Protein-assisted one-pot synthesis and biofunctionalization of spherical gold nanoparticles for selective targeting of cancer cells

Saporin Toxin Delivered by Engineered Colloidal Nanoparticles Is Strongly Effective against Cancer Cells

Ribosome-inactivating proteins, including Saporin toxin, have found application in the search for innovative alternative cancer therapies to conventional chemo- and radiotherapy. Saporin’s main mechanism of action involves the inhibition of cytoplasmic protein synthesis. Its strong theoretical efficacy is counterbalanced by negligible cell uptake and diffusion into the cytosol. In this work, we demonstrate that by immobilizing Saporin on iron oxide nanoparticles coated with an amphiphilic polymer, which promotes nanoconjugate endosomal escape, a strong cytotoxic effect mediated by ribosomal functional inactivation can be achieved. Cancer cell death was mediated by apoptosis dependent on nanoparticle concentration but independent of surface ligand density. The cytotoxic activity of Saporin-conjugated colloidal nanoparticles proved to be selective against three different cancer cell lines in comparison with healthy fibroblasts.

Preparation, Functionalization, Modification, and Applications of Nanostructured Gold: A Critical Review

Gold nanoparticles (Au NPs) play a significant role in science and technology because of their unique size, shape, properties and broad range of potential applications. This review focuses on the various approaches employed for the synthesis, modification and functionalization of nanostructured Au. The potential catalytic applications and their enhancement upon modification of Au nanostructures have also been discussed in detail. The present analysis also offers brief summaries of the major Au nanomaterials synthetic procedures, such as hydrothermal, solvothermal, sol-gel, direct oxidation, chemical vapor deposition, sonochemical deposition, electrochemical deposition, microwave and laser pyrolysis. Among the various strategies used for improving the catalytic performance of nanostructured Au, the modification and functionalization of nanostructured Au produced better results. Therefore, various synthesis, modification and functionalization methods employed for better catalytic outcomes of nanostructured Au have been summarized in this review.

Does conjugation strategy matter? Cetuximab-conjugated gold nanocages for targeting triple-negative breast cancer cells

The efficient targeting of cancer cells depends on the success of obtaining the active targeting of overexpressed receptors. A very accurate design of nanoconjugates should be done via the selection of the conjugation strategy to achieve effective targeted nanoconjugates. Here, we present a detailed study of cetuximab-conjugated nonspherical gold nanocages for the active targeting of triple-negative breast cancer cells, including MDA-MB-231 and MDA-MB-468. A few different general strategies were selected for monoclonal antibody conjugation to the nanoparticle surface. By varying the bioconjugation conditions, including antibody orientation or the presence of a polymeric spacer or recombinant protein biolinker, we demonstrate the importance of a rational design of nanoconjugates. A quantitative study of gold content via ICP-AES allowed us to compare the effectiveness of cellular uptake as a function of the conjugation strategy and confirmed the active nature of nanoparticle internalization in cancer cells via epidermal growth factor receptor recognition, corroborating the importance of the rational design of nanomaterials for nanomedicine.

Surface-enhanced Raman spectroscopy (SERS) nanoprobes for ratiometric detection of cancer cells

A surface-enhanced Raman spectroscopic strategy is developed for ratiometric detection of cancer cells by quantifying the expression ratio of extracellular biomarkers.

Sensor array for qualitative and quantitative analysis of metal ions and metal oxyanion based on colorimetric and chemometric methods

Gold nanoparticle (AuNP)-based colorimetric sensor is sensitive for the detection of metal ions and metal oxyanion in aqueous solution. However, this method is usually not suitable for multi-objective analysis in complex mixture systems because it is suffering from interference of co-existents. In the present paper, we proposed a sensitive, flexible, low-cost, and multi-units sensor method for the qualitative and quantitative analysis of metal ions and metal oxyanion based on the global ultraviolet and visible (UV-Vis) spectra of amino acid-gold nanoparticles (amino acid-AuNPs) sensors in the range of 230-800 nm. Different amino acids (L-Histidine, L-Lysine, L-Methionine, D-Penicillium) which can prevent the aggregation of the AuNPs in NaCl solution, were investigated to build sensor arrays responding to different ions induced AuNPs aggregation. The UV-Vis spectra that Cd²⁺, Ba²⁺, Mn²⁺, Ni²⁺, Cu²⁺, Fe³⁺, Cr³⁺, Cr₂O₇^2-, Sn⁴⁺, Pb²⁺ induce amino acid-AuNPs displayed different characteristics and the ions were classified correctly by using partial least squares-discriminant analysis (PLS-DA). Taking the advantage of the multivariate analysis and sensor arrays, we simultaneously quantified the ions in binary and ternary mixture systems (Cr³⁺/Cr₂O₇^2-, Fe³⁺/Cd²⁺, Fe³⁺/Cr³⁺/Cr₂O₇^2-). Data fusion methods further improved the prediction accuracy of the chemometric models built on multi-amino acids-AuNPs sensors. The proposed method has a potential for analyzing metal ions and metal oxyanion in much more complex mixture systems.

Surface Modification of Gold Nanoparticles with Small Molecules for Biochemical Analysis

As one of the major tools for and by chemical science, biochemical analysis is becoming increasingly important in fields like clinical diagnosis, food safety, environmental monitoring, and the development of chemistry and biochemistry. The advancement of nanotechnology boosts the development of analytical chemistry, particularly the nanoparticle (NP)-based approaches for biochemical assays. Functional NPs can greatly improve the performance of biochemical analysis because they can accelerate signal transduction, enhance the signal intensity, and enable convenient signal readout due to their unique physical and chemical properties. Surface chemistry is a widely used tool to functionalize NPs, and the strategy for surface modification is of great significance to the application of NP-mediated biochemical assays. Surface chemistry not only affects the quality of NPs (stability, monodispersity, and biocompatibility) but also provides functional groups (-COO^-, -NH₃⁺, -CHO, and so on) or charges that can be exploited for bioconjugation or ligand exchange. Surface chemistry also dictates the sensitivity and specificity of the NP-mediated biochemical assays, since it is vital to the orientation, accessibility, and bioactivity of the functionalized ligands on the NPs. In this Account, we will focus on surface chemistry for functionalization of gold nanoparticles (AuNPs) with small organic molecules for biochemical analysis. Compared to other NPs, AuNPs have many merits including controllable synthesis, easy surface modification and high molar absorption coefficient, making them ideal probes for biochemical assays. Small-molecule functionalized AuNPs are widely employed to develop sensors for biochemical analysis, considering that small molecules, such as amino acids and sulfhydryl compounds, are more easily and controllably bioconjugated to the surface of AuNPs than biomacromolecules due to their less complex structure and steric hindrance. The orientation and accessibility of small molecules on AuNPs in most cases can be precisely controlled without compromising their bioactivity as well, thus ensuring the performance, such as the specificity and sensitivity, of AuNP-based biochemical assays. This Account reviews recent progress in the surface chemistry of functionalized AuNPs for biochemical assays. The surface chemistries mainly include click chemistry, ligand exchange reaction, and coordination-based recognition. These surface-modified AuNPs allow for assaying a range of important biochemical markers including metal ions, small biomolecules, enzymes, and antigens and antibodies. Applications of these systems range from environmental monitoring to medical diagnostics. This Account highlights the advantages and limitations (sensitivity, detection efficiency, and stability) that AuNP-mediated assays still have compared with conventional analytical methods. This Account also discusses the future research directions of surface-modified AuNP-mediated biochemical analysis. The main aim of this Account is to summarize the current surface modification strategies for AuNPs and further demonstrate how to make use of surface modification strategies to effectively improve the performance of AuNP-mediated analytical methods for a wide variety of applications relating to biochemical analysis.

Biocatalytic Formation of Gold Nanoparticles Decorated with Functional Proteins inside Recombinant Escherichia coli Cells

A novel strategy for the preparation of protein-decorated gold nanoparticles (Au NPs) was developed inside Escherichia coli cells, where an artificial oxidoreductase, composed of antibody-binding protein (pG), Bacillus stearothermophilus glycerol dehydrogenase (BsGLD) and a peptide tag with gold-binding affinity (H6C), was overexpressed in the cytoplasm. In situ formation of Au NPs was promoted by a natural electron-donating cofactor, nicotinamide adenine dinucleotide (NAD), which was regenerated to the reduced form of NADH by the catalytic activity of the fusion protein (pG-BsGLD-H6C) overexpressed in the cytoplasm of E. coli, with the concomitant addition of exogenous glycerol to the reaction system. The fusion protein was self-immobilized on Au NPs inside the E. coli cells, which was confirmed by SDS-PAGE and western blotting analyses of the resultant Au NPs. Finally, the IgG binding ability of the pG moiety displayed on Au NPs was evaluated by an enzyme-linked immunosorbent assay.

Biosynthesis of Metal Nanoparticles: Novel Efficient Heterogeneous Nanocatalysts

This review compiles the most recent advances described in literature on the preparation of noble metal nanoparticles induced by biological entities. The use of different free or substituted carbohydrates, peptides, proteins, microorganisms or plants have been successfully applied as a new green concept in the development of innovative strategies to prepare these nanoparticles as different nanostructures with different forms and sizes. As a second part of this review, the application of their synthetic ability as new heterogonous catalysts has been described in C-C bond-forming reactions (as Suzuki, Heck, cycloaddition or multicomponent), oxidations and dynamic kinetic resolutions.

Size-Controlled Formation of Noble-Metal Nanoparticles in Aqueous Solution with a Thiol-Free Tripeptide

A combinatorial screening revealed the peptide H-His-d-Leu-d-Asp-NH2 (1) as an additive for the generation of monodisperse, water-soluble palladium nanoparticles with average diameters of 3 nm and stabilities of over 9 months. The tripeptide proved to be also applicable for the size-controlled formation of other noble-metal nanoparticles (Pt and Au). Studies with close analogues of peptide 1 revealed a specific role of each of the three amino acids for the formation and stabilization of the nanoparticles. These data combined with microscopic and spectroscopic analyses provided insight into the structure of the self-assembled peptidic monolayer around the metal core. The results open interesting prospects for the development of functionalized metal nanoparticles.

An enhanced ascorbate peroxidase 2/antibody-binding domain fusion protein (APEX2-ABD) as a recombinant target-specific signal amplifier

A recombinant target-specific signal amplifier was constructed by genetically fusing the enhanced ascorbate peroxidase 2 (APEX2) and an antibody-binding domain (ABD). The fusion protein APEX2-ABD possessed the peroxidase activity and the antibody-binding capability simultaneously and replaced the conventional HRP-conjugated secondary antibodies in a TSA assay for amplifying fluorescence signals.

Covalent conjugation of cysteine-engineered scFv to PEGylated magnetic nanoprobes for immunotargeting of breast cancer cells

Orientation- and site-directed covalent conjugation of cysteine-engineered scFv to PEGylated SPIONs allows antigen recognition while preserving colloidal properties of nanoprobes.

Colloidal Gold--Collagen Protein Core--Shell Nanoconjugate: One-Step Biomimetic Synthesis, Layer-by-Layer Assembled Film, and Controlled Cell Growth

The biogenic synthesis of biomolecule-gold nanoconjugates is of key importance for a broad range of biomedical applications. In this work, a one-step, green, and condition-gentle strategy is presented to synthesize stable colloidal gold-collagen core-shell nanoconjugates in an aqueous solution at room temperature, without use of any reducing agents and stabilizing agents. It is discovered that electrostatic binding between gold ions and collagen proteins and concomitant in situ reduction by hydroxyproline residues are critically responsible for the formation of the core-shell nanoconjugates. The film formed by layer-by-layer assembly of such colloidal gold-collagen nanoconjugates can notably improve the mechanical properties and promote cell adhesion, growth, and differentiation. Thus, the colloidal gold-collagen nanoconjugates synthesized by such a straightforward and clean manner, analogous to a biomineralization pathway, provide new alternatives for developing biologically based hybrid biomaterials toward a range of therapeutic and diagnostic applications.

Facet selectivity in gold binding peptides: exploiting interfacial water structure

Peptide sequences that can discriminate between gold facets under aqueous conditions offer a promising route to control the growth and organisation of biomimetically-synthesised gold nanoparticles. Knowledge of the interplay between sequence, conformations and interfacial properties is essential for predictable manipulation of these biointerfaces, but the structural connections between a given peptide sequence and its binding affinity remain unclear, impeding practical advances in the field. These structural insights, at atomic-scale resolution, are not easily accessed with experimental approaches, but can be delivered via molecular simulation. A current unmet challenge lies in forging links between predicted adsorption free energies derived from enhanced sampling simulations with the conformational ensemble of the peptide and the water structure at the surface. To meet this challenge, here we use an in situ combination of Replica Exchange with Solute Tempering with Metadynamics simulations to predict the adsorption free energy of a gold-binding peptide sequence, AuBP1, at the aqueous Au(111), Au(100)(1 × 1) and Au(100)(5 × 1) interfaces. We find adsorption to the Au(111) surface is stronger than to Au(100), irrespective of the reconstruction status of the latter. Our predicted free energies agree with experiment, and correlate with trends in interfacial water structuring. For gold, surface hydration is predicted as a chief determining factor in peptide-surface recognition. Our findings can be used to suggest how shaped seed-nanocrystals of Au, in partnership with AuBP1, could be used to control AuNP nanoparticle morphology.

Structure and properties of citrate overlayers adsorbed at the aqueous Au(111) interface

One of the most common means of gold nanoparticle (AuNP) biofunctionalization involves the manipulation of precursor citrate-capped AuNPs via ligand displacement. However, the molecular-level structural characteristics of the citrate overlayer adsorbed at the aqueous Au interface at neutral pH remain largely unknown. Access to atomistic-scale details of these interfaces will contribute much needed insight into how AuNPs can be manipulated and exploited in aqueous solution. Here, the structures of such citrate overlayers adsorbed at the aqueous Au(111) interface at pH 7 are predicted and characterized using atomistic molecular dynamics simulations, for a range of citrate surface densities. We find that the overlayers are disordered in the surface density range considered, and that many of their key characteristics are invariant with surface density. In particular, we predict the overlayers to have 3-D, rather than 2-D, morphologies, with the anions closest to the gold surface being oriented with their carboxylate groups pointing away from the surface. We predict both striped and island morphologies for our overlayers, depending on the citrate surface density, and in all cases we find bare patches of the gold surface are present. Our simulations suggest that both citrate-gold adsorption and citrate-counterion pairing contribute to the stability of these citrate overlayer morphologies. We also calculate the free energy of adsorption at the aqueous Au(111) interface of a single citrate molecule, and compare this with the corresponding value for a single arginine molecule. These findings enable us to predict the conditions under which ligand displacement of surface-adsorbed citrate by arginine may take place. Our findings represent the first steps toward elucidating a more elaborate, detailed atomistic-scale model relating to the biofunctionalization of citrate-capped AuNPs.

Targeted approaches for HER2 breast cancer therapy: News from nanomedicine?

About 30% of human breast cancers are human epidermal growth factor receptor 2 (HER2)⁺. This particular biological portrait is characterized by the overexpression of HER2 receptor with the subsequent deregulation of downstream pathways, which control cellular survival and proliferation. The most effective treatment for HER2⁺ cancer is represented by therapy with HER2-targeted agents. Anti-HER2 therapy dramatically improves clinical outcomes, although it shows some limitations in achieving a proper treatment. These drawbacks of HER2-targeted therapy may be overcome with the development of HER2-targeted drug delivery nanodevices. These nanoparticles possess an internal three-dimensional compartimentalization, which allows to combine the specific target recognition with their capability to act as a drug reservoir for the selective delivery of chemotherapics to tumor sites. Moreover, nanoparticles useful in photothermal ablation or in photodynamic therapy have been functionalized in order to match specificity in tumor cell recognition and suitable chemical properties. Here, we summarize the state of the art concerning the HER2⁺ breast cancer and anti-HER2 therapy, in particular deepening the contribution of the nanomedicine. Description of preclinical studies performed with HER2-targeted nanoparticles for HER2⁺ breast cancer therapy will be preceded by an overview on HER2-targeting molecules and nano-conjugation strategies. Further investigation will be necessary to introduce these nano-drugs in clinical practice; however promising results encourage an upcoming translation of this research for the next future.

Ultrasmall biomolecule-anchored hybrid GdVO4 nanophosphors as a metabolizable multimodal bioimaging contrast agent

Multimodal molecular imaging has recently attracted much attention on disease diagnostics by taking advantage of individual imaging modalities. Herein, we have demonstrated a new paradigm for multimodal bioimaging based on amino acids-anchored ultrasmall lanthanide-doped GdVO4 nanoprobes. On the merit of special metal-cation complexation and abundant functional groups, these amino acids-anchored nanoprobes showed high colloidal stability and excellent dispersibility. Additionally, due to typical paramagnetic behaviour, high X-ray mass absorption coefficient and strong fluorescence, these nanoprobes would provide a unique opportunity to develop multifunctional probes for MRI, CT and luminescence imaging. More importantly, the small size and biomolecular coatings endow the nanoprobes with effective metabolisability and high biocompatibility. With the superior stability, high biocompatibility, effective metabolisability and excellent contrast performance, amino acids-capped GdVO4:Eu(3+) nanocastings are a promising candidate as multimodal contrast agents and would bring more opportunities for biological and medical applications with further modifications.

Immobilization of carboxypeptidase from Sulfolobus solfataricus on magnetic nanoparticles improves enzyme stability and functionality in organic media

Background

Superparamagnetic iron oxide nanoparticles (MNP) offer several advantages for applications in biomedical and biotechnological research. In particular, MNP-based immobilization of enzymes allows high surface-to-volume ratio, good dispersibility, easy separation of enzymes from the reaction mixture, and reuse by applying an external magnetic field. In a biotechnological perspective, extremophilic enzymes hold great promise as they often can be used under non-conventional harsh conditions, which may result in substrate transformations that are not achievable with normal enzymes. This prompted us to investigate the effect of MNP bioconjugation on the catalytic properties of a thermostable carboxypeptidase from the hyperthermophilic archaeon Sulfolobus solfataricus (CPSso), which exhibits catalytic properties that are useful in synthetic processes.

Results

CPSso was immobilized onto silica-coated iron oxide nanoparticles via NiNTA-His tag site-directed conjugation. Following the immobilization, CPSso acquired distinctly higher long-term stability at room temperature compared to the free native enzyme, which, in contrast, underwent extensive inactivation after 72 h incubation, thus suggesting a potential utilization of this enzyme under low energy consumption. Moreover, CPSso conjugation also resulted in a significantly higher stability in organic solvents at 40°C, which made it possible to synthesize N-blocked amino acids in remarkably higher yields compared to those of free enzyme.

Conclusions

The nanobioconjugate of CPSso immobilized on silica-coated magnetic nanoparticles exhibited enhanced stability in aqueous media at room temperature as well as in different organic solvents. The improved stability in ethanol paves the way to possible applications of immobilized CPSso, in particular as a biocatalyst for the synthesis of N-blocked amino acids. Another potential application might be amino acid racemate resolution, a critical and expensive step in chemical synthesis.

DNA-mediated biomineralization of rare-earth nanoparticles for simultaneous imaging and stimuli-responsive drug delivery

A DNA-guided method for surface engineering of NaGdF4:Ce/Tb hybrid nanoparticle has been proposed. In this study, the DNA molecules that retained after one-pot NaGdF4:Ce/Tb synthesis is directly utilized as biotemplate for CaP heterogeneous nucleation, thus the dual-purpose function of DNA is realized in the current study which could afford a new type of pH-responsive theranostic platform to enhance the therapeutic efficiency while minimizing side effects. The introduction of another layer of aptamer molecules on CaP facilitated cellular uptake of the resulting nanocomposite into specific target cells via receptor-mediated endocytosis. After been taken by the target tumor cells, the NaGdF4:Ce/Tb@CaP was found to be mostly accumulated in lysosome, which facilitated the dissolving of CaP coatings as non-toxic ions to initiate drug release and efficient cancer cell destruction. We envision that the hybrid nanocarrier may serve as practical and multifunctional probe for cancer therapy and the presented synthesis approach here may also benefit the preparation of many other types of multifunctional inorganic-biomolecular hybrid nanostructures based on the DNA nanotechnology.

Delivering colloidal nanoparticles to mammalian cells: a nano-bio interface perspective

Understanding the behavior of multifunctional colloidal nanoparticles capable of biomolecular targeting remains a fascinating challenge in materials science with dramatic implications in view of a possible clinical translation. In several circumstances, assumptions on structure-activity relationships have failed in determining the expected responses of these complex systems in a biological environment. The present Review depicts the most recent advances about colloidal nanoparticles designed for use as tools for cellular nanobiotechnology, in particular, for the preferential transport through different target compartments, including cell membrane, cytoplasm, mitochondria, and nucleus. Besides the conventional entry mechanisms based on crossing the cellular membrane, an insight into modern physical approaches to quantitatively deliver nanomaterials inside cells, such as microinjection and electro-poration, is provided. Recent hypotheses on how the nanoparticle structure and functionalization may affect the interactions at the nano-bio interface, which in turn mediate the nanoparticle internalization routes, are highlighted. In addition, some hurdles when this small interface faces the physiological environment and how this phenomenon can turn into different unexpected responses, are discussed. Finally, possible future developments oriented to synergistically tailor biological and chemical properties of nanoconjugates to improve the control over nanoparticle transport, which could open new scenarios in the field of nanomedicine, are addressed.

Biogenic growth of alloys and core-shell nanostructures using urease as a nanoreactor at ambient conditions

Biomineralization is an extremely efficient biologically guided process towards the advancement of nano-bio integrated materials. As a prime module of the natural world, enzymes are expected to play a major role in biogenic growth of inorganic nanostructures. Although there have been developments in designing enzyme-responsive nanoparticle systems or generation of inorganic nanostructures in an enzyme-stimulated environment, reports regarding action of enzymes as reducing agents themselves for the growth of inorganic nanoparticles still remains elusive. Here we present a mechanistic investigation towards the synthesis of metal and metallic alloy nanoparticles using a commonly investigated enzyme, Jack bean urease (JBU), as a reducing as well as stabilizing agent under physiological conditions. The catalytic functionality of urease was taken advantage of towards the development of metal-ZnO core-shell nanocomposites, making urease an ideal bionanoreactor for synthesizing higher order nanostructures such as alloys and core- shell under ambient conditions.

Enzymes as bionanoreactors: glucose oxidase for the synthesis of catalytic Au nanoparticles and Au nanoparticle–polyaniline nanocomposites

Biogenic synthesis of Au nanoparticles and Au nanoparticle–polyaniline composite could be accomplished taking advantage of the reducing and catalytic activity of glucose oxidase.

One-step nucleotide-programmed growth of porous upconversion nanoparticles: application to cell labeling and drug delivery

A simple and "green" strategy has been reported for the first time to fabricate upconversion nanoparticles (UCNPs) by utilizing nucleotides as bio-templates. The influence of the functionalities present on the nucleotide on the production of nanoparticles was investigated in detail. Through the effects of nucleotides, the obtained nanoparticles possessed a porous structure. The use of the as-prepared UCNPs for cell imaging, drug delivery and versatile therapy applications were demonstrated. In view of the bright up-conversion luminescence as well as the excellent biocompatibility, and the good colloidal stability of the as-prepared UCNPs, we envision that our synthesis protocol might advance both the fields of UCNPs and biomolecule-based nanotechnology for future studies.

Protein-directed approaches to functional nanomaterials: a case study of lysozyme

Using lysozyme as a model, protein-directed approaches to functional nanomaterials were reviewed, making rational materials design possible in the future.

Enzymatic fabrication of protein-decorated gold nanoparticles by the aid of artificial peptides with gold-binding affinity

Here, we report a new approach for the biofabrication of protein-immobilized gold nanoparticles (Au NPs), using oxidoreductase with gold-binding peptide-tagged recombinant proteins. The reduction of Au ions to Au(0) was achieved using a natural electron-donating cofactor, nicotinamide adenine dinucleotide, which was regenerated by the glycerol dehydrogenase (GLD) enzyme. First, we selected the A3 peptide (AYSSGAPPMPPF) as a gold binding moiety. The A3 peptide was introduced to the C-terminus of fusion proteins of immunoglobulin G (IgG)-binding domains of protein G and protein A. In the presence of the recombinant protein, the GLD-catalyzed cofactor reduction resulted in the efficient in situ fabrication of Au NPs immobilized with the fusion protein. Moreover, the protein-immobilized Au NPs were shown to have IgG binding activity. Although the A3 peptide had the ability to stabilize Au NPs, the results suggested that its binding affinity for Au NPs was unexpectedly weaker than that of His-tag. A cysteine residue was thus introduced to a recombinant protein adjacent to the A3 peptide. Finally, an artificial peptide, comprising A3 sequence with the C-terminal single cysteine residue, enabled the stable display of a fusion protein while maintaining its IgG binding activity through the Au-S bond. This enzyme-assisted one-pot methodology for protein-Au NPs conjugation offers one potent route for the facile fabrication of biomolecule-decorated metal NPs.

Biotechnological approaches toward nanoparticle biofunctionalization

Nanomedicine has emerged in the past decade as a promising tool for several therapeutic and diagnostic applications. The development of nanoconjugates containing bioactive ligands specific for targeting cancer cell receptors has become a primary objective of modern nanotechnology. The design of ideal nanoconjugates requires optimization of fundamental parameters including size, shape, ligand shell composition, and reduction in nonspecific protein adsorption. Of great importance is the choice of bioconjugation approach, given that it affects the orientation, accessibility, and bioactivity of the targeting molecule. We provide an overview of recent advances in the immobilization of targeting proteins, focusing on methods to control ligand orientation and density, and highlight criteria for nanoparticle design and development required to achieve enhanced receptor-targeting efficiency.

Non-natural amino acids containing peptide-capped gold nanoparticles for drug delivery application

Peptide-based capping agents for gold nanoparticles (GNPs) are possible alternatives for capping and derivatizing GNPs, but suffer from a major disadvantage of sensitivity toward non specific proteases, which may limit their in vivo utility. Using non-natural analogs of natural α-amino acids offer an attractive alternate strategy to circumvent this potential bottleneck in realizing full potential of peptide based capping gents for GNPs for biological applications. Here, we have designed and developed pentapeptides containing non-natural amino acid (α,β-dehydrophenylalanine and α-aminoisobutyric acid) as capping agents for GNPs. All these peptides were able to efficiently cap GNPs and peptide induced aggregation was not observed. Peptide capped GNPs showed minimal cytotoxicity to mammalian cell lines (HeLa and L929) as well as mice spleenocytes. They encapsulated small drug like molecules and peptide capped GNPs entrapping drugs were more efficient in killing HeLa cells compared to the free drug. Therefore, these non-natural amino acid containing peptide-capped GNPs may be further developed as alternate drug delivery vehicles.

Assessing the in vivo targeting efficiency of multifunctional nanoconstructs bearing antibody-derived ligands

A great challenge in nanodiagnostics is the identification of new strategies aimed to optimize the detection of primary breast cancer and metastases by the employment of target-specific nanodevices. At present, controversial proof has been provided on the actual importance of surface functionalization of nanoparticles to improve their in vivo localization at the tumor. In the present paper, we have designed and developed a set of multifunctional nanoprobes, modified with three different variants of a model antibody, that is, the humanized monocolonal antibody trastuzumab (TZ), able to selectively target the HER2 receptor in breast cancer cells. Assuming that nanoparticle accumulation in target cells is strictly related to their physicochemical properties, we performed a comparative study of internalization, trafficking, and metabolism in MCF7 cells of multifunctional nanoparticles (MNP) functionalized with TZ or with alternative lower molecular weight variants of the monoclonal antibody, such as the half-chain (HC) and scFv fragments (scFv). Hence, to estimate to what extent the structure of the surface bioligand affects the targeting efficiency of the nanoconjugate, three cognate nanoconstructs were designed, in which only the antibody form was differentiated while the nanoparticle core was maintained unvaried, consisting of an iron oxide spherical nanocrystal coated with an amphiphilic polymer shell. In vitro, in vivo, and ex vivo analyses of the targeting efficiency and of the intracellular fate of MNP-TZ, MNP-HC, and MNP-scFv suggested that the highly stable MNP-HC is the best candidate for application in breast cancer detection. Our results provided evidence that, in this case, active targeting plays an important role in determining the biological activity of the nanoconstruct.

Insights into biogenic and chemical production of inorganic nanomaterials and nanostructures

The synthesis of inorganic nanomaterials and nanostructures by the means of diverse physical, chemical, and biological principles has been developed in recent decades. The nanoscale materials and structures creation continue to be an active area of researches due to the exciting properties of the resulting nanomaterials and their innovative applications. Despite physical and chemical approaches which have been used for a long time to produce nanomaterials, biological resources as green candidates that can replace old production methods have been focused in recent years to generate various inorganic nanoparticles (NPs) or other nanoscale structures. Cost-effective, eco-friendly, energy efficient, and nontoxic produced nanomaterials using diverse biological entities have been received increasing attention in the last two decades in contrast to physical and chemical methods owe using toxic solvents, generate unwanted by-products, and high energy consumption which restrict the popularity of these ways employed in nanometric science and engineering. In this review, the biosynthesis of gold, silver, gold-silver alloy, magnetic, semiconductor nanocrystals, silica, zirconia, titania, palladium, bismuth, selenium, antimony sulfide, and platinum NPs, using bacteria, actinomycetes, fungi, yeasts, plant extracts and also informational bio-macromolecules including proteins, polypeptides, DNA, and RNA have been reported extensively to mention the current status of the biological inorganic nanomaterial production. In other hand, two well-known wet chemical techniques, namely chemical reduction and sol-gel methods, used to produce various types of nanocrystalline powders, metal oxides, and hybrid organic-inorganic nanomaterials have presented.