Folding Induced Assembly of Polypeptide Decorated Gold Nanoparticles

Novel Casein-Derived Peptide-Zinc Chelate: Zinc Chelation and Transepithelial Transport Characteristics

Casein-derived peptides are recognized as promising candidates for improving zinc bioavailability through the form of a peptide-zinc chelate. In the present work, a novel 11-residue peptide TEDELQDKIHP identified from casein hydrolysate in our previous study was synthesized to investigate the zinc chelation characteristics. Meanwhile, the digestion stability and transepithelial transport of TEDELQDKIHP-Zn were also investigated. The obtained results indicated that the carboxyl groups (from Asp and Glu), amino groups (from Lys and His), pyrrole nitrogen group of Pro, and imidazole nitrogen group of His were responsible for zinc chelation. The complexation with zinc resulted in a more ordered structure of TEDELQDKIHP-Zn. In terms of digestion stability, the chelate of TEDELQDKIHP-Zn could remain stable to a large extent after gastric (78.54 ± 0.14%) and intestinal digestion (70.18 ± 0.17%). Moreover, TEDELQDKIHP-Zn was proven to be a well-absorbed biological particle with a P_app value higher than 1 × 10^-6 cm/s, and it could be transported across the intestine epithelium through transcytosis. TEDELQDKIHP-Zn exhibited more bioavailable effects on zinc absorption and ALP activity than inorganic zinc sulfate.

Monovalent ion-mediated charge-charge interactions drive aggregation of surface-functionalized gold nanoparticles

Monolayer-protected metal nanoparticles (NPs) are not only promising materials with a wide range of potential industrial and biological applications, but they are also a powerful tool to investigate the behaviour of matter at nanoscopic scales, including the stability of dispersions and colloidal systems. This stability is dependent on a delicate balance between attractive and repulsive interactions that occur in the solution, and it is described in quantitative terms by the classic Derjaguin-Landau-Vewey-Overbeek (DLVO) theory, that posits that aggregation between NPs is driven by van der Waals interactions and opposed by electrostatic interactions. To investigate the limits of this theory at the nanoscale, where the continuum assumptions required by the DLVO theory break down, here we investigate NP dimerization by computing the Potential of Mean Force (PMF) of this process using fully atomistic MD simulations. Serendipitously, we find that electrostatic interactions can lead to the formation of metastable NP dimers at physiological ion concentrations. These dimers are stabilized by complexes formed by negatively charged ligands belonging to distinct NPs that are bridged by positively charged monovalent ions present in solution. We validate our findings by collecting tomographic EM images of NPs in solution and by quantifying their radial distribution function, that shows a marked peak at interparticle distance comparable with that of MD simulations. Taken together, our results suggest that not only van der Waals interactions, but also electrostatic interactions mediated by monovalent ions at physiological concentrations, contribute to attraction between nano-sized charged objects at very short length scales.

A promising drug delivery candidate (CS-g-PMDA-CYS-fused gold nanoparticles) for inhibition of multidrug-resistant uropathogenic Serratia marcescens

Antibiotic resistance amongst microbial pathogens is a mounting serious issue in researchers and physicians. Various alternatives to overcome the multidrug-resistant bacterial infections are under search, and biofilm growth inhibition is one of them. In this investigation, a polymeric drug delivery system loaded with multi-serratial drugs to improve the delivery of drugs against urinary tract infection causative Serratia marcescens. The chitosan grafted pyromellitic dianhydride - cysteine (CS-g-PMDA-CYS) was conjugated with AuNPs by using the -SH group of CYS and RF (rifampicin) and INH (isoniazid) were loaded in AuNPs-fused CS-g-PMDA-CYS system. Several physicochemical techniques characterized this fabricated AuNPs/RF/INH/CS-g-PMDA-CYS system. The successful encapsulation of RF and INH in AuNPs-fused CS-g-PMDA-CYS polymer had confirmed, and it observed the loading capacity for RF and INH was 9.02% and 13.12%, respectively. The in vitro drug discharge pattern was perceived high in pH 5.5 compared with pH 7.4. The AuNPs/RF/INH/CS-g-PMDA-CYS escalates 74% of Caenorhabditis elegans survival during Serratia marcescens infection by aiming biofilm development and virulence in S. marcescens. Author postulate that the fabricated system is a promising drug carrier and delivery system for inhibition of multidrug-resistant bacterias like S. marcescens.

Antarctic Krill Derived Nonapeptide as an Effective Iron-Binding Ligand for Facilitating Iron Absorption via the Small Intestine

A novel nonapeptide DTDSEEEIR identified from Antarctic krill (Euphausia superba) iron-binding peptides was used in this study to analyze its iron-binding sites and structural changes after iron coordination. The enzymatic resistance and transport of DTDSEEEIR-iron during gastrointestinal digestion and absorption as well as the relationship between the DTDSEEEIR stability and the enhancement of iron absorption were further explored. Results revealed that iron ions spontaneously bound to the carboxyl, hydroxyl, and amino groups of the DTDSEEEIR peptide, which induced the folding of DTDSEEEIR to form a more orderly structure. The DTDSEEEIR peptide remained stable to a certain extent (79.60 ± 0.19%) after gastrointestinal digestion and the coordination of iron improved the digestive stability of the DTDSEEEIR peptide (93.89 ± 1.37%). Moreover, the stability of DTDSEEEIR across intestinal epithelium had a positive effect on iron absorption, which implied that DTDSEEEIR might carry iron ions through intestinal epithelial cells.

Rational Design of Functional Peptide-Gold Hybrid Nanomaterials for Molecular Interactions

Gold nanoparticles (AuNPs) have been extensively used for decades in biosensing-related development due to outstanding optical properties. Peptides, as newly realized functional biomolecules, are promising candidates of replacing antibodies, receptors, and substrates for specific molecular interactions. Both peptides and AuNPs are robust and easily synthesized at relatively low cost. Hence, peptide-AuNP-based bio-nano-technological approaches have drawn increasing interest, especially in the field of molecular targeting, cell imaging, drug delivery, and therapy. Many excellent works in these areas have been reported: demonstrating novel ideas, exploring new targets, and facilitating advanced diagnostic and therapeutic technologies. Importantly, some of them also have been employed to address real practical problems, especially in remote and less privileged areas. This contribution focuses on the application of peptide-gold hybrid nanomaterials for various molecular interactions, especially in biosensing/diagnostics and cell targeting/imaging, as well as for the development of highly active antimicrobial/antifouling coating strategies. Rationally designed peptide-gold nanomaterials with functional properties are discussed along with future challenges and opportunities.

Self-assembled peptide-inorganic nanoparticle superstructures: from component design to applications

Peptides have become excellent platforms for the design of peptide-nanoparticle hybrid superstructures, owing to their self-assembly and binding/recognition capabilities. Morover, peptide sequences can be encoded and modified to finely tune the structure of the hybrid systems and pursue functionalities that hold promise in an array of high-end applications. This feature article summarizes the different methodologies that have been developed to obtain self-assembled peptide-inorganic nanoparticle hybrid architectures, and discusses how the proper encoding of the peptide sequences can be used for tailoring the architecture and/or functionality of the final systems. We also describe the applications of these hybrid superstructures in different fields, with a brief look at future possibilities towards the development of new functional hybrid materials.

Nanoassembled Peptide Biosensors for Rapid Detection of Matrilysin Cancer Biomarker

Early detection of cancer is likely to be one of the most effective means of reducing the cancer mortality rate. Hence, simple and ultra-quick methods for noninvasive detection of early-stage tumors are highly sought-after. In this study, a nanobiosensing platform with a rapid response time of nearly 30 s is introduced for the detection of matrilysin-the salivary gland cancer biomarker-with a limit of detection as low as 30 nm. This sensing platform is based on matrilysin-digestible peptides that bridge gold nanoparticle (AuNPs) cores (≈30-50 nm) and carbon quantum dot (CDs) satellites (≈9 nm). A stepwise synthesis procedure is used for self-assembly of AuNP-peptide-CDs, ensuring their long-term stability. The AuNP-peptide-CDs produce ideal optical signals, with noticeable fluorescence quenching effects. Upon peptide cleavage by matrilysin, CDs leave the surface of AuNPs, resulting in ultra-fast detectable violet and visible fluorescent signals.

Bioinspired Histidine⁻Zn2+ Coordination for Tuning the Mechanical Properties of Self-Healing Coiled Coil Cross-Linked Hydrogels

Natural biopolymeric materials often possess properties superior to their individual components. In mussel byssus, reversible histidine (His)–metal coordination is a key feature, which mediates higher-order self-assembly as well as self-healing. The byssus structure, thus, serves as an excellent natural blueprint for the development of self-healing biomimetic materials with reversibly tunable mechanical properties. Inspired by byssal threads, we bioengineered His–metal coordination sites into a heterodimeric coiled coil (CC). These CC-forming peptides serve as a noncovalent cross-link for poly(ethylene glycol)-based hydrogels and participate in the formation of higher-order assemblies via intermolecular His–metal coordination as a second cross-linking mode. Raman and circular dichroism spectroscopy revealed the presence of α-helical, Zn²⁺ cross-linked aggregates. Using rheology, we demonstrate that the hydrogel is self-healing and that the addition of Zn²⁺ reversibly switches the hydrogel properties from viscoelastic to elastic. Importantly, using different Zn²⁺:His ratios allows for tuning the hydrogel relaxation time over nearly three orders of magnitude. This tunability is attributed to the progressive transformation of single CC cross-links into Zn²⁺ cross-linked aggregates; a process that is fully reversible upon addition of the metal chelator ethylenediaminetetraacetic acid. These findings reveal that His–metal coordination can be used as a versatile cross-linking mechanism for tuning the viscoelastic properties of biomimetic hydrogels.

AuNP-peptide probe for caspase-3 detection in living cells by SERS

Colloidal nanoparticles can be used as surface-enhanced Raman scattering (SERS) substrates because the very close spacing between particles existing in these colloidal systems is beneficial for the generation of extremely strong and highly spatially localized electric field enhancements. Herein, a caspase-3-specified peptide was used as a molecular cross-linker to engineer gold nanoparticle (AuNP) junctions in a controllable manner. The peptide was designed with a sequence of CCALNNPFFDVED (Cys-Cys-Ala-Leu-Asn-Asn-Pro-Phe-Phe-Asp-Val-Glu-Asp) or CCALNNKYDDVED (Cys-Cys-Ala-Leu-Asn-Asn-Lys-Tyr-Asp-Asp-Val-Glu-Asp), where the CALNN (Cys-Ala-Leu-Asn-Asn) fragment helps to stabilize AuNP suspension in aqueous media and the sequence of DVED (Asp-Glu-Val-Asp) can be cleaved by caspase-3. In addition, the PFF (Pro-Phe-Phe) or KYD (Lys-Tyr-Asp) was exposed and interacted via the hydrophobic or alternate negative and positive electro-interaction in the presence of caspase-3, inducing the aggregation of colloidal Au-peptides accompanied with the enhancement of SERS. It can be observed that the SERS-enhanced signals were correlated with the caspase-3 concentrations and the limit of detection can reach 1.5 ng mL^-1. Finally, this caspase-3-specified AuNP-peptide probe has been found to be a promising candidate for its application in the analysis of caspase-3 in living cells.

Modular Assembly of Plasmonic Nanoparticles Assisted by DNA Origami

Arraying noble metal nanoparticles with nanoscale features is an important way to develop plasmonic devices with novel optical properties such as plasmonic chiral metamolecules, optical waveguides, and so forth. Along with top-down methods of fabricating plasmonic nanostructures, solution-based self-assembly provides an alternative approach. There are mainly two routes to organizing metal nanoparticles via self-assembly. One is directly linking nanoparticles through linker molecules, and the other is using nanoparticles to decorate a preformed template. We combine these two routes and herein report a strategy for the DNA origami-assisted modular assembly of gold nanoparticles into homogeneous and heterogeneous plasmonic nanostructures. For each module, we designed W-shaped DNA origami with two troughs as two domains. One domain is used to host a gold nanoparticle, and the other domain is designed to capture another gold nanoparticle hosted on a different module. By simply tuning the sequences of capture DNA strands on each module, gold nanoparticles including spherical and rod-shaped gold nanoparticles (denoted as AuNPs and AuNRs) could be well organized in a predefined manner to form versatile plasmonic nanostructures. Since the interparticle distances could be precisely controlled at the nanoscale, we also studied the plasma coupling among the assembled plasmonic nanostructures. This modular assembly strategy represents a simple yet general and effective design principle for DNA-assembled plasmonic nanostructures.

Self-Assembly of a Structurally Defined Chiro-Optical Peptide-Oligothiophene Hybrid Material

Conducting polymers are routinely used in optoelectronic biomaterials, but large polymer polydispersity and poor aqueous compatibility complicate integration with biomolecular templates and development of discrete and defined supramolecular complexes. Herein, we report on a chiro-optical hybrid material generated by the self-assembly of an anionic peptide and a chemically defined cationic pentameric thiophene in aqueous environment. The peptide acts as a stereochemical template for the thiophene and adopts an α-helical conformation upon association, inducing optical activity in the thiophene π-π* transition region. Theoretical calculations confirm the experimentally observed induced structural changes and indicate the importance of electrostatic interactions in the complex. The association process is also probed at the substrate-solvent interface using peptide-functionalized gold nanoparticles, indicating that the peptide can also act as a scaffold when immobilized, resulting in structurally well-defined supramolecular complexes. The hybrid complex could rapidly be assembled, and the kinetics of the formation could be monitored by utilizing the local surface plasmon resonance originating from the gold nanoparticles. We foresee that these findings will aid in designing novel hybrid materials and provide a possible route for the development of functional optoelectronic interfaces for both biomaterials and energy harvesting applications.

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

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

Design and Characterization of Fibers and Bionanocomposites Using the Coiled-Coil Domain of Cartilage Oligomeric Matrix Protein

Tremendous effort has been dedicated to the design and assembly of bioinspired protein-based architectures with potential applications in drug delivery, tissue engineering, biosensing, and bioimaging. Here, we describe our strategy to generate fibers and bionanocomposites using the coiled-coil domain of cartilage oligomeric matrix protein (COMPcc). Our construct, Q, engineered by swapping particular regions of COMPcc to optimize surface charge, self-assembles to form nanofibers. The Q protein nanofibers can efficiently bind curcumin to form robust mesofibers that can be potentially used for drug delivery and biomedical applications. In addition, using the same Q protein, we describe the biotemplation of gold nanoparticles (AuNP) in the presence and absence of the hexahistidine tag (His-tag). The Q bearing His-tag·AuNP (Q·AuNP) readily deposits on electrode surfaces, while Q without His-tag·AuNP (Qx·AuNP) stabilizes the soluble protein·gold bionanocomposites for several days without aggregating.

Detection of chymase activity using a specific peptide probe conjugated onto gold nanoparticles

The gold nanoparticles (AuNPs) peptide probe functionalized with specific peptide sequences was developed for the sensitive and efficient detection of chymase activity.

Synthesis and characterization of magnetite nanoparticles having different cover layer and investigation of cover layer effect on the adsorption of lysozyme and bovine serum albumin

In this study, differently coated superparamagnetic Fe₃O₄ (magnetite) nanoparticles were synthesized, characterized and used for lysozyme (Ly) and bovine serum albumin (BSA) adsorption. SiO₂, carbon nanotubes (CNTs) and graphene were used for covering the readily synthesized magnetite nanoparticles to elucidate the effect of cover layer on the protein adsorption kinetics and capacities of nanostructure. XRD, FTIR, AFM, SEM, VSM and fluorescence measurements were used for the characterization of the samples and investigating the adsorption kinetics of Ly and BSA by these nanoparticles. The average particle size of the Fe₃O₄ nanoparticles are approximately found as 10nm and VSM measurement shows that the Fe₃O₄ particles have superparamagnetic behavior with no hysteresis and remnant. The adsorption kinetic of proteins on nanosized material is followed via fluorescence method. All the nanostructures with different cover layers obey pseudo first order kinetics and SiO₂ coated nanoparticles show the fastest kinetics and capabilities for Ly and BSA adsorption.

Nanoparticles assemblies on demand: Controlled aggregation of Ag(0) mediated by modified peptoid sequences

Assemblies of metal nanoparticles (NPs) have been broadly used for the construction of materials with distinct spectroscopic properties towards sensing applications. On the other hand, well-dispersed NPs are exploit for applications in catalysis and medicine. Biopolymers or biomimetic oligomers can serve both as efficient stabilizers of NPs and as useful aggregation mediators that can lead to assemblies with unique properties. Controlling aggregation processes, however, is still challenging and often relies on trial and error rather than on defined thumb rules. Herein we develop specific guidelines for the controlled aggregation of Ag(0) NPs at room temperature in water near neutral pH and without any additives. We use short peptide mimics, N-substituted glycine oligomers called peptoids, as mediators, and investigate the influence of sequences variations on the NPs assembly. Spectroscopic and electron microscopy data reveal that both the length of the peptoids and their sequences have an effect on the NPs aggregation. Thus, we demonstrate that we can control both the degree of aggregation and the aggregates sizes by tuning these properties. Specifically we show that longer peptoid sequences as well as sequences consisting of aromatic side chains are required for the formation of uniform NPs assemblies in an average size of 70nm, while a short hydrophilic sequence can stabilize well-dispersed Ag(0) NPs. Moreover, the catalytic activity of Ag(0) NPs towards the reduction of 4-nitrophenol to 4-aminophenol can be also controlled by varying the properties of the peptoid mediators.

Folding driven self-assembly of a stimuli-responsive peptide-hyaluronan hybrid hydrogel

Protein-metal ion interactions are ubiquitous in nature and can be utilized for controlling the self-assembly of complex supramolecular architectures and materials. Here, a tunable supramolecular hydrogel is described, obtained by self-assembly of a Zn²⁺-responsive peptide-hyaluronic acid hybrid synthesized using strain promoted click chemistry. Addition of Zn²⁺ triggers folding of the peptides into a helix-loop-helix motif and dimerization into four-helix bundles, resulting in hydrogelation. Removal of the Zn²⁺ by chelators results in rapid hydrogel disassembly. Degradation of the hydrogels can also be time-programed by encapsulation of a hydrolyzing enzyme within the gel, offering multiple possibilities for modulating materials properties and release of encapsulated species. The hydrogel further shows potential antioxidant properties when evaluated using an in vitro model for reactive oxygen species.

Peptide Functionalized Gold Nanoparticles as a Stimuli Responsive Contrast Medium in Multiphoton Microscopy

There is a need for biochemical contrast mediators with high signal-to-noise ratios enabling noninvasive biomedical sensing, for example, for neural sensing and protein-protein interactions, in addition to cancer diagnostics. The translational challenge is to develop a biocompatible approach ensuring high biochemical contrast while avoiding a raise of the background signal. We here present a concept where gold nanoparticles (AuNPs) can be utilized as a stimuli responsive contrast medium by chemically triggering their ability to exhibit multiphoton-induced luminescence (MIL) when performing multiphoton laser scanning microscopy (MPM). Proof-of-principle is demonstrated using peptide-functionalized AuNPs sensitive to zinc ions (Zn²⁺). Dispersed particles are invisible in the MPM until addition of millimolar concentrations of Zn²⁺ upon which MIL is enabled through particle aggregation caused by specific peptide interactions and folding. The process can be reversed by removal of the Zn²⁺ using a chelator, thereby resuspending the AuNPs. In addition, the concept was demonstrated by exposing the particles to matrix metalloproteinase-7 (MMP-7) causing peptide digestion resulting in AuNP aggregation, significantly elevating the MIL signal from the background. The approach is based on the principle that aggregation shifts the plasmon resonance, elevating the absorption cross section in the near-infrared wavelength region enabling onset of MIL. This Letter demonstrates how biochemical sensing can be obtained in far-field MPM and should be further exploited as a future tool for noninvasive optical biosensing.

α-Helical peptide vesicles with chiral membranes as enantioselective nanoreactors

We report peptide vesicles with chiral membranes as enantioselective nanoreactors.

Aggregation of inorganic nanoparticles mediated by biomimetic oligomers

Assemblies of nanoparticles (NPs) have been broadly used for the construction of materials with unique spectroscopic and chiral properties for applications in various scientific disciplines such as sensing, bio-nanotechnology and medicine. Mediating the aggregation of NPs by synthetic biomimetic oligomers, namely, DNA, PNA, peptides and peptide mimics, rather than by small organic molecules has been shown to produce interesting supramolecular structures and enable the combination of the biocompatibility of the mediators and the spectroscopic properties of the NPs. Yet, the key to using this powerful approach for designing new functional materials is to understand the NPs aggregation patterns induced by biopolymers and biomimetic oligomers. Herein we describe the important developments in this field, from early studies to recent work with an emphasis on synthetic methods and tools for controlled assembly of metal NPs by biomimetic polymers and oligomers.

Colorimetric Detection of Small Molecules in Complex Matrixes via Target-Mediated Growth of Aptamer-Functionalized Gold Nanoparticles

A versatile and sensitive colorimetric assay that allows the rapid detection of small-molecule targets using the naked eye is demonstrated. The working principle of the assay integrates aptamer-target recognition and the aptamer-controlled growth of gold nanoparticles (Au NPs). Aptamer-target interactions modulate the amount of aptamer strands adsorbed on the surface of aptamer-functionalized Au NPs via desorption of the aptamer strands when target molecules bind with the aptamer. Depending on the resulting aptamer coverage, Au NPs grow into morphologically varied nanostructures, which give rise to different colored solutions. Au NPs with low aptamer coverage grow into spherical NPs, which produce red-colored solutions, whereas Au NPs with high aptamer coverage grow into branched NPs, which produce blue-colored solutions. We achieved visible colorimetric response and nanomolar detection limits for the detection of ochratoxin A (1 nM) in red wine samples, as well as cocaine (1 nM) and 17β-estradiol (0.2 nM) in spiked synthetic urine and saliva, respectively. The detection limits were well within clinically and physiologically relevant ranges, and below the maximum food safety limits. The assay is highly sensitive, specific, and able to detect an array of analytes rapidly without requiring sophisticated equipment, making it relevant for many applications, such as high-throughput drug and clinical screening, food sampling, and diagnostics. Furthermore, the assay is easily adapted as a chip-based platform for rapid and portable target detection.

Generic phosphatase activity detection using zinc mediated aggregation modulation of polypeptide-modified gold nanoparticles

A challenge in the design of plasmonic nanoparticle-based colorimetric assays is that the change in colloidal stability, which generates the colorimetric response, is often directly linked to the biomolecular recognition event. New assay strategies are hence required for every type of substrate and enzyme of interest. Here, a generic strategy for monitoring of phosphatase activity is presented where substrate recognition is completely decoupled from the nanoparticle stability modulation mechanism, which enables detection of a wide range of enzymes using different natural substrates with a single simple detection scheme. Phosphatase activity generates inorganic phosphate that forms an insoluble complex with Zn(2+). In a sample containing a preset concentration of Zn(2+), phosphatase activity will markedly reduce the concentration of dissolved Zn(2+) from the original value, which in turn affects the aggregation of gold nanoparticles functionalized with a designed Zn(2+) responsive polypeptide. The change in nanoparticle stability thus provides a rapid and sensitive readout of the phosphatase activity. The assay is not limited to a particular enzyme or enzyme substrate, which is demonstrated using three completely different phosphatases and five different substrates, and thus constitutes a highly interesting system for drug screening and diagnostics.

Can small hydrophobic gold nanoparticles inhibit β₂-microglobulin fibrillation?

Inorganic nanoparticles stabilized by a shell of organic ligands can enhance or suppress the natural propensity of proteins to form fibrils. Functionalization facilitates targeted delivery of the nanoparticles to various cell types, bioimaging, drug delivery and other therapeutic and diagnostic applications. In this study, we provide a computational model of the effect of a prototypical thiol-protected gold nanoparticle, Au₂₅L₁₈(-) (L = S(CH₂)₂Ph) on the β₂-microglobulin natural fibrillation propensity. To reveal the molecular basis of the protein-nanoparticle association process, we performed various simulations at multiple levels (Classical Molecular Dynamics and Brownian Dynamics) that cover multiple length- and timescales. The results provide a model of the ensemble of structures constituting the protein-gold nanoparticle complexes, and insights into the driving forces for the binding of β₂-microglobulin to hydrophobic small size gold nanoparticles. We have found that the small nanoparticles can bind the protein to form persistent complexes. This binding of nanoparticles is able to block the active sites of domains from binding to another protein, thus leading to potential inhibition of the fibrillation activity. A comparison with the binding patches identified for the interaction of the protein with a known inhibitor of fibrillation, supports our conclusion.

Biofunctionalized gold nanoparticles for colorimetric sensing of botulinum neurotoxin A light chain

Botulinum neurotoxin is considered as one of the most toxic food-borne substances and is a potential bioweapon accessible to terrorists. The development of an accurate, convenient, and rapid assay for botulinum neurotoxins is therefore highly desirable for addressing biosafety concerns. Herein, novel biotinylated peptide substrates designed to mimic synaptosomal-associated protein 25 (SNAP-25) are utilized in gold nanoparticle-based assays for colorimetric detection of botulinum neurotoxin serotype A light chain (BoLcA). In these proteolytic assays, biotinylated peptides serve as triggers for the aggregation of gold nanoparticles, while the cleavage of these peptides by BoLcA prevents nanoparticle aggregation. Two different assay strategies are described, demonstrating limits of detection ranging from 5 to 0.1 nM of BoLcA with an overall assay time of 4 h. These hybrid enzyme-responsive nanomaterials provide rapid and sensitive detection for one of the most toxic substances known to man.

From a Laboratory Exercise for Students to a Pioneering Biosensing Technology

Surface plasmon resonance (SPR) for biosensing was demonstrated 30 years ago. In the present contribution, its general background is described together with the necessary developments both in instrumentation and surface chemistry, leading to the final so-called BIAcore technology. The description is naturally colored by my personal opinion of the developments. SPR for the elucidation of organic mono- and multilayers introduced at the end of the 1970s formed the basis for the first biosensing demonstration of SPR in the beginning of the 1980s. It is pointed out how the need of an up-to-date laboratory exercise for the undergraduate students and the multidisciplinary environment at the Laboratory of Applied Physics at Linköping University led to this demonstration. The initial experiments are touched upon and the further developments at Pharmacia, which led to the BIAcore technology, are described in some details. Some of the present activities in Linköping related to optical biosensing with ubiquitous instrumentation are also described, including SPR detection with a computer screen and a web camera and most recently with a cellular phone.

Effects of silica nanoparticle supported ionic liquid as additive on thermal reversibility of human carbonic anhydrase II

Silica nanoparticle supported imidazolium ionic liquid [SNImIL] was synthesized and utilized as a biocompatible additive for studying the thermal reversibility of human carbonic anhydrase II (HCA II). For this purpose, we prepared additive by modification of nanoparticles through the grafting of ionic liquids on the surface of nanoparticles (SNImIL). The SNImIL were fully characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and thermo gravimetric analysis. The characterization of HCA II was investigated by various techniques including UV-vis and ANS fluorescence spectrophotometry, differential scanning calorimetry, and docking study. SNImIL induced disaggregation, enhanced protein stability and increased thermal reversibility of HCA II by up to 42% at pH 7.75.

Toxicology of nanoparticles

While nanotechnology and the production of nanoparticles are growing exponentially, research into the toxicological impact and possible hazard of nanoparticles to human health and the environment is still in its infancy. This review aims to give a comprehensive summary of what is known today about nanoparticle toxicology, the mechanisms at the cellular level, entry routes into the body and possible impacts to public health. Proper characterisation of the nanomaterial, as well as understanding processes happening on the nanoparticle surface when in contact with living systems, is crucial to understand possible toxicological effects. Dose as a key parameter is essential in hazard identification and risk assessment of nanotechnologies. Understanding nanoparticle pathways and entry routes into the body requires further research in order to inform policy makers and regulatory bodies about the nanotoxicological potential of certain nanomaterials.

Polypeptide folding-mediated tuning of the optical and structural properties of gold nanoparticle assemblies

Responsive hybrid nanomaterials with well-defined properties are of significant interest for the development of biosensors with additional applications in tissue engineering and drug delivery. Here, we present a detailed characterization using UV-vis spectroscopy and small angle X-ray scattering of a hybrid material comprised of polypeptide-decorated gold nanoparticles with highly controllable assembly properties. The assembly is triggered by a folding-dependent bridging of the particles mediated by the heteroassociation of immobilized helix-loop-helix polypeptides and a complementary nonlinear polypeptide present in solution. The polypeptides are de novo designed to associate and fold into a heterotrimeric complex comprised of two disulfide-linked four-helix bundles. The particles form structured assemblies with a highly defined interparticle gap (4.8±0.4 nm) that correlates to the size of the folded polypeptides. Transitions in particle aggregation dynamics, mass-fractal dimensions and ordering, as a function of particle size and the concentration of the bridging polypeptide, are observed; these have significant effects on the optical properties of the assemblies. The assembly and ordering of the particles are highly complex processes that are affected by a large number of variables including the number of polypeptides bridging the particles and the particle mobility within the aggregates. A fundamental understanding of these processes is of paramount interest for the development of novel hybrid nanomaterials with tunable structural and optical properties and for the optimization of nanoparticle-based colorimetric biodetection strategies.

Beauty is skin deep: a surface monolayer perspective on nanoparticle interactions with cells and bio-macromolecules

Surface recognition of biosystems is a critical component in the development of novel biosensors and delivery vehicles, and for the therapeutic regulation of biological processes. Monolayer-protected nanoparticles present a highly versatile scaffold for selective interaction with bio-macromolecules and cells. Through the engineering of the monolayer surface, nanoparticles can be tailored for surface recognition of biomolecules and cells. This review highlights recent progress in nanoparticle-bio-macromolecule/cellular interactions, emphasizing the effect of the surface monolayer structure on the interactions with proteins, DNA, and cell surfaces. The extension of these tailored interactions to hybrid nanomaterials, biosensing platforms, and delivery vehicles is also discussed.