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BackgroundOrthodontic brackets provide a favorable environment forStreptococcus mutansbiofilm formation, increasing the risk of white spots and dental caries. Manganese oxide (MnO2) nanozyme-doped diatom microbubbler (DM) is a recently developed material for biofilm removal. DM can generate oxygen by catalase-mimicking activity in Hydrogen peroxide (H2O2) solution and move with ejecting oxygen microbubbles to produce a mechanical self-cleansing effect. This study aimed to evaluate the feasibility of DM as a novel bracket cleaner.MethodsDM was prepared according to the protocol and analyzed using a scanning electron microscope (SEM). We treatedS. mutansbiofilms grown over bracket with phosphate-buffered saline (PBS group), 0.12% chlorhexidine (CHX group), 3% H2O2(H2O2group), and co-treatment with 3 mg/mL of DM and 3% H2O2(DM group). The biofilm removal effect was analyzed using crystal violet assay, and the results were observed using SEM. The viability ofS. mutansin remaining biofilms was evaluated using confocal laser scanning microscopy (CLSM). Finally, we examined the effect of all materials on mature multispecies biofilms formed on debonded brackets.ResultsCrystal violet assay results revealed that the CHX group removed more biofilms than the control group, and the DM group removed biofilms more effectively than the CHX group (p S. mutansbut failed to remove most biofilms on brackets. However, DM effectively removed biofilms and mature multispecies biofilms on debonded brackets (p ConclusionsCo-treatment with DM and H2O2is effective in removing biofilms on orthodontic brackets compared to conventional antibacterial agents.

A combination of techniques from 3D printing, tissue engineering and biomaterials has yielded a new class of engineered biological robots that could be reliably controlled via applied signals. These machines are powered by a muscle strip composed of differentiated skeletal myofibers in a matrix of natural proteins, including fibrin, that provide physical support and cues to the cells as an engineered basement membrane. However, maintaining consistent results becomes challenging when sustaining a living system in vitro. Skeletal muscle must be preserved in a differentiated state and the system is subject to degradation by proteolytic enzymes that can break down its mechanical integrity. Here we examine the life expectancy, breakdown, and device failure of engineered skeletal muscle bio-bots as a result of degradation by three classes of proteases: plasmin, cathepsin L, and matrix metalloproteinases (MMP-2 and MMP-9). We also demonstrate the use of gelatin zymography to determine the effects of differentiation and inhibitor concentration on protease expression. With this knowledge, we are poised to design the next generation of complex biological machines with controllable function, specific life expectancy and greater consistency. These results could also prove useful for the study of disease-specific models, treatments of myopathies, and other tissue engineering applications.

A complex and functional living cellular system requires the interaction of one or more cell types to perform specific tasks, such as sensing, processing, or force production. Modular and flexible platforms for fabrication of such multi-cellular modules and their characterization have been lacking. Here, we present a modular cellular system, made up of multi-layered tissue rings containing integrated skeletal muscle and motor neurons (MNs) embedded in an extracellular matrix. The MNs were differentiated from mouse embryonic stem cells through the formation of embryoid bodies (EBs), which are spherical aggregations of cells grown in a suspension culture. The EBs were integrated into a tissue ring with skeletal muscle, which was differentiated in parallel, to create a co-culture amenable to both cell types. The multi-layered rings were then sequentially placed on a stationary three-dimensional-printed hydrogel structure resembling an anatomical muscle–tendon–bone organization. We demonstrate that the site-specific innervation of a group of muscle fibers in the multi-layered tissue rings allows for muscle contraction via chemical stimulation of MNs with glutamate, a major excitatory neurotransmitter in the mammalian nervous system, with the frequency of contraction increasing with glutamate concentration. The addition of tubocurarine chloride (a nicotinic receptor antagonist) halted the contractions, indicating that muscle contraction was MN induced. With a bio-fabricated system permitting controllable mechanical and geometric attributes in a range of length scales, our novel engineered cellular system can be utilized for easier integration of other modular “building blocks” in living cellular and biological machines.

Low-cost detection of pathogens and biomolecules at the point-of-care promises to revolutionize medicine through more individualized monitoring and increased accessibility to diagnostics in remote and resource-limited areas. While many approaches to biosensing are still limited by expensive components or inadequate portability, we present here an ELISA-inspired lab-on-a-chip strategy for biological detection based on liposome tagging and ion-release impedance spectroscopy. Ion-encapsulating dipalmitoylphosphatidylcholine (DPPC) liposomes can be functionalized with antibodies and are stable in deionized water yet permeabilized for ion release upon heating, making them ideal reporters for electrical biosensing of surface-immobilized antigens. We demonstrate the quantification of these liposomes by real-time impedance measurements, as well as the qualitative detection of viruses as a proof-of-concept toward a portable platform for viral load determination which can be applied broadly to the detection of pathogens and other biomolecules.

Multifunctional particles with distinct physiochemical phases are required by a variety of applications in biomedical engineering, such as diagnostic imaging and targeted drug delivery. This motivates the development of a repeatable, efficient, and customizable approach to manufacturing particles with spatially segregated bioactive moieties. This study demonstrates a stereolithographic 3D printing approach for designing and fabricating large arrays of biphasic poly (ethylene glycol) diacrylate (PEGDA) gel particles. The fabrication parameters governing the physical and biochemical properties of multi-layered particles are thoroughly investigated, yielding a readily tunable approach to manufacturing customizable arrays of multifunctional particles. The advantage in spatially organizing functional epitopes is examined by loading superparamagnetic iron oxide nanoparticles (SPIONs) and bovine serum albumin (BSA) in separate layers of biphasic PEGDA gel particles and examining SPION-induced magnetic resonance (MR) contrast and BSA-release kinetics. Particles with spatial segregation of functional moieties have demonstrably higher MR contrast and BSA release. Overall, this study will contribute significant knowledge to the preparation of multifunctional particles for use as biomedical tools.

Biological cells are major building blocks of tissues and organs of living organisms. These cells are also being used as biomarkers for diagnosis and sources for regenerative medicine. To better understand and even regulate diverse activities of cells, materials capable of interacting with cells have been designed by integrating various material chemistry, characterization, and processing techniques. These materials are often integrated with various nano- and microscale engineering devices. In this article, we provide an overview of materials for biological modulation, sensing, and imaging and also discuss opportunities for the future development of multifunctional materials for sensing and therapies.

To attain the effective local and sustained delivery of plasmid DNA (pDNA) encoding for a growth factor.We hypothesized that controlling the degradation rate of biomaterials encapsulating pDNA via concurrent physical dissociation of the cross-linked structure and hydrolytic chain breakage of polymers would allow one to significantly broaden the range of pDNA release rate. This hypothesis was examined using ionically cross-linked polysaccharide hydrogels which were previously designed to rapidly degrade via engineering of ionic cross-linking junction and partial oxidation of polysaccharide chains.The hydrogel degradation rates were varied over the broad range, and pDNA release correlated with the gel degradation rate. Degradable hydrogels were used for the local and sustained delivery of a pDNA encoding for vascular endothelial growth factor (VEGF) in the ischemic hindlimbs of mice, and local pDNA release significantly improved the recovery of blood perfusion as compared with a bolus injection of VEGFencoding pDNA.This strategy to control the hydrogel degradation rate may be useful in regulating the delivery of a broad array of macromolecular drugs, and subsequently improve their therapeutic efficacy.

Non-viral gene vectors are commonly used for gene therapy1,2,3 owing to safety concerns with viral vectors4. However, non-viral vectors are plagued by low levels of gene transfection and cellular expression1,2. Current efforts to improve the efficiency of non-viral gene delivery are focused on manipulations of the delivery vector5,6,7,8,9,10,11,12, whereas the influence of the cellular environment in DNA uptake is often ignored. The mechanical properties (for example, rigidity) of the substrate to which a cell adheres have been found to mediate many aspects of cell function including proliferation, migration and differentiation13,14,15,16,17, and this suggests that the mechanics of the adhesion substrate may regulate a cell's ability to uptake exogeneous signalling molecules. In this report, we present a critical role for the rigidity of the cell adhesion substrate on the level of gene transfer and expression. The mechanism relates to material control over cell proliferation, and was investigated using a fluorescent resonance energy transfer (FRET) technique18,19,20,21. This study provides a new material-based control point for non-viral gene therapy.

Refined control over the mechanical properties of hydrogels formed from cross-linking of polymers is increasingly regarded as critical for their successful application. In general, increasing the cross-linking density (ρ) of polymer gels raises the mechanical rigidity, but makes the gels more brittle. We proposed that controlling properties of the cross-linking junction and the cross-linking type would mediate the fracture response of the gels, and allow one to decouple the dependency of the mechanical stiffness and toughness from ρ of the gel. This possibility was investigated with alginate hydrogels, because alginate can be gelled via ionic or covalent cross-linking. Increasing ρ of the gels formed using covalent cross-linking with adipic acid dihydrazide or poly (acrylamide-co-hydrazide) raised the elastic modulus (E), but led to a reduction in the toughness of the gels. In contrast, increasing the number of calcium cross-links slowed the crack opening of the gels, and subsequently raised both E and work to fracture (W). From the results of this study, we could demonstrate a novel approach to regulate different mechanical properties of gels in an independent manner. This study provides a valuable guideline to the design of a broad array of polymer hydrogels.

The mechanical properties of alginate hydrogels are critical to their successful use in tissue engineering. We hypothesized that combining alginates of differing molecular weights would allow one to readily control and decouple the viscosity of the pre-gel solution from the post-gel stiffness. To test this, binary hydrogels were prepared by incorporating low molecular weight (MW) alginate (Mn ~ 3.3 x 104 g/mol) into 1 %(w/w) alginate solutions composed of high MW alginate (Mn ~ 2.2 x 105 g/mol). The addition of low MW alginate had minimal effects on the solution viscosity, allowing high solids loading in the solution while maintaining a workable solution. However, the increased mass loading resulted in much higher stiffness gels following ionic cross-linking with calcium. These data may be interpreted in relation to the microstructure of the solution versus hydrogel.