Quantification of cellular penetrative forces using lab-on-a-chip technology and finite element modeling

Abstract

Tip-growing cells have the unique property of invading living tissues and abiotic growth matrices. To do so, they exert significant penetrative forces. In plant and fungal cells, these forces are generated by the hydrostatic turgor pressure. Using the TipChip, a microfluidic lab-on-a-chip device developed for tip-growing cells, we tested the ability to exert penetrative forces generated in pollen tubes, the fastest-growing plant cells. The tubes were guided to grow through microscopic gaps made of elastic polydimethylsiloxane material. Based on the deformation of the gaps, the force exerted by the elongating tubes to permit passage was determined using finite element methods. The data revealed that increasing mechanical impedance was met by the pollen tubes through modulation of the cell wall compliance and, thus, a change in the force acting on the obstacle. Tubes that successfully passed a narrow gap frequently burst, raising questions about the sperm discharge mechanism in the flowering plants.

Applications of microfluidics for studying growth mechanisms of tip growing pollen tubes

“…The beam deformation was measured using optical microscopy and image analysis and was used to quantify the growth force. The amount of growth force estimated from analysis on vertical PDMS microcantilever was very similar to the value quantified from the interaction with microgaps [5]. …”

“…Individual pollen tubes elongating through the microchannels interact with microgaps made of polydimethylsiloxane (PDMS), resembling the apoplast of the transmitting tissue. The results of interaction show that pollen tubes are able to exert their penetrative force (wedge force) into the gaps and deform these micro-constricts [5]. It was also observed that some of pollen tubes burst during interaction with PDMS obstacles.…”

“…It was demonstrated that the pollen tubes are very sensitive to the fluid velocity within the microchannel and thus excess flow velocity may cease the tube elongation or cause cell bursting [3]. Due to the structure of serially arranged microchannels, different biosensors such as microgaps or microcantilevers were later integrated along the microchannels to detect the response of pollen tube to external chemical, mechanical or electrical signals [5]. Pollen tubes do not elongate in a steady fashion, but display oscillatory dynamic growth [6].…”

“…We have recently developed a microfluidic device to investigate penetrative force of pollen tube [5]. In this device, the TipChip design was adapted by incorporating mechanical constricts along the growth microchannels.…”

Massively Parallelized Pollen Tube Guidance and Mechanical Measurements on a Lab-on-a-Chip Platform

“…thaliana pollen tubes. The TipChip and its variants have been used to study the influence of obstacles and chemical targeting on the growth of Camellia japonica pollen tubes as shown by Geitmann and colleagues [13,14]. Higashiyama and coworkers have used Torenia fournieri to study pollen tube guidance and pollen tube-female tissue interaction and A .…”