Anuj Tripathi

Uranium (VI) recovery from aqueous medium using novel floating macroporous alginate-agarose-magnetite cryobeads

This study presents a novel development of a floating polymeric-magnetite cryobead for the recovery of hexavalent uranium from the aqueous sub-surfaces. The alginate-agarose-magnetite cryobeads were synthesized by the process of cryotropic-gelation at subzero-temperature. The physico-chemical properties of cryobeads showed high surface area and high interconnected porosity (≈ 90%). Low density of these cryobeads explains their floating property in the aqueous medium. The rheological analysis of cryobeads showed its stability and increased stiffness after uranium adsorption. The presence of magnetite nanoparticles in the porous cryobeads facilitates the recovery of these beads by applying an external magnetic field. Maximum uranium adsorption (97 ± 2%) was observed in the pH range of 4.5-5.5. The thermodynamic parameters suggest passive endothermic adsorption behaviour. HCl was found to be an efficient eluent for the uranium desorption. Five repeated cycles for the desorption of uranium from biosorbent showed 69 ± 3% of uranium recovery. These results suggest stability of these novel floating magnetite-cryobeads under environmental conditions with potential for the recovery of uranium from contaminated aqueous subsurfaces.

Preparation of a sponge-like biocomposite agarose–chitosan scaffold with primary hepatocytes for establishing an in vitro 3D liver tissue model

Designing a three-dimensional (3D) macroporous scaffold with desired bio-functional properties is an important aspect for fabricating an in vitro liver tissue model with applications in pre-clinical therapeutics testing. In the present study a bio-polymeric composite scaffold of agarose–chitosan (AG–CH) was synthesized at optimized sub-zero temperature and evaluated for its suitability in in vitro liver tissue engineering. The scaffold showed high porosity (83 ± 2%) with interconnected pores (average pore diameter 40–70 μm). High swelling kinetics on account of the hydrophilic pore channels in the AG–CH scaffold allows unhindered migration of cells and gaseous exchange. At neutral pH, the negative charge on the surface of the AG–CH scaffold ensures increased cell-to-cell interfacial interaction followed by colonization of hepatocytes. Rheological studies of the hydrated scaffold demonstrate its high sponge-like visco-elastic behavior without any fracture deformation up to 34 ± 1 N, which insinuates its applicability for soft-tissue engineering. The AG–CH scaffold showed ∼15% degradation in a span of four weeks in sterile PBS at physiological pH, which could help to maintain the structural integrity of neo-tissue formation. In vitro primary hepatocytes proliferation in the AG–CH scaffold showed an increase in cellular metabolic activity. The hepatic functions like albumin secretion and urea synthesis were established for the primary hepatocytes in the 3D scaffold and were higher in comparison to the control. The expression of hepatic CYP450 biomarker was observed in the in vitro cultured hepatocytes immobilized in the 3D AG–CH scaffold. Thus, the AG–CH scaffold with suitable physico-chemical properties and hepatic cell compatibility present its potential for developing an in vitro liver tissue model.

Polymeric macroporous formulations for the control release of mosquitocidal Bacillus sphaericus ISPC-8

Bio-polymeric mosquitocidal formulations were developed for the control release of Bacillus sphaericus ISPC-8 by the immobilization of its spore-crystal complex onto the macroporous polymeric matrices. The biodegradable formulations were synthesized at sub-zero temperature using natural polymeric substrates like agarose, alginate, cellulose, non-adsorbent cotton, wooden cork powder and also magnetite nanoparticles. The obtained polymeric matrices were morphologically characterized, which showed 85-90% porosity, uniform pores distribution, high permeability and controlled degradation (19-30%) in 4 weeks depending upon the composition of formulations. Further, the polymeric macroporous formulations were tested for persistence of mosquitocidal activity against Culex quinquefasciatus larvae. Unformulated B. sphaericus ISPC-8 spores retained 54% of larvicidal activity after 7 days, which completely reduced after 35 days of treatment. However, the immobilized B. sphaericus spores in agarose-alginate formulations showed high larvicidal activity on day 7 and retained about 45% activity even after 35 days of treatments. Studies on UV-B and pH dependent inactivation of toxins and spore viability showed that these formulations were significantly protecting the spores as compared to the unformulated spores, which suggest its potential application for the mosquito control program.

Correlation of Mo dopant and photocatalytic properties of Mo incorporated TiO2: an EXAFS and photocatalytic study

The present study addresses the quantitative estimation and understanding of the nature of phases present in Mo-incorporated titania through extensive EXAFS measurements (at Mo K-edge and Ti K-edge) and to decipher their role in photodegradation of Methylene Blue (MB) dye under UV and visible irradiation. EXAFS results revealed the presence of both MoO3 nano heterophase phase and substitutional Mo dopants in the TiO2 lattice, the extent of the latter was reduced with the increasing Mo content of the sample. The presence of MoO3 in the Mo-incorporated titania was also revealed by FT-IR and TEM studies. Photocatalytic studies have shown considerable adsorption of the cationic MB-dye, perhaps due to the electronic interaction between the dye and catalytic surface. Under visible irradiation, the photocatalytic activity followed the trend: Mo-5 > Mo-2 > Mo-1 > Mo-10 ≫ TiO2, while the trend for photodegradation of MB dye under UV irradiation was as follows: Mo-5 > Mo-2 > Mo-1 > TiO2 > Mo-10. These results have been explained in the light of the structural properties of the Mo–TiO2 system obtained from EXAFS measurements. It has been observed that the relative ratio of substitutional Mo-dopant to the MoO3 phase in this tri-phasic photocatalyst plays a crucial role in augmenting its oxidative photocatalytic property.

Plasma Surface Modification of Biomaterials for Biomedical Applications

Application oriented selection of a material depends on the bulk properties of that material. However, a first encountering feature of any material in an application is its surface and thus material’s surface is one of the foremost parameter that decides the fate of material performance. Modulating the surface properties is considered as a potential approach to meet the application requirement. In past, various techniques (like, chemical, γ-irradiation, mechanical abrasion) have been developed for the surface modification of materials. These methods have certain disadvantages, like chemical treatment involve the disposal of polluted solvents/water in the environment, whereas other techniques may affect bulk properties of the material. Since three decades, plasma surface modification technique has attracted attention of scientists and technologists for creating new surfaces for various end-use applications such as textiles, food packaging, coatings, medical devices etc. Especially, low temperature plasma (low pressure and atmospheric pressure glow discharge) has attracted for its potential application in the new biomedical devices and biomaterials development. Plasma processing has proved itself a very promising and potent technology for modification of surface properties in an effective, environment friendly and economical way for converting low cost materials into a value added materials. The surface properties and biocompatibility can be enhanced selectively and precisely without affecting material’s bulk properties by the use of plasma surface modification technique. This chapter is providing a brief overview of low temperature plasma as a versatile technology for surface modification and its application pertaining to biomedical materials research. Various inferences are also drawn from the types of plasma used in the biomedical applications.

On-column enzymatic synthesis of melanin nanoparticles using cryogenic poly(AAM-co-AGE) monolith and its free radical scavenging and electro-catalytic properties

In the present study we have demonstrated a green-route for the synthesis of melanin nanoparticles (Mel-NPs). To achieve this, a monolith column of poly(acrylamide-co-allylglycidyl ether) was synthesized and further modified to immobilize the enzyme tyrosinase, which was extracted from the corm of plant tuber Amorphophallus campanulatus. The immobilization of the enzyme was carried out in two steps. First, the epoxy groups present on the monolith surface were coupled with ethylene diamine followed by glutaraldehyde to introduce aldehyde moieties. In the second step, aldehyde functionalized monolith column was treated with enzyme solution for covalent bonding through Schiffs base formation. The physico-chemical characterization of monolith, exhibited ideal column characteristics like interconnected pore architecture, high flow rate, hydrophilicity and amiable mechanical strength. The convective flow of L-3,4-dihydroxyphenylalanine through the column brought about its conversion to Mel-NPs by biocatalytic activity of the immobilized enzyme. The spectral changes of the solution recorded in UV-visible region at regular time intervals showed that the synthesis of Mel-NPs occurred via formation of different intermediates. The size of the spherical Mel-NPs was in the range of 20 to 30 nm and its colloidal stability at different pH values was confirmed by measuring the zeta potential after a period of 8 weeks. FT-IR and TG analysis indicated that the bio-synthesized Mel-NPs showed characteristics similar to that of natural melanin. The IC50 value for free-radical scavenging activity of Mel-NPs was calculated to be 24 μg mL−1 using DPPH assay. Ferric-reducing action of Mel-NPs showed a concentration dependent increase under experimental conditions. Further, electro-catalytic activity of the glassy carbon electrode (GCE) modified with Mel-NPs was evaluated and was found to show a 2.4 fold enhancement in electro-chemical signal when compared with bare electrode. In conclusion, Mel-NPs synthesized by this novel approach can find applications in the development of antioxidant formulations, biosensor and other areas of interest.

Antimicrobial Surface Modification of Polymeric Biomaterials

Since the last century, polymeric materials have been playing an imperative role in the economy of modern world and have become an essential element in everydays life. Depending on their inherited properties and compositions, polymers can be used in a number of applications, which includes biomedical (e.g., prostheses, stent, drug delivery carrier, tissue engineering scaffold), food packaging, adhesives, cosmetic industries, textile industries, and in hygiene products. However, pathogenesis of microbial contamination is the most common and serious concern in polymeric biomaterials, which can not only alter the physical, chemical, thermal, mechanical, and degradation properties of material but can also cause acute health risk in most of their biomedical applications. The only way to utilize them effectively is to alter their properties by surface modification techniques. In this chapter, an extensive overview on the surface modification methods has been discussed to develop antimicrobial polymeric biomaterials.

Advances in Biomaterials for Biomedical Applications

Polymer blends and nanocomposites are widely explored for different biomedical applications such as biodegradable scaffolds, biosensors, implants and controlled drug release. Both, synthetic and semi-synthetic polymers are used in medical applications and have their inherent advantages and disadvantages. Synthetic polymers offer flexibility of varying monomer unit, molecular weight, branching and thus offer a diverse set of physico-mechanical properties, whereas natural polymers offer superior biocompatibility and biodegradation profile. Availability of polymer blending techniques adds another dimension to the property set that polymers can offer, and therefore polymer blending is often used to tailor biodegradability and physico-mechanical properties. Polymers, in general, have poor mechanical properties when compared to metals and ceramics, putting a load bearing limit on polymer-based medical implants. The addition of reinforcing/ functional filler is expected to overcome such disadvantages of polymers. Polymers composites are heterogeneous systems wherein polymers are compounded with micron or nano-size particles to render high strength, electrical conductivity or any other functional attribute. This chapter describes the technological aspects of polymer blends and nanocomposites with a specific reference to synthesis, characteristics and applications of multi-phasic polymer systems as implants, scaffolds, and controlled drug release matrices. A detailed account of synthetic and natural polymer nanocomposites along with a brief discussion on important nano-fillers used in medical applications and interface modification techniques is presented. Few examples of recently explored novel polymer blends and composites that displayed promising properties as implants, scaffolds, biosensors and control release matrices have also been discussed.

Synthesis of a low-density biopolymeric chitosan–agarose cryomatrix and its surface functionalization with bio-transformed melanin for the enhanced recovery of uranium(VI) from aqueous subsurfaces

This study presents the development of a biopolymeric cryomatrix for the recovery of uranium from aqueous subsurfaces. The agarose–chitosan (AC) cryomatrix was synthesized by the process of cryotropic-polymerization at −20 °C. The surface of the AC cryomatrix was further modified by green-chemistry using sequential conversion of L-Dopa to melanin through the biocatalytic activity of tyrosinase that was extracted from the corm of plant tuber Amorphophallus campanulatus. Functionalization of the AC cryomatrix with melanin (MAC cryomatrix) presented enhanced uranium uptake, resistance to degradation along with high thermal and mechanical stability. This cryomatrix showed high interconnected porosity (∼90%), high swelling kinetics and permeability. The optimized ratio of biopolymers and cryogenic parameters led to formation of a buoyant low-density matrix that is favorable for radionuclide recovery from subsurface of contaminated water. Maximum uranium adsorption of the melanin-functionalized agarose–chitosan (MAC) cryomatrix was 97% ± 2% observed at pH 5.5 and the qmax was 435 mg g−1. The thermodynamic parameters suggest passive endothermic adsorption behavior. Furthermore, changes in the rheological properties after uranium binding were studied by micro-rheometry. The binding of uranium and chemical attraction in these cryomatrices was confirmed by FTIR. HCl was found to be an efficient eluent for uranium desorption (92 ± 4%) from the MAC cryomatrix. Five repeated cycles of adsorption–desorption showed the reusability of the MAC cryomatrix. These results suggest stability of the low-density MAC cryomatrix under environmental conditions with the potential for recovery of uranium from contaminated aqueous subsurfaces, including seawater.

Magnetic Nanoparticles: Functionalization and Manufacturing of Pluripotent Stem Cells

Regenerative medicine uses cell alone or in combination with carrier to deliver at the required site for restoring the normal functions of diseased or degenerated tissue. Various strategies to restore tissue functions involve specific cell types, scaffolds and delivery processes that are still in developmental stage. Obtaining sufficient quantity of cells by non-invasive approach for the application in regenerative medicine is still a challenge. Pluripotent stem cells (PSCs), including embryonic stem cells and induced pluripotent stem cells (iPSCs), possess the inherent ability of self-renewal and differentiation into many cell types. In particular, iPSCs are of a special interest because patient-derived iPSCs have the ability to reproduce patient-specific clinical conditions. The development of manufacturing systems for PSCs, including cell culture engineering, is a challenging research field for the clinical application of PSCs such as in regenerative medicine. One of these manufacturing systems uses magnetic nanoparticles which are well known for their application in magnetic resonance imaging and magnetic hyperthermia. Besides, this chapter is focused on the basics of magnetic nanoparticles, its functionalization and further applications of a magnetic force-based cell manufacturing system for pluripotent stem cells. Indeed, we have developed a procedure in which cells are labeled with magnetite cationic liposomes via electrostatic interaction between the positively charged liposomes and the target cells. The culture system may provide a useful tool for studying the behavior of PSCs and an efficient way of PSCs manufacturing for clinical applications.