The semi-interpenetrating polymer network (semi-IPN) nanocomposite hydrogel (NC gel) was successfully synthesized by in situ polymerization of the monomer N-isopropylacrylamide in an aqueous hectorite Laponite suspension containing the polysaccharide alginate (AL). This semi-IPN NC gel reserved thermo-responsibility and high mechanical performance of the PNIPAm-Laponite NC gel. Cell cultures of fibroblasts (L929), human lung adenocarcinoma epithelial cells (A549). and human cervical cancer cells (HeLa) on the semi-IPN NC gels showed improved cell compatibility with addition of AL By lowering temperature, a rapid cell sheet detachment within 15 min was observed from the surface of the semi-IPN NC gel containing 0.2 w/v% of AL without trypsin treatment. The rough surface texture of the semi-IPN NC gel containing AL accelerated the cell sheet detachment, due to faster water penetration. The detached cell sheet was seeded and proliferated again, showing a good cell viability, which indicates that promising applications in tissue engineering and other biomedical fields exist. (C) 2011 Elsevier Ltd. All rights reserved.