Structures For Biomedical Applications Research Articles

Synthesis and Antibiotic Activity of Chitosan-Based Comb-like Co-Polypeptides

Infections caused by multidrug-resistant Gram-negative bacteria have been named one of the most urgent global health threats due to antimicrobial resistance. Considerable efforts have been made to develop new antibiotic drugs and investigate the mechanism of resistance. Recently, Anti-Microbial Peptides (AMPs) have served as a paradigm in the design of novel drugs that are active against multidrug-resistant organisms. AMPs are rapid-acting, potent, possess an unusually broad spectrum of activity, and have shown efficacy as topical agents. Unlike traditional therapeutics that interfere with essential bacterial enzymes, AMPs interact with microbial membranes through electrostatic interactions and physically damage cell integrity. However, naturally occurring AMPs have limited selectivity and modest efficacy. Therefore, recent efforts have focused on the development of synthetic AMP analogs with optimal pharmacodynamics and an ideal selectivity profile. Hence, this work explores the development of novel antimicrobial agents which mimic the structure of graft copolymers and mirror the mode of action of AMPs. A family of polymers comprised of chitosan backbone and AMP side chains were synthesized via the ring-opening polymerization of the N-carboxyanhydride of l-lysine and l-leucine. The polymerization was initiated from the functional groups of chitosan. The derivatives with random- and block-copolymer side chains were explored as drug targets. These graft copolymer systems exhibited activity against clinically significant pathogens and disrupted biofilm formation. Our studies highlight the potential of chitosan-graft-polypeptide structures in biomedical applications.

Long-Time Behavior of Surface Properties of Microstructures Fabricated by Multiphoton Lithography.

The multiphoton lithography (MPL) technique represents the future of 3D microprinting, enabling the production of complex microscale objects with high precision. Although the MPL fabrication parameters are widely evaluated and discussed, not much attention has been given to the microscopic properties of 3D objects with respect to their surface properties and time-dependent stability. These properties are of crucial importance when it comes to the safe and durable use of these structures in biomedical applications. In this work, we investigate the surface properties of the MPL-produced SZ2080 polymeric microstructures with regard to the physical aging processes during the post-production stage. The influence of aging on the polymeric microstructures was investigated by means of Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). As a result, a time-dependent change in Young’s Modulus, plastic deformation, and adhesion and their correlation to the development in chemical composition of the surface of MPL-microstructures are evaluated. The results presented here are valuable for the application of MPL-fabricated 3D objects in general, but especially in medical technology as they give detailed information of the physical and chemical time-dependent dynamic behavior of MPL-printed surfaces and thus their suitability and performance in biological systems.

3D printing biomimetic materials and structures for biomedical applications

3D printing biomimetic materials and structures for biomedical applications

Biomimetic micro/nano structures for biomedical applications

• Biomimetic micro/nano structures for biomedical applications are overviewed. • Fundamental and guiding principles for of micro/nano structures are summarized. • The wide application of micro/nano structures in vitiro and in vivo are discussed. • Perspectives towards biomimetic micro/nano structures are outlooked. Cell behaviors are influenced by the surrounding dynamic microenvironment where the extracellular matrix (ECM) composed of different micro/nano-structures plays a key role. Many micro/nano-structures have been developed to mimic the structure of ECM, but these structures are almost static, and fail to emulate the dynamicity and function of the ECM in vivo . Notably, certain micro/nano-structures based on shape-memory polymers (SMPs), including patterns, fibers, porous scaffolds and microspheres, have attracted increasing attention due to the unique spatiotemporal variations. The dynamical shifting of these biomimetic micro/nano-structures arising from the shape-memory effect endows the materials with unique functions, e.g. , regulating cell behaviors and prompting tissue growth. Therefore, the dynamically tunable biomimetic micro/nano-structures based on SMPs can be an ideal platform to mimic dynamic changes in the ECM structure both in vitro and in vivo . This review summarizes the latest advances in the development of the methodologies for fabricating various SMP biomimetic micro/nano structures, spatiotemporal control of cell behaviors, and broad applications in biomedical engineering. Several crucial points for future research are presented.

4D printed shape memory polymers and their structures for biomedical applications

Shape memory polymers are smart materials that produce shape changes under external stimulus conditions. Four-dimensional (4D) printing is a comprehensive technology originate from deformable materials and three-dimensional (3D) printing technology. At present, 4D printed shape memory polymers and shape-changing structures have been applied in various fields, especially in the field of biomedical science. 4D printing technology has made a breakthrough of personalized customization in the traditional medical field, providing a new direction for the further development of the biomedical field. In this review, the recent research and development of shape memory polymer, 3D printing technology, 4D printed shape memory polymers and shape-changing structures in biomedical area are present. The examples and applications of 4D printed shape memory polymers and their structures in the area of biomedical are also introduced. Based on 4D printing, stimulated by different conditions, 3D printed objects can be fabricated into various biomedical applications such as cell scaffolds, vascular stents, bone scaffolds, tracheal stents and cardiac stents by different 3D printing techniques. Finally, the application prospects, existing technical restriction and future development directions of 4D printed shape memory polymers and their structures in the biomedical field are summarized.

In silico design of self-assembly nanostructured polymer systems by multiscale molecular modeling

The fast development of digitalization and computational science is opening new possibilities for a rapid design of new materials. Computational tools coupled with focused experiments can be successfully used for the design of new nanostructured materials in different sectors, particularly in the area of biomedical applications. This paper starts with a general introduction on the future of computational tools for the design of new materials and introduces the paradigm of multiscale molecular modeling. It then continues with the description of the multiscale (i.e., atomistic, mesoscale and finite element calculations) computational recipe for the prediction of novel materials and structures for biomedical applications. Finally, the comparison of in silico and experimental results on selected systems of interest in the area of life sciences is reported and discussed. The quality of the agreement obtained between virtual and real data for such complex systems indeed confirms the validity of computational tools for the design of nanostructured polymer systems for biomedical applications.

Covalent grafting of graphene oxide on functionalized macroporous silicon

Abstract Graphene oxide (GO) is a single-atom-thick and two-dimensional carbon material that has attracted great attention because of its remarkable electronic, mechanical, chemical and thermal properties. GO could be an ideal substrate for the development of label-free optical biosensors, however, its weak photoluminescence (PL) strongly limits the use for this purpose. In this study, we developed a covalent chemical strategy in order to obtain a hybrid GO-macroporous silicon (PSi) structure for biomedical applications. The realized structure was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM)water contact angle (WCA) measurements, Fourier transform infrared spectroscopy (FTIR) and label- free optical methods based on spectroscopic reflectometry and PL analysis. Investigations showed that the hybrid structure is suitable as a transducer material for biosensing applications due to its peculiar optical properties resulting from the combination of GO and PSi.

Novel 3D electrospun polyamide scaffolds prepared by 3D printed collectors and their interaction with chondrocytes

ABSTRACTElectrospinning is significantly one of the simple and versatile methods for producing micro- and nanofibrous scaffolds. Its assembly can be modified in different ways to combine material properties with different morphological structures for biomedical applications. In this process, collector design plays an important role to determine the nanofiber orientation in electrospun nanoweb. In this work, 3D patterned scaffolds were produced by electrospinning of polyamide-66 solution on different 3D collectors that have been obtained. The aim of this work is to investigate the attachment of the chondrocyte cells on the prepared electrospun scaffolds that have different types of nanofiber orientations that could be used in tissue engineering applications.

Mechanochemically synthesized Ag-based nanohybrids with unprecedented low toxicity in biomedical applications

A simple and innovative mechanochemical approach was employed to synthesize Ag-polysaccharide nanohybrid materials that were proved to exhibit remarkable surface properties and structures for biomedical applications. The synthesized Ag nanomaterials possessed an unprecedented low cytotoxicity against human cell lines A549 and SH-SY5Y as compared to similarly reported Ag nanomaterials due to the stability and low release of Ag+ and high biocompatibility of the nanohybrids.

Cross-Point Resistive Switching Memory and Urea Sensing by Using Annealed GdOx Film in IrOx/GdOx/W Structure for Biomedical Applications

Resistive switching characteristics and urea sensing have been investigated by using annealed GdOx film in IrOx/GdOx/W cross-point memory for the first time. The annealed GdOx film shows larger polycrystalline grains as compared to as-deposited films, which is observed by high-resolution transmission electron microscope (HRTEM) and X-ray diffraction patterns (XRD). Surface roughness of the GdOx films on W nano-dome is observed by atomic force microscope (AFM). The annealed IrOx/GdOx/W cross-point memory shows resistance ratio of 1000× times higher, multi-level operation with varying current compliance (CC) from 10–300 μA, good non-linearity factor of 8.3, good dc switching cycles of > 1000 at CC of 10 μA, long read endurance of >109 cycles with pulse width of 1 μs at higher read voltage of −0.5 V, and high speed operation of 100 ns. Repeatable resistive switching characteristics at low CC of 10 μA and mechanism are due to the electric field enhancement on the W nano-dome simulated by MATLAB, which controls the O2− ions migration through polycrystalline GdOx grain boundary as well as Schottky barrier height modulation (0.59 vs. 0.39 eV). In addition, the annealed GdOx membrane in electrolyte-insulator-semiconductor (EIS) structure shows higher pH sensitivity than the as-deposited film (53.2 vs. 45.1 mV/pH) and lower drift (1.8 vs. 2.6 mV/hr) as well as lower detection of pH change (0.034). Detection of pH and urea sensing from 6 to 24 mg/dl have been measured by using cross-point memory, and the sensing mechanism is also discussed, which will be very useful for real healthcare unit in near future.

Viruses, Artificial Viruses and Virus-Based Structures for Biomedical Applications.

Nanobiomaterials such as virus particles and artificial virus particles offer tremendous opportunities to develop new biomedical applications such as drug- or gene-delivery, imaging and sensing but also improve understanding of biological mechanisms. Recent advances within the field of virus-based systems give insights in how to mimic viral structures and virus assembly processes as well as understanding biodistribution, cell/tissue targeting, controlled and triggered disassembly or release and circulation times. All these factors are of high importance for virus-based functional systems. This review illustrates advances in mimicking and enhancing or controlling these aspects to a high degree toward delivery and imaging applications.

Nanofabrication of Polymer Biosensor Structures for Biomedical Applications

This paper presents the nanofabrication of polymer biosensor structures for biomedical applications. The polymer biosensor structures were achieved using hot embossing technology. The pressure effects on the replication of patterns during the hot embossing of the polymer biosensor structures were investigated. The fabricated polymer biosensor structures with pillar arrays were applied to immunoassay biochips. The pillar shapes of the polymer biosensor structures provided large surface areas and improved the antibody-antigen interaction of the immunoassay biochips.

Bioinspired Porous ZnO Nanomaterials from Fungal Polysaccharides: Advanced Materials with Unprecedented Low Toxicityin Vitrofor Human Cells

Mechanochemically synthesized ZnO–polysaccharide nanohybrids prepared from fungal polysaccharides were proved to exhibit remarkable surface properties and structures for biomedical applications. The synthesized ZnO nanomaterials possessed an unprecedented low cytotoxicity against human cell lines A549 and SH-SY5Y (EC50: 50–100 μg mL–1) as compared to commercial ZnO nanomaterials due to the stability and low release of Zn2+ and reduced interaction nanoparticle/cells due to the high biocompatibility of the nanohybrids.

Fabricating millimeter-scale polymeric structures for biomedical applications via a combination of UV-activated materials and daily-use tools

Three-dimensional millimeter-scale polymeric structures can be fabricated by using UV-activated materials and daily-use tools for making PDMS-basedin vitrodiagnostic devices.

Tailored topography control of biopolymer surfaces by ultrafast lasers for cell–substrate studies

Nowadays, the culture surfaces used for in vitro testing must be capable of possessing an improved interface for cell interactions and adhesion. For this reason, the materials used need to have an appropriate chemistry and architecture of its surface, resembling to the extracellular matrix. Within this context, in this work we combined the advantages of natural biopolymer characteristics (chitosan) with the flexibility in surface texturing by ultrafast laser for creating functional microstructured surfaces for cell–substrate in vitro studies. A Ti:Sapphire femtosecond laser irradiation (λ=775nm and 387nm) was used for tailoring surface morphological characteristics of chitosan based films (i.e. polymer “bubbles”, “fingertips” and “sponge-like” structures). These structures were investigated by scanning electron microscopy and atomic force microscopy. The morphology of the structures obtained was correlated with the response of oligodendrocytes cells line. In vitro tests on the patterned surface showed that early cell growth was conditioned by the microtopography and indicate possible uses of the structures in biomedical applications.

Stress mapping on the porous silicon microcapsules by Raman microscopy

► The intrinsic stresses have a great importance in the poly-Si technology. ► Microcapsules are promising structures in biomedical applications. ► Raman technique is non-destructive and has high sensitivity for stress measurements. ► The compositional Raman mapping of crystal phases of microcapsule was done. ► The maximum stress at a level 1.74 GPa was found on the sides of microcapsule. Silicon micromachined microcapsules have recently been used in biomedical applications as individual in sensing and drug delivery systems due to its biocompatibility and biodegradability properties. Microcapsules micromachining process is quite a complex procedure and to develop a high outcome the process has to be well controlled. One of the important physical characteristics influencing degradation of the microcapsules during the micromachining is a mechanical stresses in the microcapsules. In this work we investigated the stress in polysilicon microcapsules and their crystallinity before and after electrochemical etching process by means of micro-Raman spectroscopy and atomic force microscopy. It was shown that microcapsules fabrication process leads to the appearance of strong mechanical stress (up to 1.74 GPa), at the edges of produced microcapsules which can damage the structures. The combined AFM and Raman investigations confirm the presence of silicon amorphous phase after technological process and allow the stress mapping. We demonstrate a great potential of Raman stress imaging to be used for the testing of silicon microstructures and an improvement of fabrication process.

Nanoengineering life: from cell to tissue

Nanoengineering, which brings several traditional disciplines including physics, engineering, biology and medicine together, is an emerging tool for manipulating major constituents of living organisms such as cells and tissues. Generally, the scopes of nanoengineering techniques include

Nucleic acid-based nanoengineering: novel structures for biomedical applications.

Nanoengineering exploits the interactions of materials at the nanometre scale to create functional nanostructures. It relies on the precise organization of nanomaterials to achieve unique functionality. There are no interactions more elegant than those governing nucleic acids via Watson-Crick base-pairing rules. The infinite combinations of DNA/RNA base pairs and their remarkable molecular recognition capability can give rise to interesting nanostructures that are only limited by our imagination. Over the past years, creative assembly of nucleic acids has fashioned a plethora of two-dimensional and three-dimensional nanostructures with precisely controlled size, shape and spatial functionalization. These nanostructures have been precisely patterned with molecules, proteins and gold nanoparticles for the observation of chemical reactions at the single molecule level, activation of enzymatic cascade and novel modality of photonic detection, respectively. Recently, they have also been engineered to encapsulate and release bioactive agents in a stimulus-responsive manner for therapeutic applications. The future of nucleic acid-based nanoengineering is bright and exciting. In this review, we will discuss the strategies to control the assembly of nucleic acids and highlight the recent efforts to build functional nucleic acid nanodevices for nanomedicine.

Fabrication and compressive properties of Ti6Al4V implant with honeycomb‐like structure for biomedical applications

PurposeThe purpose of this paper is to verify the feasibility and evaluate the compressive properties of Ti6Al4V implants with controlled porosity via electron beam melting process. This process might be a promising method to fabricate orthopedic implants with suitable pore architecture and matched mechanical properties.Design/methodology/approachTi6Al4V implants with controlled porosity are produced using an electron beam melting machine. A scanning electron microscope is utilized to examine the macro‐pore structures of the Ti6Al4V implants. The compressive test is performed to investigate the mechanical properties of the porous implants.FindingsThe fabricated samples show a fully interconnected open‐pore network. The compressive yield strength of the Ti6Al4V implants with the porosity of around 51 percent is higher than that of human cortical bone. The Young's modulus of the implants is similar to that of cortical bone.Research limitations/implicationsThe surface of samples produced by electron beam melting process is covered with loosely spherical metal particles. Polishing and ultrasonic cleaning have to be used to remove the loose remnants.Originality/valueThis paper presents the potential application in the fabrication of orthopedic or dental implants using electron beam melting process.

Complex Microstructured 3D Surfaces Using Chitosan Biopolymer

A technique for producing micrometer-scale structures over large, nonplanar chitosan surfaces is described. The technique makes use of the rheological characteristics (deformability) of the chitosan to create freestanding, three-dimensional scaffolds with controlled shapes, incorporating defined microtopography. The results of an investigation into the technical limits of molding different combinations of shapes and microtopographies are presented, highlighting the versatility of the technique when used irrespectively with inorganic or delicate organic moulds. The final, replicated scaffolds presented here are patterned with arrays of one-micrometer-tall microstructures over large areas. Structural integrity is characterized by the measurement of structural degradation. Human umbilical vein endothelial cells cultured on a tubular scaffold show that early cell growth is conditioned by the microtopography and indicate possible uses for the structures in biomedical applications. For those applications requiring improved chemical and mechanical resistance, the structures can be replicated in poly(dimethyl siloxane).