Transformation of hard pollen into soft matter

Abstract

Pollen's practically-indestructible shell structure has long inspired the biomimetic design of organic materials. However, there is limited understanding of how the mechanical, chemical, and adhesion properties of pollen are biologically controlled and whether strategies can be devised to manipulate pollen beyond natural performance limits. Here, we report a facile approach to transform pollen grains into soft microgel by remodeling pollen shells. Marked alterations to the pollen substructures led to environmental stimuli responsiveness, which reveal how the interplay of substructure-specific material properties dictates microgel swelling behavior. Our investigation of pollen grains from across the plant kingdom further showed that microgel formation occurs with tested pollen species from eudicot plants. Collectively, our experimental and computational results offer fundamental insights into how tuning pollen structure can cause dramatic alterations to material properties, and inspire future investigation into understanding how the material science of pollen might influence plant reproductive success.

The influence of arm composition on the self-assembly of low-functionality telechelic star polymers in dilute solutions

“…Self-organization of building blocks due to external stimuli is ubiquitous in most materials and all living organisms in nature. Inspired by this, a remarkable body of work has been performed to understand and emulate their response to temperature [1][2][3], pH [4][5][6] and light [7,8], enabling the controlled design of their structure assembly. Recent advances in polymer chemistry have led to the synthesis of various building blocks with complex architectures and functionalized properties.…”

Actuation and locomotion driven by moisture in paper made with natural pollen

“…Importantly, pollenderived microcapsules have been developed as nonallergenic carriers to harness such advantageous properties as high mechanical strength, chemical stability, UV protection, and pathogen inhibition (51,52). Recently, we also demonstrated that it is possible to convert hard pollen grains into soft, stimuliresponsive microgel particles (53). However, the potential for developing other material forms based on natural, nonallergenic, and inexpensive pollen grains, thereby harnessing their unique functional capabilities and applications, has not been investigated to date.…”

Influence of Chemical and Physical Change of Pollen Microgels on Swelling/De‐Swelling Behavior

“…This is because the stiff pollen shell restricts the swelling of the pollen microgel. [ 31 ] These results indicate that two processes control the volume change of the pollen microgel. 1) The deprotonation of the carboxyl group in pectin acts a key role to provide the internal force for swelling/de‐swelling.…”

“…Recently, we developed the soapmaking‐like process to transform the pollen particles into the pollen microgels, which show great potential as a functional carrier for drug/protein delivery. [ 31 ] The pollen microgel particles also show pH‐ and ion‐ responsive swelling/de‐swelling behavior. The de‐esterification of pectin in the intine layer plays an important role in pollen gelation behavior.…”

“…[ 32,33 ] We previously reported that 6 species of pollen were successfully transformed into pH‐responsive microgels without destroying the morphology of the pollen wall. [ 31 ] However, the influence of parameters involved in the synthesis on the physical and chemical properties of the pollen microgel are still unknown.…”