Heterofunctional nanomaterials: fabrication, properties and applications in nanobiotechnology

Nanomagnet-facilitated pharmaco-compatibility for cancer diagnostics: Underlying risks and the emergence of ultrasmall nanomagnets

Cancer therapy is a fast-emerging biomedical paradigm that elevates the diagnostic and therapeutic potential of a nanovector for identification, monitoring, targeting, and post-treatment response analysis. Nanovectors of superparamagnetic iron oxide nanoparticles (SPION) are of tremendous significance in cancer therapy because of their inherited high surface area, high reactivity, biocompatibility, superior contrast, and magnetic and photo-inducibility properties. In addition to a brief introduction, we summarize various progressive aspects of nanomagnets pertaining to their production with an emphasis on sustainable biomimetic approaches. Post-synthesis particulate and surface alterations in terms of pharmaco-affinity, liquid accessibility, and biocompatibility to facilitate cancer therapy are highlighted. SPION parameters including particle contrast, core-fusions, surface area, reactivity, photosensitivity, photodynamics, and photothermal properties, which facilitate diverse cancer diagnostics, are discussed. We also elaborate on the concept of magnetism to selectively focus chemotherapeutics on tumors, cell sorting, purification of bioentities, and elimination of toxins. Finally, while addressing the toxicity of nanomaterials, the advent of ultrasmall nanomagnets as a healthier alternative with superior properties and compatible cellular interactions is reviewed. In summary, these discussions spotlight the versatility and integration of multi-tasking nanomagnets and ultrasmall nanomagnets for diverse cancer theragnostics.

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SPION synthesis with ascribed prominence on sustainable procedures.

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Particulate species, composition, and surface alteration-enabled theragnostics are highlighted.

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Inherent properties of SPIONs facilitating cancer diagnostics are elaborated.

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Magnetism-based “chemotherapeutics,” cell-sorting, and bioentity purification are emphasized.

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Emergence of ultrasmall SPIONs as a healthier option is summarized.

Inactivation of Escherichia coli planktonic cells by multi-walled carbon nanotubes in suspensions: Effect of surface functionalization coupled with medium nutrition level

While earlier studies have identified the antibacterial activity of carbon nanotubes (CNTs) and proposed that cell membrane damage by direct contact with CNTs is likely the main toxicity mechanism, the relative importance of chemical versus physical properties of CNTs in controlling their bacterial cytotoxicity is understudied. Given that CNT is commonly modified via acid treatment to enhance its dispersivity and surface chemistry, in this study commercially available multi-walled carbon nanotubes (MWCNTs) with high purity were processed carefully by acid reflux, resulting in differences in surface charge of MWCNTs without altering their physical properties. The surface condition of MWCNTs was also modified by adsorption of organic matter to compare bacterial toxicity of functionalized and non-functionalized MWCNTs in suspensions. Results show that although overall electrostatic repulsion and steric obstruction resulted from surface modifications led to elevated dispersivity of MWCNTs and mitigated toxicity on planktonic Escherichia coli cultures, no correlation between the dispersivity and bacterial toxicity of MWCNTs was observed, suggesting that dispersity alone may not be a proper index to estimate the CNT antibacterial effect on planktonic cells in the aqueous phase. In addition, viability recovery of MWCNT-treated cells was observed to be nutrition level-dependent, implying that availability of proper nutrients may be another important factor to be considered when assessing the ecotoxicity of CNTs in the aquatic system.

Smart Polymeric Hydrogels for Cartilage Tissue Engineering: A Review on the Chemistry and Biological Functions

Stimuli responsive hydrogels (SRHs) are attractive bioscaffolds for tissue engineering. The structural similarity of SRHs to the extracellular matrix (ECM) of many tissues offers great advantages for a minimally invasive tissue repair. Among various potential applications of SRHs, cartilage regeneration has attracted significant attention. The repair of cartilage damage is challenging in orthopedics owing to its low repair capacity. Recent advances include development of injectable hydrogels to minimize invasive surgery with nanostructured features and rapid stimuli-responsive characteristics. Nanostructured SRHs with more structural similarity to natural ECM up-regulate cell-material interactions for faster tissue repair and more controlled stimuli-response to environmental changes. This review highlights most recent advances in the development of nanostructured or smart hydrogels for cartilage tissue engineering. Different types of stimuli-responsive hydrogels are introduced and their fabrication processes through physicochemical procedures are reported. The applications and characteristics of natural and synthetic polymers used in SRHs are also reviewed with an outline on clinical considerations and challenges.

A case study of aggregation behaviors of titanium dioxide nanoparticles in the presence of dodecylbenzene sulfonate in natural water

The present work aims to ascertain the mechanisms of surfactant (dodecylbenzene sulfonate; DBS) effects on the aggregation behaviors of TiO2 nanoparticles (TiO2-NPs) in natural water samples. Aggregation experiments were conducted at a TiO2-NPs concentration of 10mg/L in deionized water and in natural water samples via dynamic light scattering and Zeta potential determination. Average attachment efficiency was calculated to compare the aggregation behaviors of nanoparticles in the two aqueous media. Results showed that the effects of DBS on aggregation could be interpreted by both Derjaguin-Landau-Verwey-Overbeek (DLVO) and non-DLVO mechanisms. In natural water samples, aggregation did not occur rapidly and was able to develop slowly under all conditions, and the roles of DBS were obvious at high DBS concentration owing to the impacts of inherent components of natural water samples, such as colloids and natural organic compounds. Future aggregation studies should concentrate on multi-factor, multi-colloidal and dynamic aspects under similar environmental conditions.

Extracellular bio-production and characterization of small monodispersed CdSe quantum dot nanocrystallites

Engineered nanoparticles of diverse forms are being profoundly used for various applications and demand ecologically benign synthesis processes. Conventional chemical methods employed for the syntheses of nanoparticles are environmentally unfriendly and energy intensive. Biologically inspired biofabrication approaches that utilize naturally existing microorganisms or plant extracts or biomaterials might overcome these issues. The present investigation for the first time shows the synthesis of small and monodispersed cadmium selenide nanoparticles utilizing the plant pathogenic fungus, Helminthosporum solani upon incubating with an aqueous solution of CdCl2 and SeCl4 under ambient conditions. Multiple physical characterizations involving ultraviolet-visible and photoluminescence spectroscopy, transmission electron microscopy, selected area electron diffraction and X-ray photoelectron spectroscopy confirmed the production, purity, optical and surface characteristics, crystalline nature, size and shape distributions, and elemental composition of the nanoparticles. Pluralities of the particles are monodisperse spheres with a mean diameter of 5.5±2 nm, are hydrophilic, highly stable with a broad photoluminescence and 1% quantum yield. This approach provides an alternative facile route for the biofabrication of quantum dot that is reliable, environmentally friendly, and lends itself directly for the creation of fluorescent biological labels.

Chemically cross-linked and grafted cyclodextrin hydrogels: from nanostructures to drug-eluting medical devices

The unique ability of cyclodextrins (CDs) to form inclusion complexes can be transmitted to polymeric networks in which CDs are chemically grafted or cross-linked. Combination of CDs and hydrogels in a single material leads to synergic properties: the hydrophilic network enhances biocompatibility and prevents dilution in the physiological medium increasing the stability of the inclusion complexes, while CDs finely tune the mechanical features and the stimuli-responsiveness and provide affinity-based regulation of drug loading and release. Therefore, CD-functionalized materials are opening new perspectives in pharmacotherapy, emerging as advanced delivery systems (DDS) for hydrophobic and hydrophilic drugs to be administered via almost any route. Medical devices (catheters, prosthesis, vascular grafts, bone implants) can also benefit from surface grafting or thermofixation of CDs. The present review focuses on the approaches tested to synthesize nano- to macro-size covalently cross-linked CD networks: i) direct cross-linking through condensation with di- or multifunctional reagents, ii) copolymerization of CD derivatives with acrylic/vinyl monomers, and iii) grafting of CDs to preformed medical devices. Examples of the advantages of having the CDs chemically bound among themselves and to substrates are provided and their applicability in therapeutics discussed.

Rapid, Low-Cost, and Ecofriendly Approach for Iron Nanoparticle Synthesis Using Aspergillus oryzae TFR9

Development of reliable and ecofriendly green approach for synthesis of metallic nanoparticles biologically is an important step in the field of application of nanoscience and nanotechnology. The present paper reports the green approach for iron nanoparticle synthesis using Aspergillus oryzae TFR9 using FeCl3 as a precursor metal salt. Valid characterization techniques employed for biosynthesized iron nanoparticles including dynamic light scattering (DLS), transmission electron microscopy (TEM), and high resolution-transmission electron microscopy (HR-TEM) for morphological study. X-ray energy dispersive spectroscopy (EDS) spectrum confirmed the presence of elemental iron signal in high percentage. Apart from ecofriendliness and easy availability, low-cost biomass production will be more advantageous when compared to other chemical methods. Biosynthesis of iron nanoparticles using fungus has greater commercial viability that it may be used in agriculture, biomedicals and engineering sector.

Relating nanomaterial properties and microbial toxicity

Metal and metal oxide nanoparticles are among the most commonly used nanomaterials and their potential for adversely affecting environmental systems raises concern. Complex microbial consortia underlie environmental processes, and the potential toxicity of nanoparticles to microbial systems, and the consequent impacts on trophic balances, is particularly worrisome. The diverse array of metal and metal oxides, the different sizes and shapes that can be prepared and the variety of possible surface coatings complicate assessments of toxicity. Further muddling biocidal interpretations are the diversity of microbes and their intrinsic tolerances to stresses. Here, we review a range of studies focused on nanoparticle-microbial interactions in an effort to correlate the physical-chemical properties of engineered metal and metal oxide nanoparticles to their biological response. General conclusions regarding the parent material of the nanoparticle and the nanoparticle's size and shape on potential toxicity can be made. However, the surface coating of the material, which can be altered significantly by environmental conditions, can ameliorate or promote microbial toxicity. Understanding nanoparticle transformations and how the nanoparticle surface can be designed to control toxicity represents a key area for further study. Additionally, the vast array of microbial species and the structuring of these species within communities complicate extrapolations of nanoparticle toxicity in real world settings. Ultimately, to interpret the effect and eventual fate of engineered materials in the environment, an understanding of the relationship between nanoparticle properties and responses at the molecular, cellular and community levels will be essential.

Fluorescence in nanobiotechnology: sophisticated fluorophores for novel applications

Nanobiotechnology is one of the fastest growing and broadest-ranged interdisciplinary subfields of the nanosciences. Countless hybrid bio-inorganic composites are currently being pursued for various uses, including sensors for medical and diagnostic applications, light- and energy-harvesting devices, along with multifunctional architectures for electronics and advanced drug-delivery. Although many disparate biological and nanoscale materials will ultimately be utilized as the functional building blocks to create these devices, a common element found among a large proportion is that they exert or interact with light. Clearly continuing development will rely heavily on incorporating many different types of fluorophores into these composite materials. This review covers the growing utility of different classes of fluorophores in nanobiotechnology, from both a photophysical and a chemical perspective. For each major structural or functional class of fluorescent probe, several representative applications are provided, and the necessary technological background for acquiring the desired nano-bioanalytical information are presented.

Cyclodextrin-based nanogels for pharmaceutical and biomedical applications

Hydrophilic nanogels combine the advantages of hydrogels with certain advantages that are inherent in their nanoscale size. Similar to macrogels, nanogels can contain and protect drugs and regulate their release by incorporating high-affinity functional groups, stimuli-responsive conformations and biodegradable bonds into the polymer network. Similar to nanoparticles, nanogels can easily be administered in liquid form for parenteral drug delivery. The nanoscale size of nanogels gives them a high specific surface area that is available for further bioconjugation of active targeting agents. Biodistribution and drug release can be modulated through size adjustments. The incorporation of hydrophilic cyclodextrin (CD) moieties into the polymeric network of the nanogels provides them with a drug loading and release mechanism that is based on the formation of inclusion complexes without decreasing the hydrophilicity of the network. The covalent attachment of CD molecules to the chemically crosslinked networks may enable the CDs to display fully their ability to form complexes, while simultaneously preventing drug release upon media dilution. The preparation, characterization and advantages for pharmaceutical and biomedical applications of CD-based nanogels are reviewed in this article.

Monodispersed biocompatible silver sulfide nanoparticles: facile extracellular biosynthesis using the γ-proteobacterium, Shewanella oneidensis

Interest in engineered metal and semiconductor nanocrystallites continues to grow due to their unique size- and shape-dependent optoelectronic, physicochemical and biological properties. Therefore identifying novel non-hazardous nanoparticle synthesis routes that address hydrophilicity, size and shape control and production costs has become a priority. In the present article we report for the first time on the efficient generation of extracellular silver sulfide (Ag₂S) nanoparticles by the metal-reducing bacterium Shewanella oneidensis. The particles are reasonably monodispersed and homogeneously shaped. They are produced under ambient temperatures and pressures at high yield, 85% theoretical maximum. UV-visible and Fourier transform infrared spectroscopy, dynamic light scattering, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy measurements confirmed the formation, optical and surface properties, purity and crystallinity of the synthesized particles. Further characterization revealed that the particles consist of spheres with a mean diameter of 9±3.5 nm, and are capped by a detachable protein/peptide surface coat. Toxicity assessments of these biogenic Ag₂S nanoparticles on Gram-negative (Escherichia coli and S. oneidensis) and Gram-positive (Bacillus subtilis) bacterial systems, as well as eukaryotic cell lines including mouse lung epithelial (C 10) and macrophage (RAW-264.7) cells, showed that the particles were non-inhibitory and non-cytotoxic to any of these systems. Our results provide a facile, eco-friendly and economical route for the fabrication of technologically important semiconducting Ag₂S nanoparticles. These particles are dispersible and biocompatible, thus providing excellent potential for use in optical imaging, electronic devices and solar cell applications.

Biofabrication of discrete spherical gold nanoparticles using the metal-reducing bacterium Shewanella oneidensis

Nanocrystallites have garnered substantial interest due to their various applications, including catalysis and medical research. Consequently important aspects of synthesis related to control of shape and size through economical and non-hazardous means are desirable. Highly efficient bioreduction-based fabrication approaches that utilize microbes and/or plant extracts are poised to meet these needs. Here we show that the γ-proteobacterium Shewanella oneidensis can reduce tetrachloroaurate (III) ions to produce discrete extracellular spherical gold nanocrystallites. The particles were homogeneously shaped with multiple size distributions and produced under ambient conditions at high yield, 88% theoretical maximum. Further characterization revealed that the particles consist of spheres in the size range of ∼2-50 nm, with an average size of 12±5 nm. The nanoparticles were hydrophilic and resisted aggregation even after several months. Based on our experiments, the particles are likely fabricated by the aid of reducing agents present in the bacterial cell membrane and are capped by a detachable protein/peptide coat. Ultraviolet-visible and Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectra and transmission electron microscopy measurements confirmed the formation, surface characteristics and crystalline nature of the nanoparticles. The antibacterial activity of these gold nanoparticles was assessed using Gram-negative (Escherichia coli and S. oneidensis) and Gram-positive (Bacillus subtilis) bacterial species. Toxicity assessments showed that the particles were neither toxic nor inhibitory to any of these bacteria.