Soft Polymer-Based Technique for Cellular Force Sensing

Abstract

Soft polymers have emerged as a vital type of material adopted in biomedical engineering to perform various biomechanical characterisations such as sensing cellular forces. Distinct advantages of these materials used in cellular force sensing include maintaining normal functions of cells, resembling in vivo mechanical characteristics, and adapting to the customised functionality demanded in individual applications. A wide range of techniques has been developed with various designs and fabrication processes for the desired soft polymeric structures, as well as measurement methodologies in sensing cellular forces. This review highlights the merits and demerits of these soft polymer-based techniques for measuring cellular contraction force with emphasis on their quantitativeness and cell-friendliness. Moreover, how the viscoelastic properties of soft polymers influence the force measurement is addressed. More importantly, the future trends and advancements of soft polymer-based techniques, such as new designs and fabrication processes for cellular force sensing, are also addressed in this review.

Keywords: 3D matrix; cell-friendly; cellular biomechanics; force-sensing; hydrogel; soft polymer; tissue engineering.

Figure 1

Schematics for TFM techniques (not to scale).

Figure 2

Schematics of EMP. (a) Methodology for cellular force sensing with EMP; (b) Tightly arranged short micro-pillars; (c) Loosely arranged micro-pillar matrix with varying heights; (d) Anisotropic pillar designs arrays.

Figure 3

Schematics showing the variation of contraction assays based on dislodge time. (a) Immediate dislodge; (b) No dislodge; (c) Dislodge after a period of time.

Figure 4

Schematic shows the methodology of the new nano-biomechanical technique for cellular force measurement.

Figure 5

Schematic diagram of a typical CFM system.

Figure 6

Schematics of typical constitutive models for viscoelastic materials. (a) Maxwell model; (b) Kelvin-Voigt model; (c) Standard linear solid (SLS) model; (d) Maxwell-Wiechet model. E and η are the elastic modulus of the elastic spring element and the viscosity of the damper element respectively.

Figure 7

Brightfield microscopy images of human dermal fibroblasts in collagen hydrogel matrix with three different seeding densities. Images showing cell morphology post 48h incubation period.