Schematic illustration of nanocarrier-based drug delivery systems (NDDS) for improving cancer chemotherapy based on different strategies. (A) Targeted drug delivery 45. Copyright 2016, ACS Publications, (B) Promoting tissue penetration 59. Copyright 2016, ACS Publications, (C) Mitochondria-targeted chemotherapy 74. Copyright 2018, Elsevier, (D) Nucleus-targeted chemotherapy 78. Copyright 2015, Wiley-VCH, (E) Golgi-targeted chemotherapy 80. Copyright 2019, ACS Publications, (F) Inhibition of P-gp 97. Copyright 2017, Wiley-VCH, (G) π-π stacked dual anticancer drug 98. Copyright 2016, Wiley-VCH, (H) Combination with PDT 136. Copyright 2020, Wiley-VCH, (I) Combination with PTT 142. Copyright 2020, Wiley-VCH, (J) Combination with CDT 113. Copyright 2020, ACS Publications, (K) Combination with radiotherapy 114. Copyright 2017, Wiley-VCH, (L) Combination with gas therapy 163. Copyright 2018, ACS Publications, (M) Combination with immunotherapy 166. Copyright 2021, Elsevier, (N) Multiple combination therapy 133. Copyright 2019, Wiley-VCH.