TipChip

How do pollen tubes find the ovule? How do they manage to overcome the mechanical impedance of the pistillar tissue? Addressing these questions has become easier, and experiments have become more reproducible with the development of the TipChip. This Lab-on-a-Chip experimental platform is based on MEMS (microelectromechanical systems) technology and was developed in collaboration with Dr. Muthu Packirisamy, Concordia University.

Lab-on-a-Chip

Our Lab-on-a-Chip device consists of a microfluidic network that allows positioning the pollen grains in front of serially arranged microchannels. The pollen tubes grow into these channels where they are exposed to various experimental assays.

The microfluidic network is fabricated from PDMS material, and is sealed by a cover glass ensuring optimal optical qualities for brightfield and fluorescence imaging (Agudelo et al. 2012, 2013, Sanati Nezhad et al. 2012).

Agudelo CG, Packirisamy M, Geitmann A. 2016. Influence of electric fields and conductivity on pollen tube growth assessed via Electrical Lab-on-Chip. Scientific Reports 6:19812
PDF is available from the publisher or upon request

Elongating pollen tubes respond to the presence of electric fields. We designed a highly reproducible experimental setup based on Lab-on-Chip technology that allows researchers to assess the effect of electric field strengths and AC frequencies on single cells. Medium conductivity was found to be an important parameter determining the response of cells to the electric field.

Sanati Nezhad A, Geitmann A. 2015. Tip growth in walled cells: Cellular expansion and invasion mechanisms. In: Cuerrier C, Pelling A (eds) Cells, Forces and the Microenvironment, CRC Press pp. 335-355
PDF will be available from the publisher or upon request

Plant cell morphogenesis is a process governed by a set of mechanical principles which determine how and into what shape the cell grows or how it deals with mechanical obstacles. In this review the individual concepts and vocabulary of plant cell growth in general and invasive growth in particular are explained.

Sanati Nezhad A, Packirisamy M, Geitmann A. 2014. Dynamic, high precision targeting of growth modulating agents is able to trigger pollen tube growth reorientation. Plant Journal 80: 185-195
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The growing pollen tube apex represents a rapidly moving target making the local administration of drugs or proteins a challenge. We designed a microfluidic device with which we are able to target the growing region of the tube in tunable manner thus enabling its asymmetric exposure to chemical gradients with micrometer precision.
 

Ghanbari M, Sanati Nezhad A, Agudelo CG, Packirisamy M, Geitmann A. 2014. Microfluidic positioning of pollen grains in lab-on-a-chip for single cell analysis. Journal of Bioscience and Bioengineering 117: 504–511
PDF is available from the publisher or upon request

Playing pool billiard at micron-scale ..... this is what we try to achieve in the present paper. Our billiard balls are pollen grains and the pockets are the entrances of the microchannels in a microfluidic network. We haven't clarified how to identify the 8-ball yet, however.....
 

Sanati Nezhad A, Ghanbari M, Agudelo CG, Naghavi M, Packirisamy M, Bhat R, Geitmann A. 2014. Optimization of flow assisted entrapment of pollen grains in a microfluidic platform for tip growth analysis. Biomedical Microdevices 16: 23-33
PDF is available from the publisher or upon request

A key challenge in microfluidic design for single cell analysis is the positioning of the cells within the device. This is crucial in the TipChip in which pollen grains need to be placed in front of microchannels to enable the analysis of individual pollen tubes. Here we optimized fluid flow driven distribution of pollen grains over a series of traps that ensure identical experimental conditions for all cells.
 

Sanati Nezhad A, Naghavi M, Packirisamy M, Bhat R, Geitmann A. 2013. Quantification of cellular penetrative forces using Lab-on-a-Chip technology and finite element modeling. PNAS 110: 8093–8098
PDF is available from the publisher or upon request

To reach an ovule, the pollen tube needs to invade the pistillar tissues of the receptive flower. This requires the exertion of invasive and dilating forces. To quantify these forces, we used the TipChip, a microfluidic platform, and exposed in vitro growing pollen tubes with mechanical obstacles. We found that pollen tubes often burst and release the sperm cells after having passed a narrow opening. Find more information about the project .
For media coverage check University of Montreal (English, French), Live Science, Phys.org, NBC News, Science Daily, Guokr.com, ChemFeeds.
 

Sanati Nezhad A, Packirisamy M, Bhat R, Geitmann A. 2013. In vitro study of oscillatory growth dynamics of Camellia pollen tubes in microfluidic environment. IEEE Transactions on Biomedical Engineering 60: 3185-3193
PDF is available from the publisher or upon request

Pollen tubes grow in oscillatory manner. We used the TipChip, a microfluidic experimental platform, to analyze these oscillations in detail and found that the growth dynamics is characterized by primary and secondary oscillation frequencies.
 

Sanati Nezhad A, Naghavi M, Packirisamy M, Bhat R, Geitmann A. 2013. Quantification of the Young's modulus of the primary plant cell wall using Bending-Lab-On-Chip (BLOC). Lab on a Chip 13: 2599–2608
PDF is available from the publisher or upon request

The classical bending test used for the quantification of mechanical properties of rod shaped objects has been brought down to the microscopic scale with a test assay based on microfluidics technology. The device was used to quantify the Young's modulus of the pollen tube cell wall.
 

Agudelo CG, Sanati Nezhad A, Ghanbari M, Naghavi M, Packirisamy M, Geitmann A. 2013. TipChip – a modular, MEMS (microelectromechanical systems)-based platform for experimentation and phenotyping of tip growing cells. Plant Journal 73:1057-1068
PDF is available from the publisher or upon request

The TipChip is an experimental platform that allows exposing pollen tubes to a variety of experimental assays such as chemical gradients, mechanical obstacles, fluid-air interface, and electrical fields.
 

Agudelo CG, Packirisamy M, Geitmann A. 2013 Lab-on-a-Chip for studying growing pollen tubes. In: Plant Cell Morphogenesis: Methods and Protocols, Series "Methods in Molecular Biology", eds. Žárský V, Cvrčková F, Springer. pp 237-248
PDF will be available from the publisher or upon request

The fabrication of the TipChip is explained in detail and numerous hints and tips are given for successful production and use of a microfluidic platform.
 

Sanati Nezhad A, Ghanbari M, Agudelo CG, Packirisamy M, Bhat RB, Geitmann A. 2012. PDMS microcantilever-based flow sensor integration for lab-on-a-chip. IEEE Sensors Journal 13: 601-609
PDF is available from the publisher or upon request

To measure the speed of fluid flow within a microfluidic device a low cost and low-tec test assay was developed that relies on the flow-induced deformation of a calibrated PDMS cantilever. This test device allows for calibrated administration of fluid flow and shear stress.
 

Agudelo CG, Sanati Nezhad A, Ghanbari M, Packirisamy M, Geitmann A. 2012. A microfluidic platform for the investigation of elongation growth in pollen tubes. Journal of Micromechanics and Microengineering 22, 115009
PDF is available from the publisher or upon request

Studying pollen tubes one at a time is now possible using a microfluidic device that guides the elongating tubes through narrow microchannels where they can be exposed to experimental test assays.
 

 

For a complete list of publications and reprints in pdf format please click here.