Stimuli-responsive systems

PEGylation can also decrease the overall transfection effidency, and for this reason, stimuli-responsive systems are being developed to cleave off the PEG groups after cellular uptake. ... 

Hashidzume A, Tomatsu I, Harada A (2006) Interaction of cyclodextrins with side chains of water soluble polymers a simple model for biological molecular recognition and its utilization for stimuli-responsive systems. Pol5mier 47 6011-6027. doi 10.1016/j.poljtmer.2006.06. 021... 

X 10 cm This study provided initial proof of concept for the use of liquid crystalline matrices as on-demand stimuli-responsive systems for hydrophilic drugs. 

The applications of hydrogels in the production of medical items, resulting materials must have several features, which recommends them non-toxicity, functionability, sterilizability, biocompatibUity [115]. These characteristics are requires for wound dressings, drug delivery systems, transdermal systems, injectable polymers, implants, dental and ophthalmic applications, stimuli-responsive systems, hydrogel hybrid-type organs. 

Similar architectures have also been developed by Schubert and coauthors. Their stimuli-responsive systems relied on metal-ligand interactions between a divalent metal such as Fe " " or Zn + with the 2,2 6, 2"-terpyridine (tpy) moiety, attached as an end-group to a poly(A-isopropyl-acrylamide) backbone (13, Figure 22). 

In summary, very important progress has been made with regard to redox-responsive polymeric nanocarriers during the past decade and it seems that they will soon be among the most promising stimuli-responsive systems (which are currently the pH- and enzyme-responsive systems) when directed to peptide, protein or gene delivery. 

Stimuli-responsive systems have been designed for different architectures and specific structural properties, and have enhanced the development of new biosensors and actuators, microfluidic devices, diagnostic systems and new therapeutic treatments for diseases. Intelligent surfaces, NPs, gels and shape memory polymers (SMPs) are considered below (see Fig. 12.2). 

Stimuli-Responsive Systems Overall Release Profiles... 

There are myriad mechanisms to direct the release of drugs in a controlled manner. We can classify the drug dehvery mechanisms of special interest in tissue engineering into three main categories diffusion from nondegradable systems, bioerodible systems, and stimuli-responsive systems. Several other strategies have been employed to create desirable release profiles however, an exhaustive description is certainly beyond the scope of this chapter, and may be found in excellent reviews in the literature (Caldorera-Moore and Peppas 2009, hanger and Peppas 2003, Lavan et al. 2003, Saltzman and Olbricht 2002). 

Sensitivity, reversibility, accuracy, and self-assembly of such polymers are the keys to constructing intelligent stimuli-responsive systems and would be affected by the polymer primary structures. However, systematic investigations of the relationships between polymer structures and stimuli-responsive behavior were limited until several years ago, as the living polymerizations of related monomers involved in these syntheses were difficult to carry out. For example, the structure and molecular weight of polymers could not be freely controlled either for the conventionally investigated thermoresponsive polymers such as cellulose derivatives [8], poly(ethylene oxide) (PEO) derivatives [9], poly(methyl vinyl ether) [10], partly hydrolyzed poly(vinyl acetate) [11], and poly(M-alkylacrylamide)s [12,13], or for poly(J -isopropylacrylamide) (PNI-PAM), on which there have been advanced studies [14-18]. 

Clegg JK, Cremers J, Hogben AJ, Breiner B, Smulders MMJ, Thoburn JD, Nitschke JR (2013) A stimuli responsive system of self-assembled anionbinding Ee4L6 cages. Chem Sci 4(l) 68-76... 

ELPs were explored as potential proteol5dic stimuli-responsive systems to control the release of model protein (Xia et al., 2011). The advantage of the proposed system is that The ELPs-based matrices can be conveniently modified by insertion of sequences mimicking those of other natural proteins. In this way, functional domains can be easily incorporated to increase the biological properties of the hydrogels improving the features of the final product. 

The stimuli-responsive systems are now being widely used as drug delivery systems. 

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