206 research outputs found
Dual Photosensitive Polymers with Wavelength-Selective Photoresponse
Polyurethane thin films that photopolymerize and photodegrade upon exposure to light of different wavelengths are presented. The chromic response is based on two caged monomers with the ability to be activated or photocleaved with different wavelengths under single and two-photon excitation. This material represents a dual photoresist with "positive" and "negative" tone contained in a single resist formulation and with the ability to generate complex 2D and 3D patterns.The authors thank the DFG-ANR bilateral funding program for financial support (ANR- 09-BLAN-0426–01 and DFG CA880/3–1). Andreas Best, Dr. K. Koynov and Dr. F. Laquai (MPIP Mainz) are gratefully acknowledged for their help with the two-photon exposure
Sequential uncaging with green light can be achieved by fine-tuning the structure of a dicyanocoumarin chromophore
We report the synthesis and photochemical properties of a series of dicyanocoumarinylmethyl (DEAdcCM)- and dicyanocoumarinylethyl (DEAdcCE)-based photocages of carboxylic acids and amines with absorption maximum around 500 nm. Photolysis studies with green light have demonstrated that the structure of the coumarin chromophore as well as the nature of the leaving group and the type of bond to be photocleaved (ester or carbamate) have a strong influence on the rate and efficiency of the uncaging process. These experimental observations were also supported by DFT calculations. Such differences in deprotection kinetics have been exploited to sequentially photolyze two dicyanocoumarin-caged model compounds (e.g. benzoic acid and ethylamine), and open the way to increasing the number of functional levels that can be addressed with light in a single system, particularly when combining dicyanocoumarin caging groups with other photocleavable protecting groups that remain intact under green light irradiation
Site-Specific Installation and Study of Electroactive Units in Every Layer of Dendrons
While encapsulation of functional groups at the core of dendrimers is well-understood, very little is known about their intermediate layers or even the periphery. Here we report on a systematic investigation of every layer of dendrimers by incorporating a single ferrocene unit in well-defined locations in dendrons. Site-specific incorporation of the ferrocene unit was achieved utilizing the dendrimer sequencing methodology. We show here that the redox potential values of ferrocene at intermediate layers were remarkably different from that at the core and the periphery. While redox potential values were location-dependent, no significant change in the rate of heterogeneous electron transfer (k0) was observed with respect to locations. This was attributed to the possibility that free rotation of dendrimer nullifies the distance between the electrode and ferrocene unit. Finally, we also show that no Faradaic current was observed for the amphiphilic assemblies of these dendrons, while the same dendron did exhibit significant Faradaic current in non-assembling solvent environments
Photoregulated hydrazone-based hydrogel formation for biochemically patterning 3D cellular microenvironments
Photodriven click reactions have emerged as versatile tools for biomaterial synthesis that can recapitulate critical spatial and temporal changes of extracellular matrix (ECM) microenvironments in vitro. In this article, we report on the synthesis of poly(ethylene glycol) (PEG) hydrogels using photodriven step-growth polymerization, where one of the reactive functionalities is formed by a photocleavage reaction. Upon photocleavage, an aldehyde functionality is generated that rapidly reacts with hydrazine-functionalized PEGs; the gelation kinetics and final material modulus are distinctly controlled by variations in the light intensity. This light-driven aldehyde generation is further exploited to install biochemical ligands in the hydrazone-based hydrogels with precise spatial control. We expect that user-directed spatial and temporal control over both biophysical and biochemical gel properties through photochemical reactions and photopatterning, respectively, should provide newfound opportunities to probe and understand dynamic cell-matrix interactions
Photoregulated hydrazone-based hydrogel formation for biochemically patterning 3D cellular microenvironments
\u3cp\u3ePhotodriven click reactions have emerged as versatile tools for biomaterial synthesis that can recapitulate critical spatial and temporal changes of extracellular matrix (ECM) microenvironments in vitro. In this article, we report on the synthesis of poly(ethylene glycol) (PEG) hydrogels using photodriven step-growth polymerization, where one of the reactive functionalities is formed by a photocleavage reaction. Upon photocleavage, an aldehyde functionality is generated that rapidly reacts with hydrazine-functionalized PEGs; the gelation kinetics and final material modulus are distinctly controlled by variations in the light intensity. This light-driven aldehyde generation is further exploited to install biochemical ligands in the hydrazone-based hydrogels with precise spatial control. We expect that user-directed spatial and temporal control over both biophysical and biochemical gel properties through photochemical reactions and photopatterning, respectively, should provide newfound opportunities to probe and understand dynamic cell-matrix interactions.\u3c/p\u3
Recommended from our members
PMSE 196-Separation and identification of peptides utilizing supramolecular polymer assemblies
Recommended from our members
PMSE 196-Separation and identification of peptides utilizing supramolecular polymer assemblies
Amphiphilic nanoassemblies for the detection of peptides and proteins using fluorescence and mass spectrometry
Amphiphilic nanostructures provide unique environments for molecules that are incompatible with the solvent to be sequestered within their interior. These internal environments provide opportunities for concentrating an analyte or transducer molecule for detection, and the functional groups within the amphiphiles provide an opportunity for incorporating specificity or selectivity toward analytes. In this review, we discuss ways in which amphiphilic assemblies can be used to detect peptides and proteins with a particular emphasis on facially amphiphilic polymers and dendrimers.
Document Type: Revie
Synthetically Tractable Click Hydrogels for Three-Dimensional Cell Culture Formed Using Tetrazine–Norbornene Chemistry
The implementation of bio-orthogonal
click chemistries is a topic
of growing importance in the field of biomaterials, as it is enabling
the development of increasingly complex hydrogel materials capable
of providing dynamic, cell-instructive microenvironments. Here, we
introduce the tetrazine–norbornene inverse electron demand
Diels–Alder reaction as a new cross-linking chemistry for the
formation of cell laden hydrogels. The fast reaction rate and irreversible
nature of this click reaction allowed for hydrogel formation within
minutes when a multifunctional PEG-tetrazine macromer was reacted
with a dinorbornene peptide. In addition, the cytocompatibility of
the polymerization led to high postencapsulation viability of human
mesenchymal stem cells, and the specificity of the tetrazine–norbornene
reaction was exploited for sequential modification of the network
via thiol–ene photochemistry. These advantages, combined with
the synthetic accessibility of the tetrazine molecule compared to
other bio-orthogonal click reagents, make this cross-linking chemistry
an interesting and powerful new tool for the development of cell-instructive
hydrogels for tissue engineering applications
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