Microcapillary cell extrusion deposition with picolitre dispensing resolution

Extrusion-based cell deposition has become a prominent technique for expanding bioprinting applications.However,the associated print resolution in the order of nanolitre or above has been a limiting factor.The demand for improving print resolution towards the scale of a single cell has driven the development of precision nozzle extrusion,although the benefits gained remain ambiguous.Here,aided by in situ imaging,we investigated the dynamics of cell organisation through an extrusion-based microcapillary tip with picolitre precision through in-air or immersion deposition.The microcapillary extrusion setup,termed‘Picodis’,was demonstrated by generating droplets of colouring inks immersed in an immiscible medium.Next,using 3T3 fibroblast cells as an experimental model,we demonstrated the deposition of cell suspension,and pre-aggregated cell pellets.Then,the dynamic organisation of cells within the microcapillary tip was described,along with cell ejection and deposition upon exiting the tip opening.The vision-assisted approach revealed that when dispersed in a culture medium,the movements of cells were distinctive based on the flow profiles and were purely driven by laminar fluid flow within a narrow tip.The primary process limitations were cell sedimentation,aggregation and compaction,along with trapped air bubbles.The use of picolitre-level resolution microcapillary extrusion,although it provides some level of control for a small number of cells,does not necessarily offer a reliable method when a specified number of cells are required.Our study provides insights into the process limitations of high-resolution cell ink extrusion,which may be useful for optimising biofabrication processes of cell-laden constructs for biomedical research.

Isolation and diagnosis of Helicobacter pylori by a new method: Microcapillary culture

AIM:To investigate the performance of the microcapillary culture method(MCM) in Helicobacter pylori(H.pylori) isolation and diagnosis.METHODS:Microcapillary culture(MC),classical culture(CC),rapid urease(CLO) test,and histopathologic examination(HE) were performed with biopsy samples.Homogenized biopsy samples were loaded into capillary tubes and incubated for 48 h at 37 ℃ without providing a microaerophilic environment.Additionally,three or four loops of the homogenized sample were inoculated in a ready-to-use selective medium(Becton Dickinson,Helicobacter Agar,Modified) specific for the isolation of H.pylori and incubated at 37 ℃ in a microaerophilic atmosphere provided by Campy Gen(Becton Dickinson,Gas Pack).Bacteria reproducing in microcapillary tubes were evaluated in an inverted microscope and also were evaluated after performing a CC with the content.Results obtained by CC,CLO test,and HE were compared with those of MC.The diagnostic performances of the methods used in this study were evaluated for specificity,sensitivity,positive predictive value(PPV),negative predictive value(NPV),and CI.RESULTS:H.pylori was found positive by CLO test +HE and/or CC culture in 26 patient antrum and corpus biopsy samples.In 25(25/26) patient biopsy samples,H.pylori was isolated by MCM,whereas in only 14(14/26) patient biopsy samples,H.pylori was isolatedby CC.CLO test and HE were found positive in 17(17/26) patient biopsy samples.Comparing the results of the isolation of H.pylori by MCM,CC,CLO test,and HE,the sensitivity of the MCM was found as 96%,the specificity as 80%,the PPV as 83%,the NPV as 95%,and the 95%CI as 0.76(χ2 =31.51,P < 0.01) whereas the sensitivity of the CC was found as 54%(χ2 =19.15,P < 0.01),and the sensitivity of the CLO test and HE were found as 65%(χ2 =25.26,P < 0.01).CONCLUSION:This new microcapillary cultivation method for H.pylori has high diagnostic sensitivity compared with CC,HE,and CLO tests.

Debye-Hckel solution for steady electro-osmotic flow of micropolar fluid in cylindrical microcapillary

Analytic expressions for speed, flux, microrotation, stress, and couple stress in a micropolar fluid exhibiting a steady, symmetric, and one-dimensional electro-osmotic flow in a uniform cylindrical microcapillary were derived under the constraint of the Debye-Hiickel approximation, which is applicable when the cross-sectional radius of the microcapillary exceeds the Debye length, provided that the zeta potential is sufficiently small in magnitude. Since the aciculate particles in a micropolar fluid can rotate without translation, micropolarity affects the fluid speed, fluid flux, and one of the two non-zero components of the stress tensor. The axial speed in a micropolar fluid intensifies when the radius increases. The stress tensor is confined to the region near the wall of the mi- crocapillary, while the couple stress tensor is uniform across the cross-section.