Laser printing of microbial systems: effect of absorbing metal film

3D bioprinting of microorganisms: principles and applications

In recent years, the ability to create intricate, live tissues and organs has been made possible thanks to three-dimensional (3D) bioprinting. Although tissue engineering has received a lot of attention, there is growing interest in the use of 3D bioprinting for microorganisms. Microorganisms like bacteria, fungi, and algae, are essential to many industrial bioprocesses, such as bioremediation as well as the manufacture of chemicals, biomaterials, and pharmaceuticals. This review covers current developments in 3D bioprinting methods for microorganisms. We go over the bioink compositions designed to promote microbial viability and growth, taking into account factors like nutrient delivery, oxygen supply, and waste elimination. Additionally, we investigate the most important bioprinting techniques, including extrusion-based, inkjet, and laser-assisted approaches, as well as their suitability with various kinds of microorganisms. We also investigate the possible applications of 3D bioprinted microbes. These range from constructing synthetic microbial consortia for improved metabolic pathway combinations to designing spatially patterned microbial communities for enhanced bioremediation and bioprocessing. We also look at the potential for 3D bioprinting to advance microbial research, including the creation of defined microenvironments to observe microbial behavior. In conclusion, the 3D bioprinting of microorganisms marks a paradigm leap in microbial bioprocess engineering and has the potential to transform many application areas. The ability to design the spatial arrangement of various microorganisms in functional structures offers unprecedented possibilities and ultimately will drive innovation.

Laser Bioprinting with Cell Spheroids: Accurate and Gentle

Laser printing with cell spheroids can become a promising approach in tissue engineering and regenerative medicine. However, the use of standard laser bioprinters for this purpose is not optimal as they are optimized for transferring smaller objects, such as cells and microorganisms. The use of standard laser systems and protocols for the transfer of cell spheroids leads either to their destruction or to a significant deterioration in the quality of bioprinting. The possibilities of cell spheroids printing by laser-induced forward transfer in a gentle mode, which ensures good cell survival ~80% without damage and burns, were demonstrated. The proposed method showed a high spatial resolution of laser printing of cell spheroid geometric structures at the level of 62 ± 33 µm, which is significantly less than the size of the cell spheroid itself. The experiments were performed on a laboratory laser bioprinter with a sterile zone, which was supplemented with a new optical part based on the Pi-Shaper element, which allows for forming laser spots with different non-Gaussian intensity distributions. It is shown that laser spots with an intensity distribution profile of the "Two rings" type (close to Π-shaped) and a size comparable to a spheroid are optimal. To select the operating parameters of laser exposure, spheroid phantoms made of a photocurable resin and spheroids made from human umbilical cord mesenchymal stromal cells were used.

Laser-assisted bioprinting of microorganisms with hydrogel microdroplets: peculiarities of Ascomycota and Basidiomycota yeast transfer

Laser-assisted bioprinting of microbial cells by hydrogel microdroplets is a rapidly developing and promising field that can contribute to solving a number of issues in microbiology and biotechnology. To date, most research on the use of laser bioprinting for microorganism manipulation and sorting has focused on prokaryotes; the bioprinting of eukaryotic microorganisms is much less understood. The use of hydrogel allows solving two fundamental problems: creating comfortable environments for living microorganisms and imparting the necessary rheological properties of the gel for the stable transfer of microdroplets of a preset size. Two main problems were solved in this article. First, the parameters of the hydrogel based on hyaluronic acid and laser fluence to ensure stable transfer of single drops are selected. Second, possible differences in the bioprinting by hyaluronic acid hydrogel microdroplets with yeasts of various taxonomy (Ascomycota vs Basidiomycota), which form and do not form polysaccharide capsules and evaluated. We have performed laser induced forward transfer of 8 yeast species (Goffeauzyma gilvescens, Lipomyces lipofer, Lipomyces starkey, Pichia manshurica, Saitozyma podzolica, Schwanniomyces occidentalis var. occidentalis, Sterigmatosporidium polymorphum, Vanrija humicola) and assessed its viability based on colony formation on the nutrient medium. It is shown that after laser-induced transfer in hydrogel microdroplets the mean viability rate was 77% with some strains showing relatively high viability rates exceeding 90%. Effect of capsules presence on colony formation after laser bioprinting was not revealed. Differences in laser transfer of the yeast of various phyla were found-basidiomycetes formed a greater number of colonies than ascomycetes. The causes and mechanisms of these effects require detailed studies. The data obtained contributes to the knowledge about the bioprinting of eukaryotic microorganisms and can be useful in the studies of single microbial cells and inter-organism interactions.

Fabrication of periodic microscale stripes of silver by laser interference induced forward transfer and their SERS properties

The micro-stripe structure was prepared by laser interference induced forward transfer technique, composed of Ag nano-particles (NPs). The effects of the film thickness with the carbon nano-particles mixed polyimide (CNPs@PI), Ag film thickness, and laser fluence were studied on the transferred micro-stripe structure. The periodic Ag micro-stripe with good resolution was obtained in a wide range of CNPs@PI film thickness from ∼0.5 to ∼1.0μm for the Ag thin film ∼20 nm. The distribution of the Ag NPs composing the micro-stripe was compact. Nevertheless, the average size of the transferred Ag NPs was increased from ∼41 to ∼197 nm with the change of the Ag donor film from ∼10 to ∼40 nm. With the increase of the laser fluence from 102 to 306 mJ·cm^-2per-beam, the transferred Ag NPs became aggregative, improving the resolution of the corresponding micro-stripe. Finally, the transferred Ag micro-stripe exhibited the significant surface enhanced Raman scattering (SERS) property for rhodamine B (RhB). While the concentration of the RhB reached 10^-10mol·L^-1, the Raman characteristic peaks of the RhB were still observed clearly at 622, 1359 and 1649 cm^-1. These results indicate that the transferred Ag micro-stripe has potential application as a SERS chip in drug and food detection.

Metal Nanoparticles in Laser Bioprinting

Laser bioprinting is a promising method for applications in biotechnology, tissue engineering, and regenerative medicine. It is based on a microdroplet transfer from a donor slide induced by laser pulse heating of a thin metal absorption film covered with a layer of hydrogel containing living cells (bioink). Due to the presence of the metal absorption layer, some debris in the form of metal nanoparticles is printed together with bioink microdroplets. In this article, experimental investigations of the amount of metal nanoparticles formed during the laser bioprinting process and transported in bioink microdroplets are performed. As metal absorption layers, Ti films with the thickness in the range of 25-400 nm, produced by magnetron spattering, were applied. Dependences of the volume of bioink microdroplets and the amount of Ti nanoparticles within them on the laser pulse fluence were obtained. It has been experimentally found that practically all nanoparticles remain in the hydrogel layer on the donor slide during bioprinting, with only a small fraction of them transferred within the microdroplet (0.5% to 2.5%). These results are very important for applications of laser bioprinting since the transferred metal nanoparticles can potentially affect living systems. The good news is that the amount of such nanoparticles is very low to produce any negative effect on the printed cells.

Projection Microstereolithographic Microbial Bioprinting for Engineered Biofilms

Microbes are critical drivers of all ecosystems and many biogeochemical processes, yet little is known about how the three-dimensional (3D) organization of these dynamic organisms contributes to their overall function. To probe how biofilm structure affects microbial activity, we developed a technique for patterning microbes in 3D geometries using projection stereolithography to bioprint microbes within hydrogel architectures. Bacteria were printed and monitored for biomass accumulation, demonstrating postprint viability of cells using this technique. We verified our ability to integrate biological and geometric complexity by fabricating a printed biofilm with two E. coli strains expressing different fluorescence. Finally, we examined the target application of microbial absorption of metal ions to investigate geometric effects on both the metal sequestration efficiency and the uranium sensing capability of patterned engineered Caulobacter crescentus strains. This work represents the first demonstration of the stereolithographic printing of microbials and presents opportunities for future work of engineered biofilms and other complex 3D structured cultures.

Laser-induced Forward Transfer Hydrogel Printing: A Defined Route for Highly Controlled Process

Laser-induced forward transfer is a versatile, non-contact, and nozzle-free printing technique which has demonstrated high potential for different printing applications with high resolution. In this article, three most widely used hydrogels in bioprinting (2% hyaluronic acid sodium salt, 1% methylcellulose, and 1% sodium alginate) were used to study laser printing processes. For this purpose, the authors applied a laser system based on a pulsed infrared laser (1064 nm wavelength, 8 ns pulse duration, 1 – 5 J/cm² laser fluence, and 30 μm laser spot size). A high-speed shooting showed that the increase in fluence caused a sequential change in the transfer regimes: No transfer regime, optimal jetting regime with a single droplet transfer, high speed regime, turbulent regime, and plume regime. It was demonstrated that in the optimal jetting regime, which led to printing with single droplets, the size and volume of droplets transferred to the acceptor slide increased almost linearly with the increase of laser fluence. It was also shown that the maintenance of a stable temperature (±2°C) allowed for neglecting the temperature-induced viscosity change of hydrogels. It was determined that under room conditions (20°C, humidity 50%), the hydrogel layer, due to drying processes, decreased with a speed of about 8 μm/min, which could lead to a temporal variation of the transfer process parameters. The authors developed a practical algorithm that allowed quick configuration of the laser printing process on an applied experimental setup. The configuration is provided by the change of the easily tunable parameters: Laser pulse energy, laser spot size, the distance between the donor ribbon and acceptor plate, as well as the thickness of the hydrogel layer on the donor ribbon slide.

Tepidiforma bonchosmolovskayae gen. nov., sp. nov., a moderately thermophilic Chloroflexi bacterium from a Chukotka hot spring (Arctic, Russia), representing a novel class, Tepidiformia, which includes the previously uncultivated lineage OLB14

A novel aerobic moderately thermophilic bacterium, strain 3753O^T, was isolated from a Chukotka hot spring (Arctic, Russia) using the newly developed technology of laser engineering of microbial systems. Сells were regular short rods, 0.4×0.8-2.0 µm in size, with a monoderm-type envelope and a single flagellum. The temperature and pH ranges for growth were 42-60 °C and pH 6.5-8.5, the optima being 50-54 °C and pH 7.3. Strain 3753O^T grew chemoorganoheterotrophically on a number of carbohydrates or peptidic substrates and volatile fatty acids, and chemolithoautotrophically with siderite (FeCO₃) as the electron donor. The major cellular fatty acid was branched C_19 : 0. Phosphatidylethanolamine, phosphatidylglycerol and two unidentified phospholipids as well as two yellow carotenoid-type pigments were detected in the polar lipid extract. Strain 3753O^T was inhibited by chloramphenicol, polymyxin B, vancomycin, streptomycin, neomycin and kanamycin, but resistant to the action of novobiocin and ampicillin. The DNA G+C content was 69.9 mol%. The 16S rRNA gene as well as 51 conservative protein sequence-based phylogenetic analyses placed strain 3753O^T within the previously uncultivated lineage OLB14 in the phylum Chloroflexi. Taking into account the phylogenetic position as well as phenotypic properties of the novel isolate, the novel genus and species Tepidiforma bonchosmolovskayae gen. nov., sp. nov., within the Tepidiformaceae fam. nov., the Tepidiformales ord. nov. and the Tepidiformia classis nov. are proposed. The type strain of Tepidiforma bonchosmolovskayae is 3753O^T (=VKM B-3389^T=KTCT 72284^T).

New microorganism isolation techniques with emphasis on laser printing

The study of biodiversity, growth, development, and metabolism of cultivated microorganisms is an integral part of modern microbiological, biotechnological, and medical research. Such studies require the development of new methods of isolation, cultivation, manipulation, and study of individual bacterial cells and their consortia. To this end, in recent years, there has been an active development of different isolation and three-dimensional cell positioning methods. In this review, the optical tweezers, surface heterogeneous functionalization, multiphoton lithography, microfluidic techniques, and laser printing are reviewed. Laser printing is considered as one of the most promising techniques and is discussed in detail.