Cell‐Responsive Synthetic Hydrogels

Abstract

OLED Fabrication and Measurements: Pre-patterned indium tin oxide (ITO) substrates with an effective individual device area of 3.14 mm 2 were cleaned by sonication in a detergent solution for 3 min and then washed with large amount of doubly distilled water. Further sonication in ethanol for 3 min followed before blowing dry with a stream of nitrogen. The ITO substrates were then treated with O 2 plasma for one minute before being loaded into the vacuum chamber. The organic layers were deposited thermally at a rate of 0.1± 0.3 nm s ±1 under a pressure of~2 10 ±5 torr in an Ulvac Cryogenic deposition system. An alloy of Mg and Ag (ca. 10:1, 50 nm) was deposited as the cathode, which was capped with 100 nm of Ag. The current±voltage±luminance was measured in ambient with a Keithley 2400 Source meter and a Newport 1835C Optical meter equipped with 818ST silicon photodiode [19] The related Ir(piq) 3 complex was briefly mentioned in a recent conference paper by S. Ohada and co-workers. The device based on this complex gave a maximum bightness 10 000 cd m ±2 at J = 365 mA cm [20] The red iridium phosphors in this study have a 1-(phenyl)isoquinoline framework. In our new findings, iridium complexes bearing a 3-(phenyl)-isoquinoline framework also show an efficient yellow phosphorescence emission (565 nm) with a maximum brightness 65 000 cd m Cell-Responsive Synthetic Hydrogels** By Matthias P. Lutolf, George P. Raeber, Andreas H. Zisch, Nicola Tirelli, and Jeffrey A. Hubbell* An important part of tissue function relies on the dynamic dialog that exists between cells and their extracellular matrices (ECM): the ECM is active, presenting bound adhesion sites that interact with cell-surface receptors, [1] and it is responsive to signals presented by cells, locally degrading under the influence of proteases at the surface of the migrating cell.[2±4] While artificial biomaterial matrices used in cell culture and tissue engineering have been developed to be responsive to physical [5±9] and even biochemical [10±14] stimuli, they do not widely address this concept of responsiveness to cellular stimuli. We mimicked these features in synthetic hydrogel networks, for application in both cell biology and tissue engineering, [15±17] incorporating pendant receptor-binding sites so that cells can exert traction [18] and crosslinking protease-sensitive degradation sites so that cells can create a path to enable forward movement. [19] Our results demonstrate that synthetic materials can be responsive to cellular influences in vitro and in vivo, including here, as an example, inducing and responding to angiogenic invasion. We formed polymer networks in situ using conjugate addition reactions. We linked molecular building blocks performing either structural (poly(ethylene glycol), PEG) or biological (oligopeptides) function (Scheme 1). Vinyl sulfone (VS)-functionalized multiarmed telechelic PEG macromers reacted with thiolate groups of cysteine-containing peptides by conjugate addition, [20] a reaction that is highly selective versus b...

Versatile click alginate hydrogels crosslinked via tetrazine–norbornene chemistry

“…In tissue engineering applications where cell trafficking within the hydrogel is desirable, click alginate hydrogels could be processed using existing techniques to introduce microscale porosity to the hydrogels [50,51]. Alternatively, click alginate polymers could be crosslinked using tetrazine or norbornene-modified matrix metalloproteinase-degradable peptide sequences to allow cell-mediated degradation [29,52]. The use of partially oxidized alginate polymers would also allow degradation of the hydrogel over controlled time scales for in vivo tissue engineering applications [20,53].The tissue compatibility and stability of click alginate hydrogels could make it particularly useful for applications where isolation from host immune cell infiltration is required [54,55].…”

Moving from static to dynamic complexity in hydrogel design

“…Generally, the hydrogels are formed by reacting a multifunctional polymer (for example, PEG macromers with vinyl sulphones or acrylates) with end groups of proteasesensitive peptides (for example, thiols from cysteine moieties), where cells and molecules can be encapsulated during gelation. The remodelling of hydrogels by cells was observed for hydrogels where both sequences for adhesion and degradation were present 50 , with degradation rates controlled by crosslink density and peptide specificity 51 . This approach has been used in numerous cases to permit cell-mediated degradation of hydrogels, leading to engineered constructs for tissues such as bone and vascular structures 49,52 , including examples of the incorporation of growth factors released via cellular cues 53 .…”

Effects of neighboring sulfides and pH on ester hydrolysis in thiol–acrylate photopolymers

“…Previous work has demonstrated that network degradation can be used to control drug release temporally and influence tissue formation [1,2,6,9,11,14,20,21,[25][26][27][28][29]. Degradation in covalently crosslinked polymeric biomaterials has been achieved through hydrolytic cleavage of esters and anhydrides and also through enzymatically induced cleavage of select peptide sequences that have been incorporated into the material [2,22,27,[30][31][32].…”