Introduction: The LL-37 peptide, the only cathelicidin secreted in human organisms, can resist numerous pathogens as a part of an immune system. The efficiency of LL-37 antimicrobial action is dependent on the bacterial membrane composition, the percentage of phospholipid classes, their mutual proportions, and the types of fatty acid chains. The presence of choline in the growth environment for bacteria alternates the composition and physicochemical properties of their membranes, which then affects the LL-37 activity. In this study, the influence of the antimicrobial LL-37 peptide on the phospholipid monolayers at the liquid—air interface mimicking the membranes of Legionella gormanii bacteria was analyzed.

Methods: The Langmuir monolayer technique was used to prepare model membranes composed of individual classes of phospholipids (phosphatidylcholine (PC), phosphatidylethanolamine (PE), cardiolipin (CL), phosphatidylglycerol (PG), and their mixtures isolated) from L. gormanii bacteria supplemented or not with exogenous choline. In order to determine the peptide’s mechanism of action, penetration tests were carried out for the phospholipid monolayers compressed to a surface pressure of 30 mN/m, and the peptide was then dispensed to the subphase. The changes in mean molecular area were observed over time.

Results: The results show the diversified effect of LL-37 on the phospholipid monolayers depending on the bacteria growth conditions. The choline presence in the medium affects the molecular profile of phospholipids in the bacterial membranes, determining the greater activity of the peptide. Our findings demonstrate that notable peptide insertion and disruption of the lateral packing and ordering can cause membrane destabilization.

Conclusions: Changes in membrane structure due to its interactions with LL-37 demonstrate a feasible mechanism of peptide action at a molecular level. Its determination is crucial for the design and development of antimicrobial peptides as an alternative to conventional antibiotics.

Polymers with photoluminescent centers in their structure are of great interest in the field of bioimaging and could be artificial analogs to green fluorescent protein (GFP) from jellyfish [1]. Along with intrinsic photoluminescence, jellyfish also demonstrate self-healing of their organs, which allow the creatures to survive in aquatic environments [2]. Polymer metal complexes (PMCs) of europium(III) and terbium(III) could be artificial analogs to GFP due to their excellent luminescent properties (Tb³⁺ and Eu³⁺) and to the bioinertness of PDMS.

Europium(III) and terbium(III)-containing 2,2'-bipyridine-6,6'-dicarboxamide-co-polydimethylsiloxanes (Eu-Bipy-PDMS and Tb-Bipy-PDMS) [3] and their low-molecular complexes [Tb(BDCA)₂(H₂O)]Cl₃ and [Eu(BDCA)₂(H₂O)]Cl₃ [4] were synthetized by polycondensation and complexation reactions. The structure of the obtained complexes was confirmed by NMR, IR spectroscopy, and XRD analysis. A tensile property study was carried out on a Shimadzu EZ-L-5kN testing machine (RT, constant stretching rate of 10 mm∙min^–1, sample shape ISO 37 type 3). Photoluminescence spectra and quantum yields (QYs) were studied using a HORIBA Fluorolog-3 spectrofluorometer with an integrating sphere (101 mm in diameter) at RT.

Eu-Bipy-PDMS and Tb-Bipy-PDMS show QYs of 10.5% and 18.5%. The PMCs' structure enables the formation of coordinatively saturated complexes of lanthanide ions and provides good tensile properties to Eu-Bipy-PDMS (1.55 MPa, 185%) and Tb-Bipy-PDMS (1.48 MPa, 190%). The self-healing efficiency of PMCs exceed 90%. [Tb(BDCA)₂(H₂O)]Cl₃ and [Eu(BDCA)₂(H₂O)]Cl₃ show high QYs of 36.5% and 12.6%, respectively, and can retain them after encapsulation in a semitransparent biocompatible polyethyleneglycol matrix (11.2% and 25.3%, respectively) .

Both obtained self-healing luminescent lanthanide-containing PMCs and their low-molecular analogs could be used in bioimaging and theranostics [5].

Financial support for this study was provided by St. Petersburg State University (project 94124215).

1. Zhang, Y. et.al. // J. Mater. Chem. B 2013, 1, 132–148.
2. Liu, Y. et.al. // Nat Commun 2022, 13, 1338.
3. Miroshnichenko, A.S. et.al. // ACS Appl. Polym. Mater. 2022, 4, 2683–2690.
4. Miroshnichenko, A.S. et.al. // Polymers 2022, 14, 5540.
5. Ranjan, S. et.al. // Nanomedicine 2015, 10, 1477–1491.

In complex and dynamic environments, traditional pursuit–evasion studies may face challenges in offering effective solutions. This paper aims to provide a novel approach that approximates a general pursuit–evasion game from a neurodynamics perspective instead of formulating the problem as a traditional differential game. In this paper, the neurodynamics-based approach aims to overcome the limitations of the traditional approach and improve the performance of the evaders in dynamic and uncertain environments. A bio-inspired neural network is proposed that approximates a general pursuit–evasion game from a neurodynamic perspective. The bio-inspired neural network is topologically organized to represent the environment with only local connections, and the dynamics of neural activity are characterized by a neurodynamic model. The pursuer has global effects on the whole neural network, while the obstacles only have local effects to guarantee the robot avoids collisions. The real-time collision-free evasion trajectories are generated through dynamic neural activities. Simulation results indicate that the proposed approach is able to guide evader robots to evade the pursuer in complex environments with static, moving, and sudden-change obstacles. In addition, the comparison studies illustrate that the proposed approach is effective and efficient in complex and dynamic environments. This paper brings new insights into the application of the bio-inspired neural network in the field of robotics and also presents many potential practical application scenarios.

The regulation of body temperature and the mastery of thermal radiation control stand as fundamental survival mechanisms for diverse animal species. Evolution over millions of years has fine-tuned natural systems, particularly in cold-blooded organisms like insects, as well as those facing extreme temperature conditions, such as polar bears, Arctic foxes, and dromedaries. These creatures have developed unique integumentary features to optimize thermal radiation absorption and regulation [1].

This conference contribution delves into selected natural case studies, focusing on the intricate designs found in butterfly wings and animal furs. These natural structures, honed by evolution, serve as a wellspring of inspiration for developing innovative materials with enhanced energy efficiency for infrared absorption and thermal insulation. By examining the biological adaptations that enable these organisms to excel in thermal regulation, we can draw insights to inform the design, development, and fabrication of materials that mimic these features [2].

Through the exploration of bioinspired applications, this presentation will underscore the potential for translating biological principles into practical solutions. By bridging the realms of biology and materials science, attendees will gain a deeper understanding of how nature's innovations can guide the creation of advanced structures capable of efficient thermal management. This interdisciplinary approach holds promise for applications in diverse fields contributing to the development of sustainable and energy-efficient solutions.

[1] K. Delmote, O. Deparis, S. R. Mouchet, to be submitted.

[2] S. R. Mouchet, O. Deparis, Natural Photonics and Bioinspiration, Artech House, Boston & London, 2021.

1. Introduction

Recent advancements in tissue engineering highlight the potential for 3D scaffold functionalization using biomolecules to induce specific actions within the material's microenvironment. Vitamin D3, a key biomolecule for bone tissue regeneration, plays a crucial role in modulating calcium and phosphorus absorption, supporting the functions of osteoblasts and osteoclasts. Insufficient levels of vitamin D3 can lead to the development of thin and brittle bones, while its anti-inflammatory properties and immune system modulation further emphasize its significance.

This study aimed to obtain 3D scaffolds functionalized with vitamin D3 based on sol-gel Cerium (Ce) doped mesoporous bioactive glasses (MBGs) and Spongia agaricina (SA), a natural marine sponge.

The research assessed the functionalized scaffold capabilities for in vitro osteogenic differentiation of dental pulp stem cells and their genotoxicity towards osteoblast cells.

1. Methods

The template replica technique was used for 3D scaffold preparation based on Ce-doped MBGs in the 70SiO₂-(26-y) CaO-4P₂O₅-yCeO₂ system (y denotes 0, 1, and 3 moles) and SA as a sacrificial template. The green scaffolds were thermally treated in two stages up to the final temperature of 1200 °C.

The obtained scaffolds were analyzed by Scanning electronic microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and microcomputed tomography (micro-CT). The effect of vitamin D3 functionalization on biological properties was also investigated by in vitro assays.

1. Results

Analysis using Micro-CT unveiled that all scaffolds displayed an interconnected porous structure, with pore diameters predominantly falling within the range of 143.5 to 213.5 μm, which can promote effective bone ingrowth. Vitamin D3 functionalization of the scaffolds promoted bioactivity and osteogenic differentiation of dental pulp stem cells, leading to increased secretion of calcium and osteocalcin.

1. Conclusions

The results showed that functionalized 3D scaffolds are safe, do not damage the DNA cells, and promote in vitro osteoinduction.

Introduction

Skin tissue engineering is a novel approach used to treat skin damage that has gained popularity in recent times. Hydrogel scaffolds are commonly used to promote wound healing. Studies have shown that chitosan, alginate, and ascorbic acid are highly effective in this regard [1, 2, 3, 4]. Ascorbic acid, used as a biological agent, plays a significant role in wound healing by increasing repair intermediaries and decreasing inflammation at the wound site [5]. Applying hypoxia has been shown to enhance the therapeutic performance of mesenchymal stem cells [6]. Moreover, hypoxia-inducible factor-1 (HIF-1) plays a crucial role in wound healing and remodeling [7]. The aim of our study is to investigate the role of biological agents and MSCs loaded onto biomimetic constructs based on chitosan—alginate hydrogel and determine their performance under hypoxic conditions.

Methods:

Biomimetic constructs based on chitosan—alginate hydrogel were mixed with ascorbic acid and cross-linked with CaCl2.The scaffold's physicochemical properties, including swelling and biodegradation rates, wettability, and FTIR analysis, were assessed. Further analysis was conducted using MTT, DAPI, and H&E staining. The study investigated the expression of key genes (HIF-1α, VEGF-A, and TGF-β1) involved in the healing of skin wounds under hypoxic and normoxic conditions using real-time PCR.

Results and conclusions

The study revealed that the biomimetic construct based on chitosan—alginate hydrogel was highly porous, biodegradable, and had a high swelling capacity. The hydrogel was not only hydrophilic but also compatible with blood. The hydrogel provided a suitable substrate for cell growth and proliferation, as indicated by MTT, DAPI, and H&E staining tests. Under hypoxic conditions, MSCs showed increased expression levels of VEGF and TGF-β1 genes according to RT-PCR analysis. Based on the results, a biomimetic construct made of chitosan—alginate hydrogel seeded with hypoxic MSCs could be a promising approach to improving wound healing.

Airfoils are widely used in fluid machinery, and airfoil stall is an important reason for equipment safety hazards. Biomimetic leading-edge protuberances are considered a potential means of stall control. In this study, the Transition SST turbulence model was employed to carry out a numerical simulation on the NACA 634-021 airfoil. The airfoil consists of a leading edge with 30 protuberances, forming an unusually wide wing. This configuration has never been previously investigated and is novel to this research. The results showed that the bio-inspired airfoil reduced the maximum lift coefficient by 14.2% and advanced the stall angle by 8°. The biomimetic airfoil exhibited excellent performance after stall. The maximum lift coefficient increased by 25.1% and the lift-to-drag ratio increased by 21.8%. At high angles of attack, due to the influence of the protuberance peak attachment flow, the suction surface flow field formed an alternating distribution of expansion and contraction. This validated the correctness of the conclusion that the suction surface flow field of the biomimetic airfoil exhibits periodic distribution at low angles of attack and non-periodic distribution at high angles of attack. Biomimetic airfoils have advantages in working with large changes in the angle of attack. This provides a theoretical basis for the application of biomimetic protuberances in vertical axis wind turbines and fixed-wing drones.

Tree root systems are multifunctional plant elements that could serve as biomimetic role models for anchoring and supply systems in engineering. A previous study has established an analogy framework for the design of building foundations and coastal resilience. Due to their underground existence, research on root morphology is largely based on time-consuming and tedious manual or semi-automated processes.

In a reverse biomimetic approach, the methods of photogrammetry and parametric design were applied to the morphological analysis of coarse tree root systems, and gradually refined to produce 3D models to reliably extract design principles. Ten different root specimens across four different tree species were imaged in the field and reconstructed virtually through photogrammetry. A parametric algorithm then analyzed the generated 3D models and extracted their skeleton to access the system's topology and morphological traits (such as volume, surface area, radius, curvature, and branching angles).

Topological information together with traits provide information about biological diversity across species and allow for the identification of key strategies for root performance in specific environments. Based on the abstracted design principles, functional transfer to the conceptual design of novel bio-inspired infrastructure is carried out.

For the applicability of basic root design principles, such as the number of branches and branching angle, to the function of anchoring, a pull-out study in a granular medium was carried out. Further conceptual proposals for the design of geotechnical infrastructure based on the biological traits are currently under development. Such exploratory studies serve to develop the potential and applicability of root-inspired infrastructure.

Fish scale-inspired armor exhibits numerous advantages over conventional armor plates. This study includes hybrid scale-tissue design with scales inclined at a certain angle. The fish scale-inspired design had a curved radius of 200 mm, a length of 19 mm, a width of 12 mm and an inclination of 10°. The total size of the specimen measured 80 mm × 80 mm × 10 mm. The acrylonitrile butadiene styrene (ABS) material represented the hard scales, while thermoplastic polyurethane (TPU) mimicked the soft tissue. Low-velocity impact scenarios were investigated using the commercially available software LS-Dyna. Scales/ABS were modeled using a plastic kinematic (MAT03) material model, while the tissue/TPU were modeled using a plasticity polymer (MAT89). The effects of indenter shape (hemispherical, conical, and flat head) were studied at an impact energy and velocity of 100 J and 6 m/s. During the impact process, all impactors fully perforated the sample. The performance of the specimen was evaluated based on the specific energy absorption and damage area. The pecific energy absorbed by the conical indenter was the largest, followed by the hemispherical indenter. The bio-inspired specimens resisted the flat indenter early on, while elastic resistance on other indenters gradually increased in the elastic region. The peak forces absorbed by the hemispherical, conical and flat head indenters were 6.1 kN, 5.4 kN and 3.7 kN, respectively. The primary failure modes were shear failure and the tensile breaking of the scales. The present study highlighted the effect of indenter shape on the impact behavior of fish-scale inspired design.

Wind turbines and other fluid machinery can experience stalls during operation, leading to highly transient and heavy load fluctuations that jeopardize the structural integrity of the turbines and result in fatigue failure, significantly reducing performance. Inspired by the protuberance on the leading edge of a humpback whale's pectoral fin, eight different configurations of protuberances were added to the leading edge of a NACA 0021 airfoil segment with a span of 0.24m as a passive control method to investigate their inhibitory effect on flow separation. The protuberance structures altered the pressure distribution on the airfoil's leading edge, particularly reducing the pressure at the trough after stall, allowing the fluid to reattach to the airfoil surface and delaying the onset of dynamic stall. The most significant improvement in alleviating airfoil stall was observed with the protuberance structure composed of a quarter-circle with a radius of 0.02m and a quarter-circle with a radius of 0.01m. At an angle of attack of 22° after the original airfoil stall, the lift coefficient increased by 6.7.7%. At the initial angle of attack of 4°, the lift coefficient increased by 60.4%, and then maintained a stable linear growth at various angles, with no stall occurring at the 24° angle of attack. This study provides inspiration for the design of bionic airfoil protuberance on structures and has guiding value for practical applications.