Investigation of mechanical properties of soft hydrogel microcapsules in relation to protein delivery using a MEMS force sensor

Abstract

This article reports the investigation of mechanical properties of alginate-chitosan microcapsules and the relation to protein delivery. For microscale compression testing, a system based on a microelectromechanical systems (MEMS) capacitive force sensor was developed. The bulk microfabricated capacitive force sensors are capable of resolving forces up to 110 microN with a resolution of 33.2 nN along two independent axes. The monolithic force sensors were directly applied to characterizing mechanical properties of soft hydrogel microparticles without assembling additional end-effectors. Protein-loaded alginate-chitosan microcapsules of approximately 20 mum in diameter were prepared by an emulsion-internal gelation-polyelectrolyte coating method. Young's modulus values of individual microcapsules with 1, 2, and 3% chitosan coating were determined through microscale compression testing in both distilled deionized (DDI) water and pH 7.4 phosphate-buffered saline (PBS). Protein release rates were also determined in DDI water and PBS. Finally, protein release rates were correlated with mechanical properties of the microcapsules.

Quantifying growth mechanics of living, growing plant cells in situ using microrobotics

“…Despite the metrological limitations of the cantilever as a force sensor, few viable alternatives exist [13]. MEMS based force sensors have been used for multiple applications in biological research, such as for measuring forces on single heart cells [14], measuring the injection force on Drosophila embryos [15], studying cell mechanical response [16], characterizing fruit fly behavior and investigation of micromechanical properties of mouse zona pellucida and of soft hydrogel microcapsules [17][18][19]. These sensors are capable of measuring local properties of biological materials and microfabricated MEMS grippers have been demonstrated for quantifying global mechanical properties [20][21][22].…”

Effect of formulation factors on the bioactivity of glucose oxidase encapsulated chitosan–alginate microspheres: In vitro investigation and mathematical model prediction

“…However, the chitosanreinforced microspheres allow minimal GOX diffuse out, while permitting small molecules diffusion in and out readily. Owing to the presence of ionizable carboxylic groups in alginate chains, the GOX-MS showed pH-dependent swelling and softness with higher swelling in pH 7.4 buffer than in water with a pH close to 6 (Kim et al, 2010). Because the amount and rate of H 2 O 2 generated by GOX-MS are important for achieving treatment efficacy while minimizing systemic toxicity, we investigate herein how formulation factors, such as particle size, GOX loading, and glucose concentration, would influence H 2 O 2 production by experiments and model prediction, for the rational design of GOX-MS formulation.…”

“…After GOX loading into the microspheres, chitosan in a dilute solution was introduced to form 3-dimentional networks with alginate by ionic complexation. The resultant hydrogel microspheres are highly swollen and soft with Young's modulus close to blood cells (Kim et al, 2009(Kim et al, , 2010. However, the chitosanreinforced microspheres allow minimal GOX diffuse out, while permitting small molecules diffusion in and out readily.…”

Servo-Assisted Position-Feedback MEMS Force Sensor with Tunable Sensitivity and Sub-Nanonewton Range

“…A common drawback in force sensors is the inherent trade-off between the measurement range and sensitivity. Typically, MEMS force sensors do not exhibit the ability to adapt the range and sensitivity depending on the external applied force [4], which instead would be a desirable feature in many applications. The MEMS force sensor, here presented, allows tunable measurement range and sensitivity, exploiting an electrical servo-assisted mechanism with position-feedback [5] to keep the mechanical structure in a fixed position thus allowing to measure an applied external force offering a virtually infinite mechanical impedance.…”