 °C to 84.8 °C. Further improvements (up to 92.8 °C) can be seen when trehalose is built into this shell. Our data indicate that the structural confinement of the enzyme is a far more important driver in its thermal stability than the location of any sugar.

Kinetics of Network Formation and Heterogeneous Dynamics of an Egg White Gel Revealed by Coherent X-Ray Scattering

The kinetics of heat-induced gelation and the microscopic dynamics of a hen egg white gel are probed using x-ray photon correlation spectroscopy along with ultrasmall-angle x-ray scattering. The kinetics of structural growth reveals a reaction-limited aggregation process with a gel fractal dimension of ≈2 and an average network mesh size of ca. 400 nm. The dynamics probed at these length scales reveals an exponential growth of the characteristic relaxation times followed by an intriguing steady state in combination with a compressed exponential correlation function and a temporal heterogeneity. The degree of heterogeneity increases with decreasing length scale. We discuss our results in the broader context of experiments and models describing attractive colloidal gels.

Self-Assembling Proteins for Design of Anticancer Nanodrugs

Inspired by the diverse protein-based structures and materials in organisms, proteins have been expected as promising biological components for constructing nanomaterials toward various applications. In numerous studies protein-based nanomaterials have been constructed with the merits of abundant bioactivity and good biocompatibility. However, self-assembly of proteins as a dominant approach in constructing anticancer nanodrugs has not been reviewed. Here, we provide a comprehensive account of the role of protein self-assembly in fabrication, regulation, and application of anticancer nanodrugs. The supramolecular strategies, building blocks, and molecular interactions of protein self-assembly as well as the properties, functions, and applications of the resulting nanodrugs are discussed. The applications in chemotherapy, radiotherapy, photodynamic therapy, photothermal therapy, gene therapy, and combination therapy are included. Especially, manipulation of molecular interactions for realizing cancer-specific response and cancer theranostics are emphasized. By expounding the impact of molecular interactions on therapeutic activity, rational design of highly efficient protein-based nanodrugs for precision anticancer therapy can be envisioned. Also, the challenges and perspectives in constructing nanodrugs based on protein self-assembly are presented to advance clinical translation of protein-based nanodrugs and next-generation nanomedicine.

pH-Responsive protein nanoparticlesviaconjugation of degradable PEG to the surface of cytochromec

A protein nanoparticle system based on cytochromecwas modified with acid-degradable polyethylene glycol (PEGylation). Vinyl ether moieties distributed in the polyether backbone, enabled particle degradation at slightly acidic pH.

AB loop engineered ferritin nanocages for drug loading under benign experimental conditions

Human ferritin has been explored as a potential drug nanocarrier, but extreme conditions (pH ≤ 2.0) are required for the encapsulation of drugs. Here, by engineering the AB loop of ferritin, we obtained a new ferritin variant with no new pores, which can disassemble at pH 3.0 or 4.0 and reassemble at pH 7.0. Consequently, under mild conditions, drugs can be encapsulated within this new ferritin nanocage.

Facile and Controllable Fabrication of Protein-Only Nanoparticles through Photo-Induced Crosslinking of Albumin and Their Application as DOX Carriers

Protein-based nanoparticles, as an alternative to conventional polymer-based nanoparticles, offer great advantages in biomedical applications owing to their functional and biocompatible characteristics. However, the route of fabrication towards protein-based nanoparticles faces substantial challenges, including limitations in size control and unavoidable usage of toxic crosslinkers or organic solvents, which may raise safety concerns related to products and their degradation components. In the present study, a photo-induced crosslinking approach was developed to prepare stable, size-controlled protein-only nanoparticles. The facile one-step reaction irradiated by visible light enables the formation of monodispersed bovine serum albumin nanoparticles (BSA NPs) within several minutes through a tyrosine photo-redox reaction, requiring no cross-linking agents. The size of the BSA NPs could be precisely manipulated (from 20 to 100 nm) by controlling the duration time of illumination. The resultant BSA NPs exhibited spherical morphology, and the α-helix structure in BSA was preserved. Further study demonstrated that the 35 nm doxorubicin (DOX)-loaded BSA NPs achieved a drug loading content of 6.3%, encapsulation efficiency of 70.7%, and a controlled release profile with responsivity to both pH and reducing conditions. Importantly, the in vitro drug delivery experiment demonstrated efficient cellular internalizations of the DOX-loaded BSA NPs and inhibitory activities on MCF-7 and HeLa cells. This method shows the promise of being a platform for the green synthesis of protein-only nanoparticles for biomedical applications.

All Wrapped up: Stabilization of Enzymes within Single Enzyme Nanoparticles

Enzymes are extremely useful in many industrial and pharmaceutical areas due to their ability to catalyze reactions with high selectivity. In order to extend their lifetime, significant efforts have been made to increase their stability using protein- or medium engineering as well as by chemical modification. Many researchers have explored the immobilization of enzymes onto carriers, or entrapment within a matrix, framework or nanoparticle with the hope of constricting the movement of the enzyme and shielding it from aggressive environments, thus delaying the denaturation. These strategies often balance three competing interests: (i) maintaining high enzymatic activity, (ii) ensuring good long-term stability against temperature, dehydration, organic solvents, and or aggressive pH, and (iii) enabling a tuning or reversible switching of enzyme activity. In most cases, multiple enzymes will be contained within a single nanoparticle or matrix, but in recent years researchers have begun to wrap up individual enzymes within single enzyme nanoparticles (SENs). In these nanoparticles the enzyme is stabilized by a thin shell, typically a polymer, prepared either by in situ polymerization from the enzyme surface or by assembling a preformed polymer around it. Because of the increased control over the environment directly around the enzyme, and the possibility of more directly controlling substrate diffusion, many SENs show remarkable stability while retaining high initial activities even for quite fragile enzymes. Moreover, the activity of the enzyme can often be more easily fine-tuned by adjusting the layer properties. We postulate that this emerging field will offer exciting and elegant opportunities to both extend the catalytic lifetime of enzymes in aggressive solvents, temperatures and pH, and enable their activity to be switched on and off on demand by modulation of the outer material layer.

Synthesis of gold nanocluster-loaded lysozyme nanoparticles for label-free ratiometric fluorescent pH sensing: applications to enzyme–substrate systems and cellular imaging

We have demonstrated the synthesis of gold nanocluster-loaded lysozyme nanoparticles as a dual-emission probe for ratiometric sensing of pH changes in enzyme–substrate systems and live cells.

Synergistic combination chemotherapy using carrier-free celastrol and doxorubicin nanocrystals for overcoming drug resistance

A key challenge of chemotherapy in clinical treatments is multidrug resistance (MDR), which mainly arises from drug efflux-induced tumor cell survival. Thus, it is necessary to provide biocompatible chemotherapeutics to improve drug accumulation in MDR cells. Herein, two clinical small molecular drugs, celastrol (CST) and doxorubicin (DOX), were self-assembled into carrier-free and biocompatible nanoparticles (CST/DOX NPs) via a simple and green precipitation method for synergistic combination chemotherapy to overcome DOX resistance. These spherical CST/DOX NPs can improve the water-solubility of CST, reduce the dosage of DOX, and therefore significantly enhance cellular drug accumulation by activating heat shock factor 1 (HSF-1) and inhibiting NF-κB to depress P-gp expression, which results in apoptosis and autophagy of DOX resistant cells through the ROS/JNK signaling pathway. Finally, synergistic combination chemotherapy was attained in both MCF-7/MDR cells and 3D multicellular tumor spheroids. Thus, CST/DOX NPs provide an alternative for overcoming drug resistance in future clinical applications.

Self-Templated, Green-Synthetic, Size-Controlled Protein Nanoassembly as a Robust Nanoplatform for Biomedical Application

Despite inherent advantages over their synthetic polymer-based counterparts, protein nanoparticles remain unsatisfactory in fabrication owing to their low size control, usage of toxic cross-linkers, or organic solvents. This partially contributes to the marginal benefits of Abraxane in clinics. Herein, a green-synthetic, size-controlled approach was developed to generate stable albumin nanoparticles. Physically packed ovalbumin nanoclusters were temporally formed in heat, which was then used as the template to form protein nanoparticles chemically stabilized by the intermolecular disulfide network. Exposure of embedded free thiols within a hydrophobic albumin structure and oxidation of them into disulfides (2-3 fold reduction of thiols groups in this process) were identified as key factors during the process. The fact that the structure was stable in sodium dodecyl sulfate treatment (hydrophobic destroyer) while disassembling fast in reduction condition (to cleave disulfide) validated the disulfide cross-linked mechanism. The developed approach is facile and reproducible with precision size control (from tens to hundreds of nanometers). The approach can be extended to other proteins such as bovine serum albumin, underscoring the potential universal applicability. Further study demonstrated that the resultant protein nanoparticles can be a robust nanoplatform for extensive biomedical applications including drug delivery (doxorubicin encapsulation of 5.7%), target bioconjugation, or robust immune adjuvant effect.

Biosynthesis of Au, Ag and Au-Ag bimetallic nanoparticles using protein extracts of Deinococcus radiodurans and evaluation of their cytotoxicity

Background

Biosynthesis of noble metallic nanoparticles (NPs) has attracted significant interest due to their environmental friendly and biocompatible properties.

Methods

In this study, we investigated syntheses of Au, Ag and Au–Ag bimetallic NPs using protein extracts of Deinococcus radiodurans, which demonstrated powerful metal-reducing ability. The obtained NPs were characterized and analyzed by various spectroscopy techniques.

Results

The D. radiodurans protein extract-mediated silver nanoparticles (Drp-AgNPs) were preferably monodispersed and stably distributed compared to D. radiodurans protein extract-mediated gold nanoparticles (Drp-AuNPs). Drp-AgNPs and Drp-AuNPs exhibited spherical morphology with average sizes of 37.13±5.97 nm and 51.72±7.38 nm and zeta potential values of −18.31±1.39 mV and −15.17±1.24 mV at pH 7, respectively. The release efficiencies of Drp-AuNPs and Drp-AgNPs measured at 24 h were 3.99% and 18.20%, respectively. During the synthesis process, Au(III) was reduced to Au(I) and further to Au(0) and Ag(I) was reduced to Ag(0) by interactions with the hydroxyl, amine, carboxyl, phospho or sulfhydryl groups of proteins and subsequently stabilized by these groups. Some characteristics of Drp-AuNPs were different from those of Drp-AgNPs, which could be attributed to the interaction of the NPs with different binding groups of proteins. The Drp-AgNPs could be further formed into Au–Ag bimetallic NPs via galvanic replacement reaction. Drp-AuNPs and Au–Ag bimetallic NPs showed low cytotoxicity against MCF-10A cells due to the lower level of intracellular reactive oxygen species (ROS) generation than that of Drp-AgNPs.

Conclusions

These results are crucial to understand the biosynthetic mechanism and properties of noble metallic NPs using the protein extracts of bacteria. The biocompatible Au or Au–Ag bimetallic NPs are applicable in biosensing, bioimaging and biomedicine.

Preoccupation of Empty Carriers Decreases Endo-/Lysosome Escape and Reduces the Protein Delivery Efficiency of Mesoporous Silica Nanoparticles

Endo-/lysosome escape is a major challenge in nanoparticle-based protein delivery for cancer therapy. To enhance the endo-/lysosomal escape and increase the efficacy of protein delivery, current strategies mainly focus on destroying endo-/lysosomes by employing modified nanoparticles, such as pH-sensitive polyplexes, cell-penetrating peptides, and photosensitive molecules. Herein, we hypothesize that pretreatment with empty nanocarriers might make endo-/lysosomes occupied and affect the endo/lysosomal escape of protein subsequently delivery by nanocarriers. We first treated breast carcinoma MDA-MB-231 cells with a high concentration of empty nanocarriers, mesoporous silica nanoparticles (MSN), to occupy the endo-/lysosome. After 2 h, we treated the cells with a lower concentration of fluorescein isothiocyanate-labeled MSN (MSN-FITC) and investigated the intracellular spatial and temporal distribution of MSN-FITC and their colocalization with endo-/lysosomes. We discovered the preoccupation of endo-/lysosomes by the empty nanocarriers did exist, mainly through changing the spatial distribution of the subsequently introduced nanocarriers. Furthermore, for the protein delivery, we observed reduced MSN-saporin delivery after endo-/lysosome preoccupation by MSN empty carriers. A similar result is observed for the delivery of cytochrome C by MSN but not for the small-molecule anticancer drug doxorubicin. The results show that the empty nanocarriers inhibit the endo-/lysosome intracellular trafficking process and decrease the endo-/lysosome escape of proteins subsequently delivered by the nanocarriers. This new discovered phenomenon of declined endo-/lysosome escape after endo-/lysosome preoccupation indicates that repeated treatment by nanomaterials with low protein-loading capacity may not yield a good cancer therapeutic effect. Therefore, it provides a new insightful perspective on the role of nanomaterial carriers in intracellular protein delivery.

Silk Nanofibers as Robust and Versatile Emulsifiers

Peptides have been extensively studied as emulsifiers due to their sequence and size control, biocompatibility, versatility, and stabilizing capacity. However, cost and mass production remain the challenges for broader utility for these emulsifiers. Here we demonstrate the utility of silk fibroin nanofibers as emulsifiers, with superior functions to the more traditional peptide emulsifiers. This silk nanofiber system is universal for different oil phases with various polarities and demonstrates control of microcapsule size through tuning the ratio of silk fibroin nanofiber solutions to oils. Besides the improved stabilizing capacity to peptides, these silk fibroin nanofibers endow additional stability to the emulsions formed under high salt concentration and low pH. Highly efficient encapsulation of biomarkers through interfacial networks suggests potential applications in therapeutics, food, and cosmetics. Compared to peptide emulsifiers, these silk fibroin nanofibers offer advantages in terms of cost, purification, and production scale, without compromising biocompatibility, stabilizing capacity, and versatility.

Efficient Way to Generate Protein-Based Nanoparticles by in-Situ Photoinitiated Polymerization-Induced Self-Assembly

Protein-based nanoparticles with tailored properties by using different functional proteins as building blocks have many actual and potential applications in biomedicine, biotechnology, and nanotechnology. In this study, we demonstrated a facile and efficient way to synthesize protein-based nanoparticles by taking advantage of photoinitiated reversible addition-fragmentation chain transfer (RAFT) polymerization-induced self-assembly by using multi-RAFT modified bovine serum albumin (BSA) as a macro-RAFT agent. The growth of the PHPMA chains results in the increase of the hydrophobicity of the star BSA-PHPMA conjugates, and when reaching the critical aggregation concentration in aqueous solution, they will aggregate into nanoparticles via the hydrophobic interaction of PHPMA. The generated nanoparticles also showed excellent encapsulation ability toward both hydrophobic and hydrophilic components, and as a proof of concept, after loading cancer drug DOX or biomacromolecule DNA, the protease-mediated release of the encapsulants was demonstrated. It is anticipated that the described method may open up new opportunities for designing a variety of protein-polymer self-assembled nanostructures tailored to specific applications.

Methods of protein surface PEGylation under structure preservation for the emulsion-based formation of stable nanoparticles

We evaluated different methods for a high surface PEGylation of lysozyme. The resulting lipophilic enzymes can be used for the formation of stable nanoparticles.