Biomimetic Methods Research Articles

Synthesis of Mitomycin C and Decarbamoylmitomycin C N2 deoxyguanosine-adducts

Mitomycin C (MC) and Decarbamoylmitomycin C (DMC) – a derivative of MC lacking the carbamate on C10 – are DNA alkylating agents. Their cytotoxicity is attributed to their ability to generate DNA monoadducts as well as intrastrand and interstrand cross-links (ICLs). The major monoadducts generated by MC and DMC in tumor cells have opposite stereochemistry at carbon one of the guanine–mitosene bond: trans (or alpha) for MC and cis (or beta) for DMC. We hypothesize that local disruptions of DNA structure from trans or cis adducts are responsible for the different biochemical responses produced by MC and DMC. Access to DNA substrates bearing cis and trans MC/DMC lesions is essential to verify this hypothesis. Synthetic oligonucleotides bearing trans lesions can be obtained by bio-mimetic methods. However, this approach does not yield cis adducts. This report presents the first chemical synthesis of a cis mitosene DNA adduct. We also examined the stereopreference exhibited by the two drugs at the mononucleotide level by analyzing the formation of cis and trans adducts in the reaction of deoxyguanosine with MC or DMC using a variety of activation conditions. In addition, we performed Density Functional Theory calculations to evaluate the energies of these reactions. Direct alkylation under autocatalytic or bifunctional conditions yielded preferentially alpha adducts with both MC and DMC. DFT calculations showed that under bifunctional activation, the thermodynamically favored adducts are alpha, trans, for MC and beta, cis, for DMC. This suggests that the duplex DNA structure may stabilize/oriente the activated pro-drugs so that, with DMC, formation of the thermodynamically favored beta products are possible in a cellular environment.

New Generation of Hydroxyapatite Bone Grafts from �Coral like� Synthetic Inorganic Precursors

Event Abstract Back to Event New Generation of Hydroxyapatite Bone Grafts from ‘Coral like’ Synthetic Inorganic Precursors Nimmy Mohan1 and Harikrishna P. Varma1 1 Sree Chitra Tirunal Institute for Medical Sciences and Technology, Bioceramics Laboratory, India Introduction: Hydroxyapatite being the inorganic component of bone tissue is the most studied biomaterial for use as bone grafts, scaffolds, fillers, cements, coatings etc for the repair and regeneration of bone defects [1]. Synthetic bone grafts overcome the problems of donor site morbidity and immune rejections. In the present scenario bone grafting is not only the replacement or regeneration of diseased or damaged tissue, but also the stimulatation of the process of bone remodelling by generating surface active moieties or cell signalling process possibly based on self-assembling, biomimetic, or nanofabrication methods [2]. Designing of bone grafts and scaffolds with the required interconnected porosity and adequate strength is a prerequisite for a tissue engineering scaffold. This helps in favouring osteogenesis, vascularisation, proper oxygenation and leads towards ossification [3],[4]. In the present study hydroxyapatite bone grafts/substitutes were synthesized from synthetic inorganic calcite and aragonite precursors via hydrothermal routes which involve the growth of exotic and unique crystal clusters with a preferred orientation in c-axis mimicking biological apatites under ambient conditions. Materials and Methods: Porous precursors of calcium carbonate were made in different forms such as beads, blocks and pellets to form natural ‘coral like’ materials by using a setting solution of sodium hydroxide and phosphoric acid maintaining the pH around 4. These preforms were then hydrothermally converted to hydroxyapatite by exchange reactions in various phosphate solutions controlling the kinetic and thermodynamic parameters, retaining the strength and stability of the material. In vitro bioactivity was evaluated by cell adhesion and proliferation studies on the material for 14 days. Results and Discussion: Phase identification by X-Ray Diffraction (XRD) shows that the initial precursor composition consists of calcite or aragonite phases. Further on hydrothermal conversion, progressive growth of the apatite phase was observed with time (1, 6, 12 hours). Microstructural analysis by Environmental Scanning Electron Microscopy (ESEM) shows that the newly developed material composed of clusters of apatitic crystals in plate like morphology with nacre like microstructure having porosities in the range of 20-500 microns. FTIR studies confirmed that the apatite is carbonated in nature. Excellent cell growth was observed in the material during 14 days of study which was analysed by cell titer blue assay. Fig: 1 XRD pattern showing the conversion of Calcium carbonate (calcite) precursor to hydroxyapatite phase Fig: 2 Microstructure of the scaffolds before (A) and after the exchange reactions (B-1h, C-6h, D-12 h) Fig: 3 Cell proliferation study using cell titer blue assay. Conclusion: Synthetic bioceramics are having low resorption properties mainly due to high temperature sintering processes used. Avoiding the high temperature sintering will improve the resorption property of the material by restricting the grain growth and thereby improving the dissolution of the material. Heavy metal contamination and low availability in harvesting environmentally concerned natural corals limits its usage as a precursor material. This study paves a novel method towards the development of new generation bioceramic scaffolds having adequate strength, large size, resorption and remodelling characteristics. The developed materials can be used for augmentation and reconstruction of dental and bone defects. Director, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India

Ethionamide biomimetic activation and an unprecedented mechanism for its conversion into active and non-active metabolites.

Ethionamide (ETH), a second-line anti-tubercular drug that is regaining a lot of interest due to the increasing cases of drug-resistant tuberculosis, is a pro-drug that requires an enzymatic activation step to become active and to exert its therapeutic effect. The enzyme responsible for ETH bioactivation in Mycobacterium tuberculosis is a monooxygenase (EthA) that uses flavin adenine dinucleotide (FAD) as a cofactor and is NADPH- and O2-dependant to exert its catalytic activity. In this work, we investigated the activation of ETH by various oxygen-donor oxidants and the first biomimetic ETH activation methods were developed (KHSO5, H2O2, and m-CPBA). These simple oxidative systems, in the presence of ETH and NAD+, allowed the production of short-lived radical species and the first non-enzymatic formation of active and non-active ETH metabolites. The intermediates and the final compounds of the activation pathway were well characterized. Based on these results, we postulated a consistent mechanism for ETH activation, not involving sulfinic acid as a precursor of the iminoyl radical, as proposed so far, but putting forward a novel reactivity for the S-oxide ethionamide intermediate. We proposed that ETH is first oxidized into S-oxide ethionamide, which then behaves as a "ketene-like" compound via a formal [2 + 2] cycloaddition reaction with peroxide to give a dioxetane intermediate. This unstable 4-membered intermediate in equilibrium with its open tautomeric form decomposes through different pathways, which would explain the formation of the iminoyl radical and also that of different metabolites observed for ETH oxidation, including the ETH-NAD active adduct. The elucidation of this unprecedented ETH activation mechanism was supported by the application of isotopic labelling experiments.

Adaptive Environmental Interfaces: Biomimetic Morphologies and Tactical Urbanism

Human social needs, once facilitated by cities are now satisfied through the internet of everything (IoE) and the internet of me (IoMe). Historically, centralized power structures have shaped urban environments to support human interaction. These interactions are now also satisfied through the distributed power structures of the internet; undermining the built environment. Forces of sustainability combined with the grafting of technology onto bodies and buildings are re-shaping urban development – catalyzing the emergence of new urban morphologies. Here stochastic and biomimetic research methods and modeling generate new morphological urban forms. Opportunities are revealed through IoE sensory information and infrastructural systems’ analysis.

Metal-Organic Frameworks/Graphene Oxide Composite: A New Enzymatic Immobilization Carrier for Hydrogen Peroxide Biosensors

Enzymatic loss and inactivation are two main problems that can degrade the performance of biosensor. In order to resolve the problems, a new enzymatic immobilization carrier was developed by using biomimetic methods. Horseradish peroxidase (HRP) was initially encapsulated into zeolitic imidazolate frameworks (ZIFs) severed as protective structure. To overcome electron transfer barrier of ZIFs, graphene oxide (GO) of high conductive graphene precursor was used to enhance their conductivity. Subsequently, ZIFs@HRP/GO and GO-polyethyleneimine with opposite charges were alternatively assembled onto the substrate of indium tin oxide to construct multilayer films of the biosensor. Systematic characterizations showed that ZIF-8 with an average size of approximately 160.9 nm encapsulating HRP uniformly grew onto the surface of GO. The newly designed structure combined with the excellent properties of the GO and ZIFs guarantee easy, direct electrochemistry and good catalytic activity toward H2O2 oxidation can be achieved with this biosensor. Electrochemical experiment study indicate that the resulting biosensor presented a wide linear range of 0.02–6 mmol/L, a low detection limit of 3.4 μmol /L (S/N = 3), excellent anti-interference ability, and long-term stability as well.

1,9-seco-Bicyclic Polyprenylated Acylphloroglucinols from Hypericum uralum.

Hyperuralones C-H (1-6), six new 1,9-seco-bicyclic polyprenylated acylphloroglucinols (1,9-seco-BPAPs) derived from the normal polyprenylated acylphloroglucinols with a bicyclo[3.3.1]nonane-2,4,9-trione core, together with six known analogues, were isolated from the aerial parts of Hypericum uralum. The structures of 1-6 were elucidated on the basis of the interpretation of NMR and MS spectroscopic data. The structure of attenuatumione B, a known compound isolated from H. attenuatum, was revised to that of a 1,9-seco-BPAP by NMR spectroscopic analysis and previous biomimetic synthesis methods. The inhibitory activities of these isolates on acetylcholinesterase were tested, and compounds 1 and 2 exhibited moderate activities with IC50 values of 9.6 and 7.1 μM, respectively.

Spider Silk and Bioinspired Silk on Wettability

We review recent research on nanostructure and biological physical structure models of spider silk. We introduce the biomimetic methods and bioinspired technology about how to fabricate the silk. We also impose great importance on wettability of natural and artificial spider silk according to recent development and potential functions in new promising fields. Keywords: Bioinspired materials, micro- and nanostructure, orb-weaving spiders, silk bio-mimicry, spider silk, wettability.

Dry sanitation concepts with inspiration from nature

Poor sanitation is a major problem for health and water resources in many developing countries. Inexpensive but also attractive toilets could be a way to fight these problems. However, radical new ideas are needed to identify innovative solutions. Such novel ideas might be found by using systematic design methods that search nature for animals and plants that solve similar problems. The paper describes how four conceptual sanitation solutions for dry toilets solving problems with smell, cleaning and flies can be made in collaboration between a design engineer and a biologist using biomimetic design methods. The solutions have the potential to offer significant improvements compared to conventional non-water-based sanitation.

Polycyclic Polyprenylated Acylphloroglucinol Congeners Possessing Diverse Structures from Hypericum henryi.

Polycyclic polyprenylated acylphloroglucinols (PPAPs) are a class of hybrid natural products sharing the mevalonate/methylerythritol phosphate and polyketide biosynthetic pathways and showing considerable structural and bioactive diversity. In a systematic phytochemical investigation of Hypericum henryi, 40 PPAP-type derivatives, including the new compounds hyphenrones G-Q, were obtained. These compounds represent 12 different structural types, including four unusual skeletons exemplified by 5, 8, 10, and 17. The 12 different core structures found are explicable in terms of their biosynthetic origin. The structure of a known PPAP, perforatumone, was revised to hyphenrone A (5) by NMR spectroscopic and biomimetic synthesis methods. Several compounds exhibited inhibitory activities against acetylcholinesterase and human tumor cell lines. This study deals with the structural diversity, function, and biogenesis of natural PPAPs.

Green Synthesis of Carbon- and Silver-Modified Hierarchical ZnO with Excellent Solar Light Driven Photocatalytic Performance

Superstructured ZnO has been the focus of intensive study due to its promising diverse applications. Here, we demonstrate a facile synthesis of hierarchical ZnO particles hybridized with carbon and silver via a simplified bioprocess using yeast mold broth. Better than traditional microbial and biomimetic methods, our microbe-free strategy offers superior ease-of-preparation with minimal negative environmental impact. The relevant reaction parameters including zinc precursor concentration, broth pH value, and broth content were systemically investigated to control the particle morphologies from solid microrod to mesocrystals of porous microcylinder, nanodisk, nanocone, nanoflower, and microhamburger. Silver nanoparticles were facilely deposited by photoreduction in the broth. The resultant ZnO@C–Ag composite exhibits a significant improvement in the solar light-irradiated photodegradation of methylene blue solution.

Approach to biomimetic design. Learning and application

Learning biomimetic design methods can be difficult and involve a long period of time, previous experiences have shown that the application of biomimetics in industrial design and product development projects requires an adaptation to traditional methods through a simpler model and a learning system. There are various biomimetic design processes, adaptation, integration and application corresponds to objectives of each project. A learning method for the application of biomimetics in design projects, step by step or globally, is presented. The knowledge of biological principles and translating them into engineering principles underlie each method, learning is augmented by adding methods based on creativity and functional analysis to achieve innovative products thanks to a biomimetic approach.

Evaluating toxicity of heavy fuel oil fractions using complementary modeling and biomimetic extraction methods.

The toxicity of chemically dispersed heavy fuel oil (HFO) and 3 distillate fractions to rainbow trout (Oncorhynchus mykiss) embryos was evaluated using the PETROTOX model and a biomimetic extraction technique that involved passive sampling of oil-contaminated test media with solid-phase microextraction (SPME) fibers. Test solutions for toxicity testing were generated using a combination of dispersant and high-energy mixing. The resulting water accommodated fractions (WAF) provided complex exposure regimens that included both dissolved hydrocarbons and oil droplets. The toxicity of the various fractions differed by approximately 3 orders of magnitude when expressed on the basis of WAF dilution. Using detailed compositional data, the PETROTOX model predicted the speciation of hydrocarbons between dissolved and oil droplet phases and explained observed toxicity based on computed dissolved phase toxic units (TUs). A key finding from model calculations was that dissolved hydrocarbon exposures and associated TUs were a nonlinear function of WAF dilution, because dissolved hydrocarbons were largely controlled by the dissolution of oil droplets that were transferred in WAF dilutions. Hence, oil droplets served to "buffer" dissolved concentrations in WAF dilutions at loadings greater than 1 mg/L, resulting in higher dissolved concentrations and TUs than expected based on dilution. The TUs computed at each WAF dilution explained the observed toxicity among the HFO and fractions to within a factor of 3. Dissolved material measured by SPME showed a consistent relationship with model-predicted TUs, confirming the utility of this approach for providing an integrated measure of exposure to bioavailable hydrocarbons. These 2 approaches provide complementary tools for better defining bioavailability of complex petroleum substance.

Biomimetic Creation of Surfaces on Porous Titanium for Biomedical Applications

Titanium and titanium alloys have been extensively studied for many applications in the area of bone tissue engineering. However, dense titanium is prone to lead into aseptic loosening due to their high elastic modulus compared to natural bone. One way to lower the elastic modulus is to produce a porous structure of the metallic alloy by adjusting its porosity. Another concern is the bioinertness of titanium that have no direct chemical bonding with surrounding tissue. One approach to improve the healing process is the application of a calcium phosphate coating onto the surface of biomedical devices and implants. Biomimetic creation of surface using alkali heat treatment with silica addition was employed in this study. The porosity of the samples ranges from 60% to 70%. It was demonstrated that the biomimetic methods are suitable for inducing apatite on the titanium alloys surface.

Investigations of corrosion on the surface of titanium substrate caused by combined alkaline and heat treatment

In this research, the structure changes along the depth of gradient layers of titanium substrate, after etching with NaOH and subsequent thermal treatment at various temperatures between 300 and 800°C, were investigated by XRD, FTIR and AES. Particularly, the changes of Ti substrate after etching with NaOH, subsequent ionic exchange of Na+ with Ca2+ ions and thermal treatment at 700°C were analysed. Due to this approach, it was possible to get insight into the chemical changes and changes of Ti oxidation states and consequent phase analysis, along the depth of the titanium oxide coatings.In addition, Secondary Electron Imaging (SEI) showed very interesting nanotopology of all samples. Particularly interesting topology, consisting of very thin nano-designed walls between mutually interconnected pores, was observed for the sample in which Na+ were replaced with Ca2+ ions. This structure might be suitable for deposition of hydroxyapatite by biomimetic or plasma methods and as an appropriate scaffold for cell adhesion and proliferation.

Biomimetic and bioinspired synthesis of titania and titania-based materials

Titania, one of the most important metal oxides, is extremely useful in a broad range of applications due to its unique physical/chemical properties as well as good biocompatibility. Inspired by the exquisite biomineralization process in nature, biomimetic and bioinspired methods which utilize biomolecules and their mimics as the inducers have been evolved as a novel protocol for facile, efficient synthesis of titania and titania-based materials. Compared to the most commonly employed sol–gel, hydrothermal methods, the biomimetic and bioinspired methods are often conducted under much milder conditions (aqueous solution, neutral or near neutral pH, ambient temperature and pressure). In this review, the representative advances have been highlighted for the biomimetic mineralization of titania and titania-based materials over the past decades. According to the types of inducers, the biomimetic and bioinspired synthesis of titania with noncrystalline and crystalline phase via proteins, designed peptides and their mimics have been reviewed. Moreover, the synthesis of titania-based materials through this biomimetic and bioinspired strategy coupled with self-assembly or bioadhesion has also been presented. This review may shed light on the exploration of a green, controllable platform for synthesis of diverse kinds of inorganic materials.

Transfer of Natural Micro Structures to Bionic Lightweight Design Proposals

The abstraction of complex biological lightweight structure features into a producible technical component is a fundamental step within the transfer of design principles from nature to technical lightweight solutions. A major obstacle for the transfer of natural lightweight structures to technical solutions is their peculiar geometry. Since natural lightweight structures possess irregularities and often have extremely complex forms due to elaborate growth processes, it is usually necessary to simplify their design principles. This step of simplification/abstraction has been used in different biomimetic methods, but so far, it has an arbitrary component, i.e. it crucially depends on the competence of the person who executes the abstraction. This paper describes a new method for abstraction and specialization of natural micro structures for technical lightweight components. The new method generates stable lightweight design principles by using topology optimization within a design space of preselected biological archetypes such as diatoms or radiolarian. The resulting solutions are adapted to the technical load cases and production processes, can be created in a large variety, and may be further optimized e.g. by using parametric optimization.

Benzene adsorption at the aqueous (0 1 1) α-quartz interface: is surface flexibility important?

Atomistic simulations of molecular adsorption onto inorganic substrates under aqueous conditions can be used to guide the rational design of new materials, fabricated using biomimetic methods. The success of such work depends critically on the model used. Here, we investigate the impact of using a rigid structural model of the (0 1 1) α-quartz surface, over a fully flexible model, on the calculated free energy change in the adsorption of a single molecule of benzene (a simple analogue of the amino acid phenylalanine) from liquid water. Subtle differences in the mobility of the adsorbate close to the surface result in the free energy of adsorption being overestimated by the rigid model, relative to the fully flexible case. Moreover, we find that the distribution of bound configurations of the adsorbate at their respective free energy minima is different between the two models.

Comparative study of mesenchymal stem cells osteogenic differentiation on low‐temperature biomineralized nanocrystalline carbonated hydroxyapatite and sintered hydroxyapatite

Hydroxyapatite with different characteristics in terms of morphology and chemistry were prepared via conventional sintering and low temperature biomimetic mineralization methods. The biomineralization route introduced nanocrystalline carbonate-substituted hydroxyapatite (n-CHA) with needle-like crystals ranging 20-30 nm whereas sintered HA (S-HA) comprised of polygonal grains ranging 2-5 μm. The response of fibroblastic cells was investigated using the extract of the samples whereas Wistar rat-derived mesenchymal stem cells (MSCs) were evaluated on top of each sample while maintaining in an osteogenic-free medium. The proliferation, activity, and morphology of adherent MSCs were determined at different culturing periods. The osteogenic differentiation of MSCs was also assayed by determining expression of runx2, osteonectin, osteopontin, and osteocalcin genes using real time-PCR analysis. The fibroblastic cells exhibited better proliferation rate at the presence of n-CHA compared to S-HA. Furthermore, the MSCs attached and spread well on both n-CHA and S-HA with better proliferation rate and alkaline phosphatase activity on n-CHA. Interestingly, the osteogenic differentiation of MSCs on n-CHA was confirmed by the expression of bone specific proteins whereas poor expression of these proteins was detected for the cells on S-HA. The results showed that the role of morphology, crystallinity, and chemistry of hydroxyapatite is crucial for osteogenesis differentiation of MSCs. The results predict osteoinductivity of n-CHA, because MSCs differentiation occurred at the absence of osteogenic medium. However, in vivo data are also required to support this suggestion.

Coming out of its shell: Biomimetic methods for metallic nanostructured mesoscopic model fabrication

For several decades scientists have been trying to understand the laws of biological growth and morphogenesis, with materials scientists and engineers making models of wonderful natural creations in order to reproduce their functional properties. The fact is that millions of years of evolution have created materials with characteristics that are still unattainable for artificial materials. A well-known example is the lotus leaf phenomenon, i.e. the lotus leaf self-cleaning ability, which has been well studied and widely applied in technology. A number of papers are devoted to studies of the structure of the natural shells of molluscan shellfish, which exhibit mechanical properties that are currently unfeasible for synthetic materials. Among the unsolved problems of biomimetics is that of reproducing the structure of nacre exhibiting a phenomenal external load stability. An intensive search is

Advances in using passive sampling techniques to measure bioavailability and toxicity of organic contaminants in sediment

Passive sampling techniques have been used as biomimetic extraction methods to measure the bioavailability and toxicity of organic contaminants in sediment. The advantages and disadvantages of the commonly used passive samplers including semi-permeable membrane device, polyethylene device, polyoxymethylene and solid-phase microextraction are reported. The challenges of using passive samplers in sediment risk assessment are discussed, and the possible solutions and future studies are also proposed.