Ag and Au Nanoparticles as Color Indicators for Monomer/Micelle-Nanoparticle Interactions.

Ag and Au nanoparticles (NPs) were used as color indicators to determine the monomer/micelle adsorption on the NP surface. A simple methodology based on the color change of Ag/Au NPs upon interacting with surface-active molecules was developed. A contrasting color change occurred when NPs interact with the monomer/micelle. This was demonstrated by monitoring the adsorption behavior of a series of Gemini surfactants. UV-visible measurements showed a large change in the intensity and wavelength of Ag/Au NP absorbance upon the surface adsorption of the monomer/micelle of Gemini surfactants. The mechanism of surface adsorption and molecular orientation on the solid-liquid interface of NPs was determined by performing the FT-IR and XPS measurements. Results demonstrated that sharp color changes from yellow to red for Ag NPs and red to purple for Au NPs happened when the Gemini surfactant monomer/micelle adsorbs on the NP surface. This colorimeter-based methodology highlighted the applicability of Ag/Au NPs in complex media where such NPs frequently encounter surface-active molecules.

Hemolytic Response of Iron Oxide Magnetic Nanoparticles at the Interface and in Bulk: Extraction of Blood Cells by Magnetic Nanoparticles.

Surface-active and water-soluble magnetic nanoparticles (NPs) were synthesized in the presence of a series of amphiphilic molecules of different functional groups to determine the hemolytic response and their ability to extract blood cells across the interface and aqueous bulk while maintaining minimum hemolysis. Amphiphilic molecules such as Gemini surfactants of strong hydrophobicity and low hydrophilic-lipophilic balance produced surface-active magnetic NPs, which were highly cytotoxic even when placed at the blood suspension (aqueous)-air interface. A similar behavior was shown by water-soluble magnetic NPs produced using monomeric ionic and nonionic surfactants and different amino acids. The NPs produced using mild biological surfactants and mono- and oligosaccharides of the same functional group proved to be excellent blood cell extractors with minimum hemolysis. α/ß-cyclodextrin and dextrose-stabilized magnetic NPs induced negligible hemolysis and extracted more than 50% of blood cells. The results showed that nontoxic magnetic NPs are excellent blood cell extractors from the blood suspension when tagged with amphiphilic molecules possessing good biocompatibility with cell membranes without inducing hemolysis. The work highlights the biological applicability of nontoxic magnetic NPs at biointerfaces and in blood suspensions.

Extraction of Bionanomaterials from the Aqueous Bulk by Using Surface Active and Water-Soluble Magnetic Nanoparticles.

Surface active and water-soluble magnetic nanoparticles (NPs) were used to demonstrate the extraction of bionanomaterials from the aqueous bulk. Au NPs conjugated with different water-insoluble and water-soluble proteins were used as model bionanomaterials. UV-visible studies, zeta potential, and microscopic analyses were performed to quantify the extraction. Sodium dodecyl sulfate and dimethylene bis(dodecyldimethylammonium bromide) (12-2-12) stabilized surface active magnetic NPs were fully capable of extracting Au NPs conjugated with predominantly hydrophobic proteins from the aqueous bulk when placed at the aqueous-air interface. However, they were poor in extracting Au NPs from the aqueous bulk which were coated with predominantly hydrophilic water-soluble protein. On the other hand, water-soluble dodecyldimethyl-3-ammonio-1-propanesulfonate stabilized magnetic NPs proved to be fully capable of extracting all kinds of Au NPs conjugated with either water-soluble or water-insoluble proteins. The results highlight the remarkable ability of magnetic NPs in the extraction of bionanomaterials when placed at either biointerfaces or in the aqueous bulk of biological systems.

Colloidal Stabilization of Sodium Dilauraminocystine for Selective Nanoparticle-Nanoparticle Interactions: Their Screening and Extraction by Iron Oxide Magnetic Nanoparticles.

Nanoparticle-nanoparticle (NP-NP) interactions between Au and Ag NPs were studied by using sodium dilauraminocystine (SDLC)- and Gemini surfactant-stabilized NPs to demonstrate the unique NP surface adsorption behavior of SDLC in controlling and mimicking such interactions in complex mixtures. They were significantly affected by the spacer as well as the polymeric nature of the head group of Gemini surfactants. A longer spacer impeded while a polymeric head group facilitated the interactions. The Au-Ag NPs interactions in an aqueous phase were also controlled by placing surface-active magnetic NPs at an aqueous-air interface, which interacted with either or both kinds of interacting NPs in an aqueous phase and reduced their ability to interact with each other. On the other hand, water-soluble zwitterionic magnetic NPs proved to be excellent extractants of both Au and Ag NPs from the aqueous phase. Extraction efficiency depended on the strength of interactions between the water-soluble magnetic NPs and aqueous-solubilized Au and/or Ag NPs.

Avoiding Hemolytic Anemia by Understanding the Effect of the Molecular Architecture of Gemini Surfactants on Hemolysis.

Hemolytic behavior of a series of different categories of Gemini surfactants was determined in their low concentration range. Cationic Gemini surfactants of different molecular architectures prove to be highly cytotoxic even at 0.1 mM. Anionic and amino acid-based Gemini surfactants were minimally cytotoxic, although their toxicity was concentration-dependent. With respect to monomeric surfactants of comparable hydrocarbon chain lengths, cationic Gemini surfactants were much more toxic than anionic Gemini surfactants. Incubation temperature was another important parameter that significantly drove the hemolysis irrespective of the molecular structure of the surfactant. Results indicated that the surface activity or liquid-blood cell membrane adsorption tendency of a surfactant molecule determined the degree of hemolytic anemia. Greater surface activity induced greater cytotoxicity, especially when the surfactant possessed a stronger ability to interact with the membrane proteins through hydrophilic interactions. That provided cationic Gemini surfactants a higher ability for hemolytic anemia because they were able to interact with an electronegative cell membrane with favorable interactions in comparison to anionic or amino acid-based Gemini surfactants. These findings are expected to help in designing surface-active drugs with a suitable molecular architecture that can avoid hemolytic anemia.

Mechanistic Aspects of Simultaneous Extraction of Silver and Gold Nanoparticles across Aqueous-Organic Interfaces by Surface Active Iron Oxide Nanoparticles.

Surface active iron oxide nanoparticles (NPs) were used for the simultaneous extraction of water soluble Ag and Au NPs across an aqueous-organic interface from aqueous bulk. The surface activity of iron oxide NPs was achieved by using cationic Gemini surfactants of different architectures during the in situ synthesis of iron oxide NPs in hydrothermal synthesis. Aqueous bulk solubility of Ag and Au NPs was achieved by stabilizing them with conventional surfactants of different polarities such as SDS, CTAB, and DDM. The amphiphilic nature of iron oxide NPs demonstrated their remarkable ability to extract Ag and Au NPs through both hydrophilic and hydrophobic interactions. The mechanism of extraction from aqueous bulk was monitored by placing different amounts of surface active iron oxide NPs on the aqueous-organic interface and was studied with the help of UV-visible, DLS, and IR measurements. XPS and TEM measurements were used for the quantitative estimation of efficiency of extraction. Extraction was facilitated when both hydrophilic and hydrophobic interactions were participating simultaneously. Results may help in designing a suitable method for purification of industrial effluents contaminated with metal particulates simply by applying an external magnetic field rather than going through a complicated conventional filtration process.

Photophysical behavior of heme group: Unfolding of hemoglobin and myoglobin in the presence of Gemini surfactants of different molecular architectures.

Fluorescence studies were performed to determine the photophysical behavior of heme group in the presence of cationic Gemini surfactants of different architectures. Both hemoglobin and myoglobin were used to understand the heme group interactions with Gemini surfactants under the influence of temperature variation and were compared with homologous monomeric surfactants. The results were also supplemented from the size and zeta potential measurements of both proteins. Gemini surfactants showed marked effect on the unfolding behavior of hemoglobin that mainly contributed by the stronger hydrophobic interactions of double hydrocarbon chains as well as methylene spacer in the head group region with the hydrophobic domains of hemoglobin. Myoglobin with single polypeptide chain did not show similar unfolding behavior in the presence of Gemini surfactants rather it was readily solubilized in the surfactant solution and that too in the presence of monomeric surfactants rather than Gemini surfactants. The results highlighted the mechanistic aspects by which water soluble globular proteins interact with amphiphilic molecules of different functionalities and thus, helped to predict the interactions of both hemoglobin and myoglobin with the complex biological molecules possessing similar functionalities.

Impact of nanomaterials on ecosystems: Mechanistic aspects in vivo.

Nanotechnologies are becoming increasingly popular in modern era of human development in every aspect of life. Their impact on our ecosystem in air, soil, and water is largely unknown because of the limited amount of information available, and hence, they require considerable attention. This account highlights the important routes of nanomaterials toxicity in air, soil, and water, their possible impact on the ecosystem and aquatic life. The mechanistic aspects have been focused on the size, shape, and surface modifications of nanomaterials. The preventive measures and future directions along with appropriate designs and implementation of nanotechnologies have been proposed so as to minimize the interactions of nanomaterials with terrestrial flora and aquatic life. Specifically, the focus largely remains on the toxicity of metallic nanoparticles such as gold (Au) and silver (Ag) because of their applications in diverse fields. The account lists some prominent mechanistic routes of nanotoxicity along with in vivo experimental results based on the fundamental understanding that how nanometallic surfaces interact with plant as well as animal biological systems. The appropriate modifications of the nanometallic surfaces with biocompatible molecules are considered to be the most effective preventive measures to reduce the nanotoxicity.

Applications of Molecular Structural Aspects of Gemini Surfactants in Reducing Nanoparticle-Nanoparticle Interactions.

Oppositely charged nanoparticle (NP)-nanoparticle (NP) interactions were studied by titrating sodium dodecyl sulfate (SDS) stabilized NPs with cetyltrimethylammonium bromide (CTAB) stabilized NPs at constant temperature with the help of UV-visible and dynamic light scattering measurements. CTAB stabilized NPs were systematically replaced with a series of cationic gemini surfactants to demonstrate the effect of head group and hydrocarbon tail modifications on the electrostatic interactions with SDS stabilized NPs. Introduction of the dimeric gemini head group (alkylammonium or imidazolium), spacer length, and double tail hydrocarbon length all significantly reduced the NP-NP interactions and delayed their salting-out process. They lead to the formation of stable colloidal aqueous solubilized NP-NP complexes. The results concluded that NP-NP interactions can be overcome if appropriately stabilized NPs are used to maintain their colloidal stability so as to achieve maximum applicability.

Role of Gluten in Surface Chemistry: Nanometallic Bioconjugation of Hard, Medium, and Soft Wheat Protein.

Hard, medium, and soft wheat proteins, based on gluten content, were studied for their important roles in nanometallic surface chemistry. In situ synthesis of Au nanoparticles (NPs) was followed to determine the surface adsorption behavior of wheat protein based on the gluten contents. A greater amount of gluten contents facilitated the nucleation to produce Au NPs. X-ray photoelectron spectroscopy (XPS) surface analysis clearly showed the surface adsorption of protein on nanometallic surfaces which was almost equally prevalent for the hard, medium, and soft wheat proteins. Wheat protein conjugated NPs were highly susceptible to phase transfer from aqueous to organic phase that was entirely related to the amount of gluten contents. The presence of higher gluten content in hard wheat protein readily enabled the hard wheat protein conjugated NPs to move across the aqueous-organic interface followed by medium and soft wheat protein conjugated NPs. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS page) analysis allowed us to determine molar masses of nanometallic surface adsorbed protein fractions. Only two protein fractions of high molar masses (74 and 85 kDa) from SDS solubilized hard, medium, and soft wheat proteins preferred to adsorb on nanometallic surfaces out of more than 15 protein fractions of pure wheat protein. This made the surface adsorption of wheat protein highly selective and closely related to gluten content. Cetyltrimethylammonium bromide (CTAB) solubilized wheat protein conjugated NPs demonstrated their strong antimicrobial activities against both Gram negative and Gram positive bacteria making them suitable for their applications in food industry.

Keto-Enol Tautomerism of Temperature and pH Sensitive Hydrated Curcumin Nanoparticles: Their Role as Nanoreactors and Compatibility with Blood Cells.

In order to provide a solution for the poor aqueous solubility and poor bioavailability of curcumin, we present the synthesis and characteristic features of water-soluble curcumin hydrated nanoparticles (CNPs). They are stable and nearly monodisperse in the aqueous phase where the keto form of curcumin self-assembles into spherical CNPs, which are highly sensitive to temperature and pH variations. The CNPs are quite stable up to 40 °C and at neutral pH. A higher temperature range reduces their hydration and makes them unstable, thereby disintegrating them into smaller aggregates. Similarly, a higher pH converts the keto form of CNPs into the enol form by promoting their interparticle fusions driven by hydrogen bonding with a remarkable color change from yellow to bright orange-red which demonstrates their excellent photophysical behavior. The stable keto form CNPs are highly efficient nonreactors for the in situ synthesis of Au, Ag, and Pd NPs which are simultaneously entrapped in curcumin aggregates, thus promoting the metal NP carrying ability of curcumin aggregates. The CNPs also demonstrate their excellent dose-dependent biocompatibility with blood cells. A concentration range up to 5 mM of CNPs is quite safe for their applications in biological systems.

Applications of rice protein in nanomaterials synthesis, nanocolloids of rice protein, and bioapplicability.

Rice protein conjugated nanomaterials were synthesized and characterized by using anionic and cationic forms of rice protein. Both forms showed unique characteristic features when used in in situ reaction conditions for synthesizing the protein stabilized gold (Au) and silver (Ag) nanoparticles (NPs). Au NPs synthesis was highly facilitated than Ag NPs synthesis while the reverse was true when rice protein was simply used in the basic medium. Photophysical behavior clearly showed the contributions of both electrostatic and non-electrostatic interactions driving the rice protein surface adsorption on nanometallic surfaces. Rice protein conjugated NPs were easily transferred and extracted into the organic phase while the extraction process was related to the amount of protein coating. Under the controlled pH reaction conditions, rice protein - dye colored NPs were synthesized which were further characterized by the DLS and SDS Page analysis. Both rice protein conjugated Au/Ag NPs and rice protein NPs showed remarkable biocompatibility with blood cells. These NPs demonstrated their excellent ability to selectively extract protein fractions from complex biological fluid like serum. The results proposed significant applications of rice protein conjugated NPs in biological systems as well as bio-nanotechnology.

Engineered nanomaterials growth control by monomers and micelles: From surfactants to surface active polymers.

In pseudo-micellar phase, the crystal growth is primarily achieved by the surface activity of the monomers in the presence of micelles. To ensure the maximum potential of surface activity of monomers in morphology control, a micellar phase is required. This account specifically focuses on the crystal growth control by the surface active monomers of conventional surfactants and that of water soluble polymers. It also distinguishes the mechanisms involved in the shape control driven by the micellar phase of micelle forming polymers, their role as nanoreactors, micellar stability, and micellar transitions from the monomeric phase. The fundamental basis of the crystal growth control by the surface active agents holds the key of using other non-convectional surface active species like proteins, carbohydrates, and bioactive polymers to achieve morphology control bionanomaterials for their specific biological applications.

Naringin-Chalcone Bioflavonoid-Protected Nanocolloids: Mode of Flavonoid Adsorption, a Determinant for Protein Extraction.

In order to highlight the applications of bioflavonoids in materials chemistry, naringin and its chalcone form were used in the nanomaterial synthesis to produce flavonoid-conjugated nanomaterials in aqueous phase. Chalcone form proved to be excellent reducing as well as stabilizing agent in the synthesis of monodisperse Au, Ag, and Pd nanoparticles (NPs) of ∼5-15 nm, following in situ reaction conditions where no external reducing or stabilizing agents were used. The mechanism of NP surface adsorption of flavonoid was determined with the help of dynamic light scattering and zeta potential measurements. Surface-adsorbed flavonoids also allowed NPs to easily transfer into the organic phase by using aqueous insoluble ionic liquid. Pd NPs attracted the excessive amount of surface adsorption of both naringin as well as its chalcone form that in turn drove Pd NPs in self-assembled state in comparison to Au or Ag NPs. An amount of surface-adsorbed flavonoids selectively determined the extraction of protein fractions from complex zein corn starch protein solution. Self-assembled Pd NPs with a large amount of surface-adsorbed naringin preferentially extracted zein fraction of higher molar mass, whereas Au and Ag NPs almost equally extracted the zein fractions of lower molar masses.

Ag Nanometallic Surfaces for Self-Assembled Ordered Morphologies of Zein.

Nanometallic surfaces of Ag nanoparticles (NPs) catalyzed the self-aggregation behavior of zein in different ordered morphologies such as cubes, rectangles, and bars. This was studied in a ternary in situ reaction (AgNO3 + zein + water), where zein performed the reduction as well as stabilization of Ag NPs. This reaction produced small Ag NPs of less than 10 nm predominantly bound with {111} crystal planes, which attracted the surface adsorption of zein. Surface-adsorbed zein initiated the protein seeding and converted the tertiary structure of protein into open ß-pleated structure with aqueous exposed hydrophobic domains. A layered deposition of ß-pleats on different crystal planes of Ag NPs derived them to nearly monodispersed cubic morphologies. The mechanistic aspects of self-aggregation of zein in the presence of nanometallic surfaces hold possible scenarios for simple and straightforward routes of protein crystallization.

Nanotoxicity in Systemic Circulation and Wound Healing.

Nanotoxicity of nanomaterials is an important issue in view of their potential applications in systemic circulation and wound healing dressing. This account specifically deals with several characteristic features of different nanomaterials which induce hemolysis and how to make them hemocompatible. The shape, size, and surface functionalities of naked metallic as well as nonmetallic nanoparticles surfaces are responsible for the hemolysis. An appropriate coating of biocompatible molecules dramatically reduces hemolysis and promotes their ability as safe drug delivery vehicles. The use of coated nanomaterials in wound healing dressing opens several new strategies for rapid wound healing processes. Properly designed nanomaterials should be selected to minimize the nanotoxicity in the wound healing process. Future directions need new synthetic methods for engineered nanomaterials for their best use in nanomedicine and nanobiotechnology.

Nanoparticle Surface Specific Adsorption of Zein and Its Self-assembled Behavior of Nanocubes Formation in Relation to On-Off SERS: Understanding Morphology Control of Protein Aggregates.

Zein, an industrially important protein, is characterized in terms of its food and pharmaceutical coating applications by using surface enhanced Raman spectroscopy (SERS) on Au, Ag, and PbS nanoparticles (NPs). Its specific surface adsorption behavior on Ag NPs produced self-assembled zein nanocubes which demonstrated on and off SERS activity. Both SERS characterization as well as nanocube formation of zein helped us to understand the complex protein aggregation behavior in shape controlled morphologies, a process with significant ramifications in protein crystallization to achieve ordered morphologies. Interestingly, nanocube formation was promoted in the presence of Ag rather than Au or PbS NPs under in situ synthesis and discussed in terms of specific adsorption. Zein fingerprinting was much more clear and enhanced on Au surface in comparison to Ag while PbS did not demonstrate SERS due to its semiconducting nature.

Colloidal micelles of block copolymers as nanoreactors, templates for gold nanoparticles, and vehicles for biomedical applications.

Target drug delivery methodology is becoming increasingly important to overcome the shortcomings of conventional drug delivery absorption method. It improves the action time with uniform distribution and poses minimum side effects, but is usually difficult to design to achieve the desire results. Economically favorable, environment friendly, multifunctional, and easy to design, hybrid nanomaterials have demonstrated their enormous potential as target drug delivery vehicles. A combination of both micelles and nanoparticles makes them fine target delivery vehicles in a variety of biological applications where precision is primarily required to achieve the desired results as in the case of cytotoxicity of cancer cells, chemotherapy, and computed tomography guided radiation therapy.

Protein mixtures of environmentally friendly zein to understand protein-protein interactions through biomaterials synthesis, hemolysis, and their antimicrobial activities.

Industrially important zein protein has been employed to understand its interactions with two model proteins bovine serum albumin (BSA) and cytochrome c (Cyc,c) following the in vitro synthesis of Au NPs so as to expand its applicability for biological applications. Interactions were studied under the effect of temperature variation by UV-visible and fluorescence emission studies. Temperature induced unfolding in the protein mixtures indicated their degree of mutual interactions through simultaneous nucleation of gold nanoparticles (Au NPs) and their subsequent shape control effects. Zein + BSA mixtures showed favorable protein-protein interactions over the entire mole fraction range with maximum close to x(BSA) = 0.24, whereas zein + Cyc,c showed such interactions only in the zein rich region with significant demixing in the Cyc,c rich region of the mixtures. Both hydrophobic as well as hydrophilic domains in the unfolded states were driving such interactions in the case of zein + BSA mixtures while demixing was the result of the predominant hydrophilic nature of Cyc,c and its self-aggregation behavior in the Cyc,c rich region in contrast to the predominant hydrophobic nature of zein. Zein + BSA mixtures produced small roughly spherical Au NPs fully coated with protein, whereas the demixing zone of zein + Cyc,c mixtures generated highly anisotropic NPs with little protein coating. To explore their biological applications, protein conjugated NPs of both mixtures were subjected to hemolysis where NPs coated with the former mixture showed little hemolysis and may act as drug delivery vehicles in systemic circulation in comparison to the latter. Both kinds of NPs further demonstrated their extraordinary antimicrobial activities with different kinds of strains and proved to be highly important environmentally friendly biomaterials.

pH and thermo-responsive tetronic micelles for the synthesis of gold nanoparticles: effect of physiochemical aspects of tetronics.

Micelles of the star shaped block polymers "tetronics" were employed for the synthesis of gold (Au) nanoparticles (NPs) under the effect of pH and temperature variation. The presence of the diamine core in the tetronic macromolecule made its micelles highly pH responsive, thereby dramatically altering the physiochemical properties. Likewise, a high degree of hydration made the micelles temperature sensitive. UV-visible studies, transmission electron microscopy (TEM), gel electrophoresis, and structure optimization by energy minimization were applied to understand the physiochemical aspects of tetronic micelles and their further role in the synthesis of Au NPs. Synthesis of Au NPs was triggered by the surface cavities of the micelles and hence the NPs simultaneously adsorbed on the micelle surface. Low pH induced high hydration and temperature responsive well defined vesicular morphologies bearing Au NPs, while high pH produced mainly large and compact compound micelles carrying NPs. Both pH and temperature responsive behaviors of different tetronics significantly influenced the synthesis of Au NPs and thus demonstrated their ability to act as nanoreactors for the materials synthesis under different experimental conditions.