## 7 Conclusions  
In this review, we give a short introduction to the development in stimuli-responsive MIPs, and it is obvious that stimuli-responsive MIPs will have important applications in separation, extraction, sensors, synthesized chemistry and biomedicine, _etc_. Up to now, various versatile approaches were developed to realize regulatory affinity in an imprinted network, but the approaches commonly displayed either advantages or disadvantages from different angles. Therefore, balancing the two aspects of the complex system is one of the most significant factors for outstanding responsive MIPs. In addition, new synthetic techniques, such as controlled radical polymerizations (CRPs), exhibit very fine control over polymer synthesis so that defined molecular weight, architecture, (co) monomer content and block distribution could be established in the imprinted network when the techniques were adopted for preparing responsive MIPs. This will lead to improved affinity as well as a well-defined responsibility, like a switch, due to homogeneous responsive blocks in the polymeric network in comparison with other radical polymerization. Furthermore, a variety of responsive blocks can be combined in one system step by step, affording truly multi-responsive MIPs for more extensive applications.  
At present, despite the potential uses of responsive MIPs in biomedicine, the real applications in clinical trials are very rare. For example, temperature-responsive MIPs have drawn the greatest attention as temperature-induced phase transitions are perhaps the best understood in both theoretical and practical terms. However, the difficulties to achieve local temperature changes _in vivo_ have limited their biomedical application. This is also the same problem for photo-responsive MIPs. However, MIPs that can respond to a specific biomolecule or ion are obviously of greater medical relevance. For example, sugar-responsive MIPs with insulin-binding affinity based on phenylboronic acid (a saccharide molecular receptor) [116; 117] will be a promising drug carrier candidate for diabetes therapy. Another problem is the biocompatibility of responsive MIPs. Although the suitable hydrophilic/hydrophobic equilibrium of the MIPs can be regulated elaborately, the toxicity of current material compositions,  
Figure 10: (**a**) Preparation of proton-imprinted NPs; (**b**) Reversible p\(K_{\text{a}}\) shift of carboxylic acids in NPs triggered by the phase transition of NPs. Reprinted with permission from Reference 89. Copyright 2014, [PERSON].  
such as \(N\)-alkylacrylamide and azobenzene monomers, should be seriously considered. Excitingly, biopolymer such as natural thermo- and pH-responsive polypeptides and biocompatible PEO and PPO block co-polymers such as pluronics, poloxamers and tetronics are available substituted candidates _in vivo_. Therefore, the development of responsive MIPs with biocompatible properties is a challenge that can be expected to yield a new generation of drug delivery devices, bioseparation devices, biosensors and tissue engineering materials for biomedical applications.  
Supplementary Information  
Supplementary materials can be accessed at: [[http://www.mdpi.com/2073-4360/7/9/1478/s1](http://www.mdpi.com/2073-4360/7/9/1478/s1)]([http://www.mdpi.com/2073-4360/7/9/1478/s1](http://www.mdpi.com/2073-4360/7/9/1478/s1)).