The AIEgen TPA-NDTA (TN) was synthesized in accordance with our previously reported protocol, and its synthetic route was displayed in Figure . The monodispersed PNA nanogels were prepared by precipitation polymerization, and its structure was shown in Figure . According to UV-vis spectrum (Figure ), the compound TN in tetrahydrofuran (THF) solution exhibited a characteristic absorption wavelength at 748 nm. After encapsulating TN into nanogels, the P-TN nanogels showed a strong and broad absorption in NIR range with an absorption peak of 808 nm, showing an evident red-shift of 60 nm by virtue of the improved molecular planarity within nanogels. The characteristic absorption peak of Dox was observed in P-TN-Dox, revealing the successful loading of Dox into the nanogels. It is noteworthy that the absorption spectrum of P-TN-Dox@CM nanogels was barely altered compared with the P-TN-Dox nanogels. The fluorescence emission spectrums were studied under the excitation of 850 nm laser. As shown in Figure , free TN in THF can emit bright fluorescence with a maximum emission wavelength of 1090 nm. After incorporating TN and Dox into the nanogels, the maximum emission wavelength displayed a slight red-shift of ~16 nm, which was attributed to the augmented intermolecular interactions in aggregate state. The maximum emission wavelength exhibited a trifling blue-shift of ~6 nm after the tumor cell membrane cloaking, possibly due to the changed molecular conformation. Encouraged by the strong and broad emission spectrum of nanogels coupling with the substantial potential of fluorescence imaging in clinic, we then evaluated the fluorescence signal intensity of various nanogels with different concentrations. As shown in Figure , PNA nanogels displayed no fluorescence signal, while P-TN nanogels exhibited bright fluorescence after encapsulation of TN. Additionally, the Dox-loading (P-TN-Dox) and tumor cell membrane cloaking (P-TN-Dox@CM) did not affect the fluorescence brightness of nanogels. In particular, the fluorescence signal intensity of TN-loaded nanogels showed concentration-dependent effect, which augmented in pace with the increase of nanogel concentration, revealing a typical feature of aggregation-induced fluorescence enhancement. The photostability of P-TN-Dox@CM nanogels was further evaluated in comparison with the U.S. Food and Drug Administration (FDA) approved NIR photothermic agent indocyanine green (ICG). As depicted in Figure , upon continuous 808 nm laser irradiation, the fluorescence signal intensity of ICG declined dramatically along with the laser irradiation time, and decayed entirely in 7 min, which was resulted from severe degradation. However, the fluorescence intensity of P-TN-Dox@CM nanogels exhibited no apparent change after 15 min laser irradiation, suggesting its excellent resistance to photobleaching for stable biomedical imaging. In addition, the absorption spectrum of P-TN-Dox@CM nanogels and ICG solution with different laser irradiation time also confirmed the results (Figure ). The average hydrodynamic diameters of PNA nanogels in pH 7.4 and pH 5.0 were 184 and 157 nm, and increased to 259 and 226 nm after encapsulation of TN and Dox as well as cell membrane enveloping (P-TN-Dox@CM). The hydrodynamic diameters of all nanogels demonstrated a relatively narrow distribution (Figure ). Transmission electron microscopy (TEM) images of P-TN-Dox@CM nanogels shown in inserted pictures of Figure depicted a regular spherical shape with an average diameter of ~100 nm in dry state, and provided apparent visual proof that a characteristic core-shell morphology was formed through the successful tumor cell membrane cloaking with a uniform thickness of ~10 nm. The zeta potentials of all nanogels in pH 7.4 were higher negative than that in pH 5.0 due to the lower protonated acrylic acid content. In addition, the tumor cell membrane shielding led to the highest negative zeta potential of P-TN-Dox@CM nanogels in pH 7.4 (~ -16 mV), which was beneficial to impairing the interaction with negative charged proteins and decreasing phagocytic uptake in the blood, thereby contributing to the prolongation of blood circulation time. Moreover, the Dox loading capacity increased with the increment of feeding drug concentrations (Figure ). The loading capacity and drug encapsulation efficiency of Dox reached up to 27.5% and 94.7%, respectively, when the initial concentration of Dox was 2 mg mL -1 (Figure and).