Mechanical Feedback Control for Multicellular Tissue Size Maintenance: A Minireview

All living tissues and organs have their respective sizes, critical to various biological functions, such as development, growth, and homeostasis. As tissues and organs generally converge to a certain size, intrinsic regulatory mechanisms may be involved in the maintenance of size regulation. In recent years, important findings regarding size regulation have been obtained from diverse disciplines at the molecular and cellular levels. Here, I briefly review the size regulation of biological tissues from the perspective of control systems. This minireview focuses on how feedback systems engage in tissue size maintenance through the mechanical interactions of constituent cell collectives through intracellular signaling. I introduce a general framework of a feedback control system for tissue size regulation, followed by two examples: maintenance of epithelial tissue volume and epithelial tube diameter. The examples deliver the idea of how cellular mechano-response works for maintaining tissue size.

Modulation of the electrical double layer in metals and conducting polymers

The electrical double layer (EDL) formed at the interface between various materials and an electrolyte has been studied for a long time. In particular, the EDL formed at metal/electrolyte interfaces is central in electrochemistry, with a plethora of applications ranging from corrosion to batteries to sensors. The discovery of highly conductive conjugated polymers has opened a new area of electronics, involving solution-based or solution-interfaced devices, and in particular in bioelectronics, namely for use in deep-brain stimulation electrodes and devices to measure and condition cells activity, as these materials offer new opportunities to interface cells and living tissues. Here, it is shown that the potential associated to the double layer formed at the interface between either metals or conducting polymers and electrolytes is modified by the application of an electric field along the conductive substrate. The EDL acts as a transducer of the electric field applied to the conductive substrate. This observation has profound implications in the modelling and operation of devices relying on interfaces between conductive materials (metals and conjugated polymers) and electrolytes, which encompasses various application fields ranging from medicine to electronics.

Organochlorine Compounds in Beached Plastics and Marine Organisms

Here we compare bioaccumulation factors in marine organisms to partition ratios in marine debris for dichlorodiphenyltrichloroethane and polychlorinated biphenyls. Both organochlorines are synthetic persistent organic pollutants emitted into the environment since the beginning of the last century in approximately equal amounts. Their vast use and dispersion have resulted in approximately similar median concentrations of the two organochlorines in some pelagic organisms, namely in the liver and muscle tissue of fish. Molluscs, on the other hand, show higher median uptake of PCBs (median = 2.34 ng/g) than of DDTs (median = 1.70 ng/g), probably reflecting more localized conditions. We found that the bioaccumulation factors can be several orders of magnitude higher than the partition ratios. For instance, the median concentrations of organochlorines in the different matrices of fish, birds, and mammals are between one to four orders of magnitude higher than those found in marine debris, when lipid-normalized; or up to two orders of magnitude when measured as wet-weight. But, in molluscs, bioaccumulation/partition equals unity, which agrees with previous studies using passive samplers. Future research should focus on reducing sources of uncertainty by 1) homogenization of chemical procedures; 2) better assessment of chemical partition equilibrium between water and polymers in environmental conditions; 3) use of (multi)polymer passive samplers better aimed at mimicking uptake of specific living tissues.

Raman Signal Denoising Using Fully Convolutional Encoder Decoder Network

Raman spectroscopy is a vibrational method that gives molecular information rapidly and non-invasively. Despite its advantages, the weak intensity of Raman spectroscopy leads to low-quality signals, particularly with tissue samples. The requirement of high exposure times makes Raman a time-consuming process and diminishes its non-invasive property while studying living tissues. Novel denoising techniques using convolutional neural networks (CNN) have achieved remarkable results in image processing. Here, we propose a similar approach for noise reduction for the Raman spectra acquired with 10x lower exposure times. In this work, we developed fully convolutional encoder-decoder architecture (FCED) and trained them with noisy Raman signals. The results demonstrate that our model is superior (p-value <0.0001) to the conventional denoising techniques such as the Savitzky-Golay filter and wavelet denoising. Improvement in the signal-to-noise ratio values ranges from 20% to 80%, depending on the initial signal-to-noise ratio. Thus, we proved that tissue analysis could be done in a shorter time without any need for instrumental enhancement.

Soft-Tissue-Mimicking Using Hydrogels for the Development of Phantoms

With the currently available materials and technologies it is difficult to mimic the mechanical properties of soft living tissues. Additionally, another significant problem is the lack of information about the mechanical properties of these tissues. Alternatively, the use of phantoms offers a promising solution to simulate biological bodies. For this reason, to advance in the state-of-the-art a wide range of organs (e.g., liver, heart, kidney as well as brain) and hydrogels (e.g., agarose, polyvinyl alcohol –PVA–, Phytagel –PHY– and methacrylate gelatine –GelMA–) were tested regarding their mechanical properties. For that, viscoelastic behavior, hardness, as well as a non-linear elastic mechanical response were measured. It was seen that there was a significant difference among the results for the different mentioned soft tissues. Some of them appear to be more elastic than viscous as well as being softer or harder. With all this information in mind, a correlation between the mechanical properties of the organs and the different materials was performed. The next conclusions were drawn: (1) to mimic the liver, the best material is 1% wt agarose; (2) to mimic the heart, the best material is 2% wt agarose; (3) to mimic the kidney, the best material is 4% wt GelMA; and (4) to mimic the brain, the best materials are 4% wt GelMA and 1% wt agarose. Neither PVA nor PHY was selected to mimic any of the studied tissues.

Laser-Induced Thermal Treatment of Superficial Human Tumors: An Advanced Heating Strategy and Non-Arrhenius Law for Living Tissues

The most interesting, but insufficiently known results obtained by the author in modeling laser-induced hyperthermia of human tumors are discussed. It is important that the traditional equation for the local bio-heat transfer does not work in superficial layers of the body. It is shown also that the classical Arrhenius law is not applicable to living tissues because of the tissue regeneration due to oxygen supplied by the arterial blood. The latter is one of the main reasons of the suggested strategy of laser heating of tumors in the therapeutic window of semitransparency when the tumor asphyxiation is considered as one of important weapons against the cancer. The other advantages of this advanced strategy of a soft thermal treatment (in few of sessions), which is painless for patients, are discussed as well. Some features of modeling various heat transfer modes are also considered. The best choice between the simplest differential models for the radiative transfer calculations is dependent of the particular problem statement. The known finite-difference or finite element algorithms can be preferable in solving transient heat transfer problems. As a rule, it depends on the shape of the computational region. It is expected that this paper will help the colleagues to overcome some typical weaknesses of computational modeling of infrared photothermal treatment of superficial tumors.

Reversable deformation of artificial cell colony for muscle behavior mimicry triggered by actin polymerization

The mimicry of living tissues from artificial cells is beneficial to understanding the interaction mechanism among cells, as well as holding great potentials in the tissue engineering field. Self-powered artificial cells capable of reversible deformation are developed by encapsulating living mitochondria, actin proteins, and methylcellulose. Upon the addition of pyruvate molecules, the mitochondria produce ATP molecules as energy sources to trigger the polymerization of actin. ATP molecules were produced by mitochondria (2.76×1010/ml) with the concentrations of 35.8±3.2 µ M, 158.2±19.3 µ M and 200.7±20.1 µ M by adding pyruvate molecules with the concentration of 3 µ M; 12 µ M and 21 µ M, respectively. The reversible deformation of artificial cells is experienced with spindle shape resulting from the polymerization of actins to form filaments adjacent to the lipid bilayer, subsequently back to spherical shape resulting from the depolymerization of actin filaments upon laser irradiations. The linear colonies composed of these artificial cells exhibit collective contraction and relaxation behavior to mimic muscle tissues. At the stage of maximum contraction, the long axis of each GUV is in parallel to each other. All colonies are synchronized in the contraction phase. The deformation of each GUV in the colonies is influenced by its adjacent GUVs. The muscle-like artificial cell colonies paved the path to develop sustainably self-powered artificial tissues in the field of tissue engineering.

Major advances in minimally traumatic surgery in implantodontics: the concise systematic review

Introduction: Dental implant procedures have reached about one million dental implants per year in the world. In this context, it is necessary to establish the state of the art of minimally traumatic procedures for dental implants, especially after bone graft procedures and/or the use of biomaterials for bone elevation. In this context of optimizing techniques for better management of dental implants, faster and more accurate methods were developed by dentists, with post-operative results with better results and quality of life, through minimally invasive procedures. Objective: To carry out a concise systematic review of minimally traumatic surgery for dental implants, as well as to elucidate the main techniques for this. Methods: The rules of the Systematic Review Platform-PRISMA were followed. The survey was conducted from July 2021 to October 2021 and was developed based on Scopus, PubMed, Science Direct, Scielo, and Google Scholar. Study quality was based on the GRADE instrument and the risk of bias was analyzed according to the Cochrane instrument. Results: Since the most primordial extraction techniques were created and developed, several attempts have been made to minimize the professional's effort, reduce surgical time and alleviate bleeding and inflammatory processes, edema, pain, and ecchymosis that can affect patients, in the trans and postoperative periods. Thus, the maximum preservation of the integrity of the soft tissues (papillae and free and inserted gingival band) adjacent to the prosthetic spaces should be sought; preservation of the alveolar bone ridge level. Based on the histological concept in which living tissues are formed by cells joined by thin elastic tissue and with nerve fibrils, capillaries, lymphatic and blood vessels. The disruption of these cells by surgical trauma provides the release of enzymes that delay healing. For this reason, surgical trauma should be minimized. Conclusion: There are many attempts to minimize the professional effort, reduce surgical time and alleviate bleeding and inflammatory processes, edema, pain, and ecchymosis that can affect patients. Thus, the maximum preservation of the integrity of the soft tissues adjacent to the prosthetic spaces and the preservation of the level of the ridge of the alveolar bone to achieve a minimization of surgical trauma must be sought.

The double-edged role of nitric oxide drives predictable microbial community organization according to the microenvironment

Microbial assemblages are omnipresent in the biosphere, forming communities on the surfaces of roots, rocks, and within living tissues. These communities can exhibit strikingly beautiful compositional structures, with certain members reproducibly occupying particular spatiotemporal microniches. Yet often, we lack the ability to explain the spatial patterns we see within them. To test the hypothesis that certain spatial patterns in microbial communities may be explained by the exchange of redox-active metabolites whose biological function is sensitive to environmental gradients, here we developed a simple community consisting of synthetic Pseudomonas aeruginosa strains with a partitioned denitrification pathway: a strict consumer and strict producer of nitric oxide (NO), a key pathway intermediate. Because NO can be both toxic or beneficial depending on the amount of oxygen present, this system provided an opportunity to investigate whether dynamic oxygen gradients can tune metabolic cross-feeding in a predictable fashion. Using a combination of genetic analysis, different growth environments and imaging, we show that oxygen availability controls whether NO cross-feeding is commensal or mutually beneficial, and that this organizing principle maps to the microscale. More generally, this work underscores the importance of considering the double-edged roles redox-active metabolites can play in shaping microbial communities.

3D bioprinting: current status and trends—a guide to the literature and industrial practice

The multidisciplinary research field of bioprinting combines additive manufacturing, biology and material sciences to create bioconstructs with three-dimensional architectures mimicking natural living tissues. The high interest in the possibility of reproducing biological tissues and organs is further boosted by the ever-increasing need for personalized medicine, thus allowing bioprinting to establish itself in the field of biomedical research, and attracting extensive research efforts from companies, universities, and research institutes alike. In this context, this paper proposes a scientometric analysis and critical review of the current literature and the industrial landscape of bioprinting to provide a clear overview of its fast-changing and complex position. The scientific literature and patenting results for 2000–2020 are reviewed and critically analyzed by retrieving 9314 scientific papers and 309 international patents in order to draw a picture of the scientific and industrial landscape in terms of top research countries, institutions, journals, authors and topics, and identifying the technology hubs worldwide. This review paper thus offers a guide to researchers interested in this field or to those who simply want to understand the emerging trends in additive manufacturing and 3D bioprinting. Graphic abstract