A simple assay to probe disease-associated enzyme activity using glycosaminoglycan-assisted synthesized gold nanoparticles

An ultrasensitive FRET-based fluorescent low molecular weight heparin nanoprobe for quantifying heparanase activity

Heparanase (HPA) is a multifaceted endo-β-glucuronidase, and its dysregulation facilitates cancer metastasis. Developing techniques for fast and sensitively monitoring HPA enzymatic activity is crucial for searching for molecular therapies targeting HPA. Herein, we developed a novel fluorescence resonance energy transfer (FRET)-based nanoprobe AuNCs-LMWH-AuNRs, with AuNCs@GSH-cys and AuNRs/end-NH₂/side-SiO₂ attached to the non-reducing terminus and reducing terminus of low molecular weight heparin (LMWH), respectively. AuNCs@GSH-cys exhibited an absolute quantum yield of 1.1%. The absorption spectra of AuNRs/end-NH₂/side-SiO₂ (825 nm for maximum longitudinal absorption) and the emission spectra of AuNCs@GSH-cys (824 nm for maximum emission) were precisely overlapping, further enhancing the efficiency of FRET. In the presence of HPA, the LMWH nanoprobe exhibited an ultrasensitive response with excitation/emission wavelength (lambda (ex) = 560 nm, lambda (em) = 824 nm). The probe presented a wide linear dynamic detection range (LDR) of 0.125 ng/μL - 0.01 μg/μL in vitro with a limit of detection (LODs) of 82.15 pM (0.43 pg/μL). The excellent selectivity and good fluorescence turn-on efficiency of the probe made it possible for one-step detection of cellular heparanase activity. High throughput screening of HPA inhibitors also can be accomplished using the highly efficient LMWH nanoprobe.

Biomolecule conjugated inorganic nanoparticles for biomedical applications: A review

Last decade has witnessed impressive progress in the fields of medicine and bioengineering with the aid of nanomaterials. Nanomaterials are favoured for their improved bio-chemical as well as mechanical properties with tremendous applications in biomedical domains such as disease diagnosis, targeted drug delivery, medical imaging, in vitro diagnostics, designing innovatory cross-functional implants and regenerative tissue engineering. The current situation insists upon crafting nanotools that are capable of catering to biological needs and construct more efficient biomedical strategies. In the recent years, surface functionalization and capping with biomolecules has initiated substantial interest towards research. In this regard, search of suitable biofunctionalized nanoparticles seem to be like finding pearls from ocean. Conjugating biological molecules with inorganic materials has paved the way for unravelling innovative functional materials with dramatically improved properties and a wide range of uses. Inorganic nanoparticles such as metals, metal oxides, as well as quantum dots have been hybridised or conjugated with biomolecules such as proteins, peptides, carbohydrates, and nucleic acids. The present review reports on various biomolecule functionalized inorganic nanomaterials highlighting the biomolecule-inorganic nanoparticle interaction studies, the mechanism of functionalization, antimicrobial efficacy of the functionalised nanoconjugates and its use in various biomedical applications.

The Development of Assays for Heparanase Enzymatic Activity: Towards a Gold Standard

The enzyme heparanase, an endo-β-glucuronidase, degrades heparan sulfate (HS) chains on the cell surface and in the extracellular matrix. Heparanase regulates numerous biological processes that drive tumour growth, metastasis and angiogenesis. In addition to its key role in cancer progression, it has also been implicated in an ever-growing number of other diseases, particularly those associated with inflammation. The importance of heparanase in biology has led to numerous efforts over the years to develop assays to monitor its activity and to screen for new inhibitors as potential drug candidates. Despite these efforts and the commercialization of a few kits, most heparanase assays are still complex, labour intensive, costly or have limited application. Herein we review the various methods for assaying heparanase enzymatic activity, focusing on recent developments towards new assays that hold the promise of accelerating research into this important enzyme.

Heparin triggered dose dependent multi-color emission switching in water: a convenient protocol for heparinase I estimation in real-life biological fluids

Oligo(p-phenylenevinylene) based bis-pyridinium derivatives show 'ratiometric' detection of heparin in water. For the first time, we present a dose-dependent, multi-color emission switching in the presence of heparin. The reversible self-assembly of probes with heparin as the stimulus is also exploited for the screening of heparinase I enzyme.

Gold nanoparticle-based colorimetric biosensors

Gold nanoparticles (AuNPs) provide excellent platforms for the development of colorimetric biosensors as they can be easily functionalised, displaying different colours depending on their size, shape and state of aggregation. In the last decade, a variety of biosensors have been developed to exploit the extent of colour changes as nano-particles (NPs) either aggregate or disperse, in the presence of analytes. Of critical importance to the design of these methods is that the behaviour of the systems has to be reproducible and predictable. Much has been accomplished in understanding the interactions between a variety of substrates and AuNPs, and how these interactions can be harnessed as colorimetric reporters in biosensors. However, despite these developments, only a few biosensors have been used in practice for the detection of analytes in biological samples. The transition from proof of concept to market biosensors requires extensive long-term reliability and shelf life testing, and modification of protocols and design features to make them safe and easy to use by the population at large. Developments in the next decade will see the adoption of user friendly biosensors for point-of-care and medical diagnosis as innovations are brought to improve the analytical performances and usability of the current designs. This review discusses the mechanisms, strategies, recent advances and perspectives for the use of AuNPs as colorimetric biosensors.

Glyconanomaterials for biosensing applications

Nanomaterials constitute a class of structures that have unique physiochemical properties and are excellent scaffolds for presenting carbohydrates, important biomolecules that mediate a wide variety of important biological events. The fabrication of carbohydrate-presenting nanomaterials, glyconanomaterials, is of high interest and utility, combining the features of nanoscale objects with biomolecular recognition. The structures can also produce strong multivalent effects, where the nanomaterial scaffold greatly enhances the relatively weak affinities of single carbohydrate ligands to the corresponding receptors, and effectively amplifies the carbohydrate-mediated interactions. Glyconanomaterials are thus an appealing platform for biosensing applications. In this review, we discuss the chemistry for conjugation of carbohydrates to nanomaterials, summarize strategies, and tabulate examples of applying glyconanomaterials in in vitro and in vivo sensing applications of proteins, microbes, and cells. The limitations and future perspectives of these emerging glyconanomaterials sensing systems are furthermore discussed.

Preparation of highly luminescent mannose-gold nanodots for detection and inhibition of growth of Escherichia coli

In this paper, we describe a novel, simple, and convenient method for preparing water-soluble biofunctional gold nanodots (Au NDs) for the sensitive and selective detection of Escherichia coli (E. coli) and the inhibition of its growth. We obtained luminescent mannose-capped Au NDs (Man-Au NDs) from as-prepared 2.9-nm Au nanoparticles (Au NPs) and 29,29'-dithio bis(3',6',9',12',15',18'-hexaoxa-nonacosyl α-D-mannopyranoside) (Man-RSSR-Man). To obtain improved quantum yield (>20%), luminescent Man-Au NDs (1.8 nm) were prepared from Au NPs (0.47 μM) and Man-RSSR-Man (2.5 mM) in the presence of sodium borohydride (NaBH(4); 1.0 mM). The highly luminescent properties of Man-Au NDs prepared by the NaBH(4)-assisted method were characterized by UV-vis absorption, photoluminescence, and X-ray photoelectron spectroscopies. The results supported the high-density coverage of the NDs surface by Man-RS ligands. Multivalent interactions between Man-Au NDs and FimH proteins located on the bacterial pili of E. coli resulted in the formation of aggregated cell clusters. After concentrating this agglutinative E. coli from a large-volume cell solution (5 mL), Man-Au NDs were displaced by mannose (100 mM) and stabilized by Man-RSSR-Man (5 mM). Monitoring the luminescence of Man-Au NDs allowed the detection of E. coli at levels as low as 150 CFU/mL. Man-Au NDs were also found to be efficient antibacterial agents, selectively inhibiting the growth of E. coli through Man-Au ND-induced agglutination. Our small-diameter Man-Au NDs, which provided an ultra high ligand density (local concentration) of mannose units for multivalent interactions with E. coli, have great potential for use as an antibacterial agent in other applications.

Glyconanoparticles: multifunctional nanomaterials for biomedical applications

Metal-based glyconanoparticles (GNPs) are biofunctional nanomaterials that combine the unique physical, chemical and optical properties of the metallic nucleus with the characteristics of the carbohydrate coating. The latter characteristics comprise a series of advantages that range from ensuring water solubility, biocompatibility and stability to targeting properties. The selection of suitable carbohydrates for specifically targeting biomarkers opens up the possibility to employ metallic GNPs in diagnostics and/or therapy. Within the vast nanoscience field, this review intends to focus on the advances of multifunctional and multimodal GNPs, which make use of the ‘glycocode’ to specifically address pathogens or pathological-related biomedical problems. Examples of their potential application in antiadhesion therapy and diagnosis are highlighted. From the ex vivo diagnostic perspective, it can be predicted that GNPs will soon be used clinically. However, the in vivo application of metallic GNPs in humans will probably need more time. In particular, major concerns regarding nanotoxicity need to be exhaustively addressed. However, it is expected that the sugar shell of GNPs will lower the intrinsic toxicity of metal nanoclusters better than other non-natural coatings.

Multifunctional nanoscale platforms for targeting of the cancer cell immortality spectrum

In the post-genomic era, "omics" platforms and cancer systems biology are greatly advancing our knowledge of the molecular and cellular underpinnings of cancer. In this article, we begin by outlining the factors governing the development of cancer (tumorigenesis) and use this framework to motivate the need for systems-approaches to cancer diagnostics and therapeutics. We review recent efforts to tap into the remarkable potential of nanotechnology for (i) systems-surveillance (or "sensing") of the molecular signatures of tumorigenesis, and (ii) spatiotemporally-regulated delivery (or "targeting") of combination therapeutics to cancer cells. Specifically, we highlight the salient role of polymeric biomaterials and describe the physicochemical characteristics that render them attractive for the design of such nanoscale platforms. We conclude with discussions on the emerging role of macromolecular biophysics and computational nanotechnology in engineering spatiotemporally-regulated anti-cancer systems.

Colorimetric protein sensing by controlled assembly of gold nanoparticles functionalized with synthetic receptors

A novel strategy is described for the colorimetric sensing of proteins, based on polypeptide-functionalized gold nanoparticles. Recognition is accomplished using a polypeptide sensor scaffold designed to specifically bind to the model analyte, human carbonic anhydrase II (HCAII). The extent of particle aggregation, induced by the Zn(2+)-triggered dimerization and folding of a second polypeptide also present on the surface of the gold nanoparticle, gives a readily detectable colorimetric shift that is dependent on the concentration of the target protein. In the absence of HCAII, particle aggregation results in a major redshift of the plasmon peak, whereas analyte binding prevented the formation of dense aggregates, significantly reducing the magnitude of the redshift. The versatility of the technique is demonstrated using a second model system based on the recognition of a peptide sequence from the tobacco mosaic virus coat protein (TMVP) by a recombinant antibody fragment (Fab57P). Concentrations down to approximately 10 nM and approximately 25 nM are detected for HCAII and Fab57P, respectively. This strategy is proposed as a generic platform for robust and specific protein analysis that can be further developed to monitor a wide range of target proteins.