Molecular imprinting, an established technique for the synthesis of insolub
le crosslinked polymers with specific cavities for selective molecular reco
gnition and catalysis, has been applied to highly crosslinked polymer nanop
articles (microgels) able to build stable solutions in appropriate solvents
. Imprinted microgels with a nominal crosslinking degree above 50 wt.-% cou
ld be prepared by solution polymerization in high dilution. They were chara
cterized by GPC, viscometry and membrane osmometry, and were found to be hi
ghly crosslinked macromolecules with a molecular weight comparable to the o
ne of proteins. Molecular recognition experiments clearly pointed out the p
resence of functionalized cavities within the microgels that were able to r
ecognize and to selectively bind sugar molecules. The experiment can be car
ried out in homogeneous solution, after which the microgels are convenientl
y separated by ultracentrifugation. Although the obtained selectivities are
still low compared to the results achieved with insoluble crosslinked poly
mers, the success of this approach represents an important step towards the
development of what might be properly described as "artificial enzymes".