Biomimetic Methods Research Articles

Bioinspired and biomimetic silk spinning

Abstract Spiders and silkworms are outstanding material and engineering masters in nature. They design and spin silk fibers with unrivaled mechanical properties by utilizing the most simple and green approach. To emulate the intelligence of spiders and silkworms in the design and production of silk fibers, a variety of artificial spinning methods have been developed in the lab. These bioinspired and biomimetic strategies significantly improved the mechanical performance of the regenerated silk fibers and provided possibility for further functionalization of the fibers. This review, therefore, provides a summary of methods to design, spin and functionalize regenerated silk fibers through bioinspired and biomimetic approaches. Here, the bioinspired and biomimetic spinning methods are introduced as four different categories, includes: (i) mimicking the natural spinning environments; (ii) mimicking the geometries of the spinning ducts; (iii) producing the silk spinning dope with nematic structures; as well as (iv) combined biomimetic spinning strategies.

Biomimetic strategies to produce catalytically reactive CuS nanodisks.

Copper sulfide materials have diverse applications from cancer therapy to environmental remediation due to their narrow bandgap and easily tuned plasmon. The synthesis of these materials often involves toxic reagents and harsh conditions where biomimetic methods may provide opportunities to produce these structures under sustainable conditions. To explore this capability, simple amino acids were exploited as biological ligands for the ambient synthesis of CuS materials. Using an aqueous-based approach, CuS nanodisks were prepared using acid-containing amino acid molecules that stabilize the materials against bulk aggregation. These structures were fully characterized by UV-vis analysis, transmission electron microscopy, dynamic light scattering, atomic force microscopy, selected area electron diffraction, and X-ray diffraction, which confirmed the formation of CuS. The materials possessed a vibrant plasmon band in the near IR region and demonstrated enhanced photocatalytic reactivity for the advanced oxidation of organic dyes in water. These results demonstrate a room temperature synthetic route to optically important materials, which could have important application in catalysis, optics, nanomedicine, etc.

State of the art and future challenges for polycyclic aromatic hydrocarbons is sediments: sources, fate, bioavailability and remediation techniques

Polycyclic aromatic hydrocarbons (PAHs) are amongst the most abundant contaminants found in the aquatic environment. Due to their toxicity and carcinogenicity, their sources, fate, behaviour, and cleanup techniques have been widely investigated in the last several decades. When entering the sediment-water system, PAH fate is determined by particular PAH and sediment physico-chemical properties. Most of the PAHs will be associated with fine-grained, organic-rich, sediment material. This makes sediment an ultimate sink for these pollutants. This association results in sediment contamination, and in this manner, sediments represent a permanent source of water pollution from which benthic organisms may accumulate toxic compounds, predominantly in lipid-rich tissues. A tendency for biomagnification can result in critical body burdens in higher trophic species. In recent years, researchers have developed numerous methods for measuring bioavailable fractions (chemical methods, non-exhaustive extraction, and biomimetic methods), as valuable tools in a risk-based approach for remediation or management of contaminated sites. Contaminated sediments pose challenging cleanup and management problems, as conventional environmental dredging techniques are invasive, expensive, and sometimes ineffective or hard to apply to large and diverse sediment sites. Recent studies have shown that a combination of strategies including in situ approaches is likely to provide the most effective long-term solution for dealing with contaminated sediments. Such in situ approaches include, but are not limited to: bioaugmentation, biostimulation, phytoremediation, electrokinetic remediation, surfactant addition and application of different sorbent amendments (carbon-rich such as activated carbon and biochar) that can reduce exposure and limit the redistribution of contaminants in the environment.

Regulation of dentin remineralization progress by non-collagenous protein analogues

The use of various biomimetic methods to achieve remineralization of demineralized dentin and the formation of an organic matrix-inorganic mineral complex with a certain mechanical strength has been a research hotspot in recent years in the field of stomatology, and it also provides a new idea for the restoration of dentin defect. Dentin biomineralization is a process that simulates the mineralization of biological tissue in nature in which the remineralization of dentin collagen is induced and regulated by organic macromolecules. This review summarizes the process of remineralization of decalcified dentin regulated by non-collagenous protein analogues in vitro.

Novel osteogenic growth peptide C-terminal pentapeptide grafted poly(d,l-lactic acid) improves the proliferation and differentiation of osteoblasts: The potential bone regenerative biomaterial

Poly(d,l-lactic acid) (PDLLA) is widely used for bone regenerative engineering, because of its proven biocompatibility and biodegradability. However, the major limitation of PDLLA is its cell recognition and low hydrophilicity. The objective of this study was to develop a novel bioactive poly(d,l-lactic acid) tethered with osteogenic growth peptide (OGP), which has been confirmed as one of the important growth factors related to bone repair/regeneration. The biomimetic material modification methods were utilized that maleic anhydride-modified poly(d,l-lactic acid) (MPLA) as raw material, the active C-terminal pentapeptide OGP(10–14) were covalently grafted onto the side chain of MPLA through amide reaction using 1‑ethyl‑3‑(3‑dimethyl aminopropyl) carbodiimide hydrochloride (EDC) and N‑hydroxysuccinimide (NHS) as the condensing agent to produce a new biopolymer (OGP(10–14)-MPLA). The OGP(10–14)-MPLA were further characterized with the Fourier transform infrared spectrometry, amino acid analyzer, elementary analysis, X-ray photoelectron spectroscopy. The results revealed that OGP(10–14) was successfully modified MPLA and its coupling efficiency was 12.40%. The data from both contact angle and water absorption showed the better hydrophilicity of OGP(10–14)-MPLA, compared with MPLA. Also, we found that OGP(10–14)-MPLA could improve the proliferation, differentiation, and mineralization of osteoblasts, indicating that the novel OGP(10–14)-MPLA has the better biocompatibility and is more osteoinductive. In conclusion, the OGP(10–14) modified MPLA have the potential for bone regenerative engineering.

Synthesis of disulfide-rich heterodimeric peptides through an auxiliary N, N-crosslink

Insulins, relaxins, and other insulin-like peptides present a longstanding synthetic challenge due to their unique cysteine-rich heterodimeric structure. While their three disulfide signature is conserved within the insulin superfamily, sequences of the constituent chains exhibit considerable diversity. As a result, methods which rely on sequence-specific strategies fail to provide universal access to these important molecules. Biomimetic methods utilizing native and chemical linkers to tether the A-chain N-terminus to the B-chain C-terminus, entail complicated installation, and require a unique proteolytic site, or a two-step chemical release. Here we present a strategy employing a linkage of the A- and B-chains N-termini offering unrestricted access to these targets. The approach utilizes a symmetrical linker which is released in a single chemical step. The simplicity, efficiency, and scope of the method are demonstrated in the synthesis of insulin, relaxin, a 4-disulfide insulin analog, two penicillamine-substituted insulins, and a prandial insulin lispro.

Solution Effects on Peptide-Mediated Reduction and Stabilization of Au Nanoparticles.

Biomimetic methods for the preparation and application of inorganic nanomaterials represent a unique avenue to sustainably generating functional materials with long-term activity. Typically, for the fabrication of these structures, the peptide is mixed with metal ions in solution prior to the addition of an exogenous reductant such as NaBH4, leading to nanoparticle nucleation and growth. In biological systems, strong reductants such as NaBH4 are not available, thus different metal ion reduction methods must be exploited. Recent work has shown that the AuBP1 peptide (WAGAKRLVLRRE), a Au binding peptide with an N-terminal tryptophan, can spontaneously reduce Au3+ without an exogenous reductant. Remarkably, this system initially demonstrated the formation of large Au aggregates that disassemble to form individual Au nanoparticles, stabilized by the peptide bound to the inorganic surface. In this contribution, we demonstrate the significant effects of aqueous solvent-processing conditions (pH, ionic strength, and ion composition) on the rate of particle evolution. Understanding how such effects alter the metal ion reduction process and subsequent nanoparticle fabrication is important in controlling the final structure/function relationship of the resultant peptide-capped materials. This work identifies conditions that may enhance nanoparticle synthesis using biomimetic approaches where the peptide has complete control over the complexation, reduction, nucleation, and growth of nanomaterials.

The mechanoresponsive self-assembly of spiropyran doped films with dual sensitivity

Spiropyran as photo- and mechano- response material has attracted great attention for wide applications. However, there are few reports on the mechanoresponsive self-assembly of spiropyran with tunable morphologies. In this work, spiropyran doped PDMS films with mechanic and photo dual response are fabricated by novel biomimetic methods. Interestingly, the morphologies of these films can be transformed from smooth surface to small hole structures due to the self-assembly of spiropyran. Only mechanical forces can induce the morphological changes of the films accordingly the conversion of ring-closed spiropyran and ring-opened merocyanine. In addition, these films exhibit good photoresponsive properties: reversible changes of UV-Vis absorption, colour and wettability.

Cellular behaviours of bone marrow-derived mesenchymal stem cells towards pristine graphene oxide nanosheets.

Graphene oxide (GO), the derivative of graphene with unique properties, has attracted much attention for applications in dental implants. The aim of this study was, by two biomimetic cell culture methods, to investigate the quantitative relationship between the concentration of pristine GO nanosheets and their cellular behaviours towards bone marrow-derived mesenchymal stem cells (BMSCs). The cells were firstly characterized according to their morphology, self-renewal capabilities and multipotency. Subsequently, adhesion density, proliferation, alkaline phosphatase activity and mineralization of BMSCs treated with various concentrations of GO were analysed. In addition, osteogenic-related proteins were measured for further verification of the GO-induced osteogenic differentiation. Pristine GO nanosheets inhibited the proliferation of BMSCs at a high concentration of 10μg/mL during the first 3days with two seeding methods and facilitated proliferation of BMSCs at a low concentration of 0.1μg/mL after 5days with a sequential-seeding method compared to a co-seeding method. Analogously, osteogenic differentiation was promoted when BMSCs were treated with 0.1μg/mL of GO. Both the proliferation and differentiation showed concentration-dependent behaviour. Interestingly, Wnt/β-catenin signalling pathway appeared to be involved in osteogenic differentiation induced by pristine GO nanosheets. Pristine GO nanosheets at a concentration of 0.1μg/mL provide benefits to promote BMSCs proliferation and osteogenesis under a sequential-seeding method, contributing to the use of GO for dental implantation.

Preparation of Hydroxyapatite/Tannic Acid Coating to Enhance the Corrosion Resistance and Cytocompatibility of AZ31 Magnesium Alloys

Hydroxyapatite/tannic acid coating (HA/TA) were prepared on AZ31 magnesium alloys (AZ31) via chemical conversion and biomimetic methods. The characterization and properties of the coating were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), corrosion testing, MC3T3-E1 cell proliferation assay, and MC3T3-E1 cell morphology observation. The results showed that tannic acid as an inducer increased the number of nucleation centers of hydroxyapatite and rendered the morphology more uniform. Compared to bare AZ31 magnesium (Mg) alloys (Ecorr = −1.462 ± 0.006 V, Icorr = (4.8978 ± 0.2455) × 10−6 A/cm2), the corrosion current density of the HA/TA-coated magnesium alloys ((5.6494 ± 0.3187) × 10−8 A/cm2) decreased two orders of magnitude, and the corrosion potential of the HA/TA-coated Mg alloys (Ecorr = −1.304 ± 0.006 V) increased by about 158 mV. This indicated that the HA/TA coating was effectively protecting the AZ31 against corrosion in simulated body fluid (SBF). Cell proliferation assays and cell morphology observations results showed that the HA/TA coating was not toxic to the MC3T3-E1 cells.

One-Pot Synthesis of Multiple Protein-Encapsulated DNA Flowers and Their Application in Intracellular Protein Delivery.

Inspired by biological systems, many biomimetic methods suggest fabrication of functional materials with unique physicochemical properties. Such methods frequently generate organic-inorganic composites that feature highly ordered hierarchical structures with intriguing properties, distinct from their individual components. A striking example is that of DNA-inorganic hybrid micro/nanostructures, fabricated by the rolling circle technique. Here, a novel concept for the encapsulation of bioactive proteins in DNA flowers (DNF) while maintaining the activity of protein payloads is reported. A wide range of proteins, including enzymes, can be simultaneously associated with the growing DNA strands and Mg2 PPi crystals during the rolling circle process, ultimately leading to the direct immobilization of proteins into DNF. The unique porous structure of this construct, along with the abundance of Mg ions and DNA molecules present, provides many interaction sites for proteins, enabling high loading efficiency and enhanced stability. Further, as a proof of concept, it is demonstrated that the DNF can deliver payloads of cytotoxic protein (i.e., RNase A) to the cells without a loss in its biological function and structural integrity, resulting in highly increased cell death compared to the free protein.

Oxidative Fragmentations and Skeletal Rearrangements of Oxindole Derivatives.

An oxidative sequence for the conversion of oxindoles to structurally distinct heterocyclic scaffolds and aniline derivatives is disclosed by the combination of a copper-catalyzed C-H peroxidation and subsequent base-mediated fragmentation reaction. In contrast to classic enzymatic (i.e., kynurenine pathway) and biomimetic methods (i.e., Witkop-Winterfeldt oxidation) for oxidative indole cleavage, this protocol allows for the incorporation of external nucleophiles. The new transformation displays broad functional group tolerance and is applicable to tryptophan derivatives, opening potential new avenues for postsynthetic modification of polypeptides, bioconjugation, and unnatural amino acid synthesis.

An FEA Study on Impact Resistance of Bio-Inspired CAD Models

The purpose of this paper is to explore the use of biomimetic methods in the design of armour systems. It focusses on biological structures found in nature that feature both rigid and flexible armours, analysing their structures and determining which are the most widely successful. A study was conducted on three bio-inspired structures built in Creo Parametric and tested using Finite Element Analysis (FEA) software to determine which structure had the best impact resistance. The study was conducted based on parameters from a study conducted on impact testing biological materials (Lee et al., 2011). The aim of the study was to discover if a bio-inspired model built using ABS (Acrylonitrile Butadiene Styrene) and silicone, based on the structure of an osteoderm would perform well under impact.

Hidroxyapatite Coating on CoCrMo Alloy Titanium Nitride Coated Using Biomimetic Method

Bone implants is a way to cure broken bones which is being developed. The implants can be made of metals, ceramics and polymers. Metallic materials commonly used are titanium (Ti), stainless steel, and metal alloys. This study used Co-based alloys, i.e. CoCrMo coated with titanium nitride (TiN) which was then coated on hidroxyapatite (HAp). The HAp coating on the surface of CoCrMo alloy was done by biomimetic methods, first by soaking the metal alloys in simulated body fluid (SBF) solution for 18, 24, and 36 hours. The immersion in the SBF solution produced white coat on the surface of the metal alloy. The layers formed were analyzed by scanning electron microscope (SEM) and characterized by x-ray diffractometer (XRD). Based on the SEM results of 36 hours treatment, the morphology of apatite crystal formed fine grains. According to XRD result, there were HAp peaks at angles 2θ 31.86, 32.25, dan 39.48. However, there were also CaCO3 peaks at angles 2θ 29.46, 36.04, and 46.79. It indicated the pure HAp is not yet formed.

Observation of impact energy absorption performance on idealised trabecular forms in laser sintered nylon

Purpose This paper aims to investigate whether the trabecular architecture found in natural bone can be effectively replicated through the selective laser sintering process of Nylon P2200. Design/methodology/approach Trabecular bone was idealised into a scaled up hexagonal cell proven to replicate the natural structure. The structure was modelled in Solidworks 2013 to form a network of interlinking cells. The specific property analysed was the structure toughness through the measurement of the energy absorbed before sample fracture. Findings It was found that the impact absorption can be increased with the integration of a greater number of trabecular cells producing a finer resolution and not necessarily by increasing the trabecular size. The information gained from this research may be useful in the design of impact and shock absorbing components, with an emphasis on efficient use of material mass. Research limitations/implications Designers and engineers may find biomimetic methods of absorbing shock and impact an efficient alternative consideration in design applications. Practical implications The trabecular architecture should be designed so as to be weaker than the bounding surfaces, ensuring that the individual trabecular experience failure first, maximising their energy absorbing capability through increasing the period of deceleration. The simplest way of doing this is to ensure the rod thickness is less than the bounding material thickness. Originality/value This work documents original testing of both the RP material and consolidated design of samples of idealised bone structures. It builds on previous work in the area and through the results of empirical testing, derives recommendations for further considerations in this area of design and manufacture of biomimetic structures.

Aqueous Based Semiconductor Nanocrystals

This review summarizes traditional and recent nonconventional, bioinspired, methods for the aqueous synthesis of colloidal semiconductor quantum dots (QDs). The basic chemistry concepts are critically emphasized at the very beginning as these are strongly correlated with the selection of ligands and the optimal formation of aqueous QDs and their more sophisticated structures. The synergies of biomimetic and biosynthetic methods that can combine biospecific reactivity with the robust and strong optical responses of QDs have also resulted in new approaches to the synthesis of the nanoparticles themselves. A related new avenue is the recent extension of QD synthesis to form nanoparticles endowed with chiral optical properties. The optical characteristics of QD materials and their advanced forms such as core/shell heterostructures, alloys, and doped QDs are discussed: from the design considerations of optical band gap tuning, the control and reduction of the impact of surface traps, the consideration of charge carrier processes that affect emission and energy and charge transfer, to the impact and influence of lattice strain. We also describe the considerable progress in some selected QD applications such as in bioimaging and theranostics. The review concludes with future strategies and identification of key challenges that still need to be resolved in reaching very attractive, scalable, yet versatile aqueous syntheses that may widen the scope of commercial applications for semiconductor nanocrystals.

Experimental and Finite Element Investigations of Damage Resistance in Biomimetic Composite Sandwich T-Joints.

Composite sandwich structural joints, such as T-joints, are used in many different composite applications to transfers the load orthogonally between two sandwich elements. However, these joints connecting the sections can represent the weakest link in sandwich composite structures due to the lack of reinforcement in the out-of-plane direction. Therefore, this paper presents a new methodology for the design and analysis of composite sandwich T-joints using new biomimetic fabrication methods. The fabricated idea comes from biological fixed joints as an evolutionary alteration processes of trunk-branches of trees. It offers unique attributes to optimize the continuous fiber paths for minimum stress concentrations and multi-sandwich layers to increase the bending stiffness and strength. The focus is on how the biomimetic technique can improve sandwich T-joint structures by increasing their strength and load carrying capability without adding a significant weight penalty. The major attention is to investigate the comprehensive failure modes in the joint numerically and verified by experiments. Investigations were conducted on three different designs of biomimetic composite sandwich T-joints under tension and bending loads. The results show significant improvements to the ultimate load up to 68% in the case of bending load and 40% in the case of pull-off load in the biomimetic sandwich T-joints compared to the reference conventional T-joint design. The final failure was significantly deferred in both load status. The FE models provided important insights into the core failure and delamination of multi-interface biomimetic T-joints.

In silico and in vitro Studies on Begomovirus Induced Andrographolide Biosynthesis Pathway in Andrographis Paniculata for Combating Inflammation and Cancer.

Andrographolide and neoandrographolide are major bioactive molecules of Andrographis paniculata, a well-known medicinal plant. These molecules exhibited varying degrees of anti-inflammatory and anticancer activities in-vitro and in-vivo. Role of begomovirus protein C2/TrAP in biosynthesis of andrographolide was identified through molecular modeling, docking and predicted results were substantiated by in vitro studies. Homology molecular modeling and molecular docking were performed to study the binding conformations and different bonding behaviors, in order to reveal the possible mechanism of action behind higher accumulation of andrographolide. It was concluded that C2/TrAP inhibit the activation of SNF1-Related Protein Kinase-1 (SnRK1) in terpenoid pathway and removes the negative regulation of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) by SnRK1, leading to higher accumulation of andrographolide and neoandrographolide in begomovirus infected plants. The binding site residues of SnRK1 docked with C2/TrAP were found to be associated with ATP binding site, substrate binding site and activation loop. Predicted results were also validated by HPTLC. This study provides important insights into understanding the role of viral protein in altering the regulation of biosynthesis of andrographolide and could be used in future research to develop biomimetic methods for increasing the production of such phytometabolites having anti-cancerous and anti-inflammatory properties.

N-Alkylation by Hydrogen Autotransfer Reactions [corrected

Owing to the importance of amine/amide derivatives in all fields of chemistry, and also the green and environmentally benign features of using alcohols as alkylating reagents, the relatively high atom economic dehydrative N-alkylation reactions of amines/amides with alcohols through hydrogen autotransfer processes have received much attention and have developed rapidly in recent decades. Various efficient homogeneous and heterogeneous transition metal catalysts, nano materials, electrochemical methods, biomimetic methods, asymmetric N-alkylation reactions, aerobic oxidative methods, and even certain transition metal-free, catalyst-free, or autocatalyzed methods, have also been developed in recent years. With a brief introduction to the background and developments in this area of research, this chapter focuses mainly on recent progress and technical and conceptual advances contributing to the development of this research in the last decade. In addition to mainstream research on homogeneous and heterogeneous transition metal-catalyzed reactions, possible mechanistic routes for hydrogen transfer and alcohol activation, which are key processes in N-alkylation reactions but seldom discussed in the past, the recent reports on computational mechanistic studies of the N-alkylation reactions, and the newly emerged N-alkylation methods based on novel alcohol activation protocols such as air-promoted reactions and transition metal-free methods, are also reviewed in this chapter. Problems and bottlenecks that remained to be solved in the field, and promising new research that deserves greater future attention and effort, are also reviewed and discussed.

Unusual adamantane type polyprenylated acylphloroglucinols with an oxirane unit and their structural transformation from Hypericum hookerianum

Hookeriones A–D (1–4), adamantane type polycyclic polyprenylated acylphloroglucinols (PPAPs), and hookeriones E–H (5–8), 1,9-seco-adamantane type PPAPs, were isolated from Hypericum hookerianum, along with six known analogues. The structures of 1–8, sharing a common 28,29-epoxide moiety, were determined on the basis of comprehensive NMR and MS spectroscopic data. The biomimetic synthesis of 5–7 from the biogenetically precursors 1–3 was performed, respectively. Absolute configurations of these new PPAPs were further defined by electronic circular dichroism (ECD) and biomimetic synthesis methods.