With the important role of 3D printing in medical biology research, scientists have created new bio-3D printing ink and developed progressive microfluidic technology. Recently, University of Glasgow has studied the bacteria loaded microgels as an autonomous 3D environment for stem cell engineering. In this study, a one-step microfluidic system was developed. The system can encapsulate stem cells and genetically engineered non pathogenic bacteria in the so-called 3D pearl lace alginate microgel with high level of monodispersity and cell viability. Power.

In research, although most technologies rely on droplet extrusion, researchers are creating more efficient systems through one-step droplet microfluidics. The preparation of pearlite tape microgels occurs under physiological pH without any sheath material. Channel size and overall design mean avoiding cell shear stress and promoting vitality.

The gel constructs are unique, with spacer units in a single microcapsule and connectivity found in fibrous constructs. Furthermore, the spacing of the cells and the connection between them are highly adjustable, resulting in a highly monodisperse pearl-lace interconnection structure. Related to manufacturing processes, pearl cells benefit from slower crosslinking in addition to suppressed shear stress compared with interconnection units. The technology allows the manufacture of cell-carrying hydrogels with unprecedented precision and control, which have been used as low-cost 3D bioprinting prototypes.

(Droplet-based microfluidic settings)

(A) The schematic diagram of the microfluidic device and the encapsulation of prokaryotic and eukaryotic cells.
(B) Image of capillary-based microfluidic devices.
(C) A snapshot of pearls in a microfluidic device indicating the parameters used to quantify the pearls assembled.
(D) Thread thickness maps with corresponding flow velocities (Y axis: water flow; X axis: oil flow).
(E) Thread thickness chart.
(F) Pearl area map.

For this project, researchers created an in vitro 3D model to study the symbiosis between eukaryotic organisms (bone marrow mesenchymal stem cells, hBM-MSC) and prokaryotic cells (engineered non-pathogenic bacteria Lactococcus lactis, Lactococcus lactis).

Although bacteria are often used as affordable "production organisms" for protein in bioprinting, they can also serve as a mechanism for guiding cell growth and differentiation. Glasgow researchers also used sulfamethoxazole, a bacteriostatic antibiotic, to prevent harmful bacterial growth.

Four kinds of 3D printing shapes, including straight lines, triangles, squares and circles, are made. They are arranged as follows:
Line - Two Discs (180 Degree Angle)
Triangle (60 degrees interior angle)
Quadrangle (90 degrees inside)

Eight are round (135 degrees inner angle, octagon)

Microfluidic systems enable researchers to create "monodisperse" constructs suitable for drug screening, biological research and personalized medical applications.

(SEM images of alginate containing cells, phase contrast images of alginate microgel and MSC in basal medium)

(A) alginate microgel and MSC in osteogenic medium; 
(B) contains two Lactococcus lactis;
(C) alginate microgel of colony MSC, which expresses FNIII 7-10 or BMP-2 in a constitutive manner. Fixed the sample after two weeks of culture. Scale: 100 um. The SEM image of alginate was constructed by MSC in the basic medium. The image showed the label imposed by cells on the cross section of alginate construct;
(D) alginate microgel containing MSC and Lactococcus lactis had more than two colonies;
(E) alginate microgel, MSC in the osteogenic medium, round body covering cells, lumen and thin membrane like constructs;
(F) Compared with their state in aqueous media, hydrogels dehydrate slightly/shrink slightly;

The connectivity of Pearl lace hydrogels can provide a gradient method in which the relative density of each cell type can be controlled. It can also be used in time series indexing research and provides an average value for the low-cost, easy-to-manufacture 3D bioprinting prototype shown in this study.

The microgel in this study has been used as a conceptual validation for modeling of adjustable platform. Hydrogel as a ECM and growth factor can be produced at low cost and designed with high accuracy in time and space control. It has been trying to further design more aspects of the in vitro system, paving the way for cell research, and controlling the interaction with the adjustable dynamic ECM-like environment.

With the progress of bioprinting continues to dominate global research, scientists have created new bioprinting ink, 3D printing micro-surface, progressive microfluidic technology and so on.

(A) Under laminar flow conditions, the particle size (long axis) distribution of hydrogels generated by two miscible flows was studied using the flow rate of 500 MLH-1 and 5000 MLH-1 for the external phase. N / 5-10 microgel was analyzed for each condition. The average length of the pearls was 167 um and the RSD was 3.2%. Scale: 100 um.

(B) Encapsulation efficiency of cells (MSC and Lactococcus lactis) formed by hydrogel. Cell counts at each time point were measured eight times at room temperature at 30-minute intervals, lasting two hours.

(C) fluorescence images of two week old algae acid gel with Lactococcus lactis and MSC. For MSC, the BacLight Bacterial Activity Kit and Vitality/Cytotoxicity Kit of Lactococcus lactis were used to stain the hydrogel. Both kits stained living cells with green (SYTO 9 and Calein AM) and inactive cells with red (propidium iodide and Ethidium homodimer-1). The 50:50 mixture of the kits was used for co-culture. Scale: 100 um.

(D) Survival of Lactococcus lactis, MSC and co-culture.

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