# Microsphere Polymers in Molecular Imprinting: Current and Future Perspectives
## 2 Microsphere Polymers  
Microspheres are microscopic-sized spherical particles in the range of 1-1000 \(\upmu\)m in diameter, although particles over 1000 \(\upmu\)m in size have also been described as microspheres. Microspheres have a variety of functions, especially in the biological, clinical and chemical fields. Polymer microspheres have been developed for controlled drug delivery [42; 43] and used in solid-phase extraction. This type of polymer can also be used as a diagnostic method for diseases associated with the blood [43]. Microspheres must possess specific characteristics of size, surface area, diffusion ability, stability, biocompatibility and safety. The polymer microsphere is limited to a minimum size of 5 nm and a molecular weight of 10,000 Da. The surface area of 1 g of microspheres with a diameter of 0.1 \(\upmu\)m is 60 m\({}^{2}\). The surface area will affect the chemical reactions that occur on the microsphere surface [43; 44]. Molecularly imprinted microspheres (MIMs) are used in a number of applications, such as competitive ligand bond tests, solid-phase molecular extraction (SPME), microsphere sensors and capillary electrochromatography [40]. Other applications have used MIMs for sustained drug release [45; 46; 47]. Microsphere polymers prepared using the molecular imprinting method show a more uniform pore size and higher specificity for the template molecule compared to other methods. However, the absorption capacity of the microsphere polymer is higher than that of MIMs [48]. Table 1 shows other applications of MIMs with different templates, monomers, crosslinkers and polymerisation techniques. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Application** & **Template** & **Monomer and Crosslinker** & **Polymerisation Technique** & **References** \\ \hline \multirow{5}{*}{17\(\beta\)-estradiol} & \multicolumn{1}{c}{MAA, ECDMA, TRIM} & PP & [40,41] \\ \cline{2-5}  & \multicolumn{1}{c}{4-VP, AM, TRIM} & ATRPP & [49] \\ \cline{2-5}  & \multicolumn{1}{c}{MAA, ECDMA} & PE & [50] \\ \cline{2-5}  & \multicolumn{1}{c}{MAA, ECDMA, TRIM} & PP & [40,41] \\ \cline{2-5}  & \multicolumn{1}{c}{MAA, DVB} & \multicolumn{1}{c}{[6]} \\ \cline{2-5}  & \multicolumn{1}{c}{Caffeine} & \multicolumn{1}{c}{MAA, ECDMA, TRIM} & PP & [40] \\ \cline{2-5}  & \multicolumn{1}{c}{Naproven, Diclofenac, Toltrazuril} & 4-VP, MAA, HEMA, MAAm, ECDMA, TRIM, DVB & PP & [51] \\ \cline{2-5}  & \multicolumn{1}{c}{Estradiol (E2)} & 4-VP, ECDMA & PP & [52] \\ \cline{2-5}  & \multicolumn{1}{c}{Kaempfer} & 4-VP, ECDMA & PP & [5] \\ \cline{2-5}  & \multicolumn{1}{c}{Terbutylazine} & MAA, ECDMA & PP & [53,54] \\ \cline{2-5}  & \multicolumn{1}{c}{Enofloxacine} & MAA, HEMA, DVB, ECDMA, TRIM & PP & [55] \\ \cline{2-5}  & \multicolumn{1}{c}{Nicotine} & MAA, TFMAA, DVB & PP & [56] \\ \cline{2-5}  & \multicolumn{1}{c}{MAA, EDGMA} & RAFTPP & [57] \\ \cline{2-5}  & \multicolumn{1}{c}{_Trans_-aconitic acid} & MAA, TRIM & PP & [58] \\ \cline{2-5}  & \multicolumn{1}{c}{\(\iota\)-2-chloromandelic acid} & AM, BDDA & PP & [59] \\ \cline{2-5}  & \multicolumn{1}{c}{Cinchonidine} & MAA, HEMA, DVB & PP & [60] \\ \cline{2-5}  & \multicolumn{1}{c}{Morphine} & MAA, TRIM & PP & [61] \\ \cline{2-5}  & \multicolumn{1}{c}{Cinamic Acid} & AA, DVB & PP & [62] \\ \cline{2-5}  & \multicolumn{1}{c}{Piperine} & AA, ECDMA & PP & [63] \\ \cline{2-5}  & \multicolumn{1}{c}{Mannose-tryptophan} & MMA, DVB & PP & [64] \\ \cline{2-5}  & \multicolumn{1}{c}{2-4-diamino-6-methyl-1,3-5-triazine,} & \multicolumn{1}{c}{gammazine,} & \multicolumn{1}{c}{} & \\ \cline{2-5}  & \multicolumn{1}{c}{cyromazine, trimethoprim} & MAA, DVB & PP & [65] \\ \cline{2-5}  & \multicolumn{1}{c}{Sulfamenthazine} & \multicolumn{1}{c}{4-VP, HEMA, ECDMA} & ATRPP & [66] \\ \cline{2-5}  & \multicolumn{1}{c}{Glutathione} & \multicolumn{1}{c}{4-VP, ECDMA} & \multicolumn{1}{c}{LRPP} & [67] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Applications of molecularly imprinted microspheres (MIMs).