Polymeric nanoparticles for cancer therapy

Purpose: Conventional cancer chemotherapy suffers from poor tumour selectivity, high required doses, systemic toxicity, rapid drug elimination, and multidrug resistance. Polymeric nanoparticles (NPs) are reviewed as a strategy to improve targeted delivery, controlled release, and therapeutic efficacy while reducing adverse effects.

Hypothesis: This is a review article and does not test a single formal hypothesis. Its central premise is that polymeric NPs — especially biodegradable, biocompatible nanospheres, nanocapsules, and solid lipid NPs — can improve cancer therapy by passive and active targeting, controlled drug release, improved pharmacokinetics, and enhanced accumulation in tumour tissue.

Aims: Provide an overview of clinically applicable NPs for cancer therapy. - Review different types of nanoscale polymer carriers used to deliver chemotherapeutic agents. - Describe mechanisms that facilitate targeted delivery to tumour cells. - Compare passive targeting (EPR effect, localised delivery) with active targeting (ligand–receptor, antigen–antibody, aptamer). - Highlight examples of polymeric NPs delivering anticancer drugs such as paclitaxel, doxorubicin, methotrexate, and quinine.

Delivery system: Particle types: Polymeric nanospheres, nanocapsules, and solid lipid nanoparticles (SLNs); size range generally 10–1000 nm. - Polymers: PLGA, PLA, PCL, poly(cyanoacrylate), PEG, diblock copolymers such as poly(γ-benzyl-L-glutamate)/PEG, PLGA–PEG, dendrimers, and other biodegradable polyesters. - Payloads: Paclitaxel (TX), doxorubicin (DOX), methotrexate, quinine dihydrochloride, and other chemotherapeutic agents. - Targeting ligands: Lectins/carbohydrates (wheat germ agglutinin, galactose), transferrin (Tf), folate, antibodies, aptamers, RGD peptide, and others. - Targeting mechanisms: Passive EPR effect, localised/intratumoral delivery, ligand–receptor interaction, antigen–antibody interaction, and aptamer-mediated targeting. - Key design features: Biocompatibility, biodegradability, sustained/controlled release, surface modification, PEGylation, and conjugation with targeting ligands.

Approach: Review of in vitro and in vivo literature. In vitro cell lines include A549, H1299, HepG2, MCF-7, MCF-7/Adr, C6, 4T1, KB, and others. In vivo models include S-180 solid tumour-bearing mice, subcutaneous prostate cancer mice, 4T1 mouse breast cancer, nude mice xenografts, and immunodeficient mice bearing human KB tumours. No new primary experiments, group sizes, or doses are reported.

Key methods: Nanoparticle characterisation: size, size distribution, morphology, and biocompatibility. - Cellular uptake and intracellular retention: flow cytometry, confocal microscopy. - Cytotoxicity: IC50 determination. - In vivo biodistribution, tumour accumulation, and retention. - Tumour volume, survival rate, and lifespan measurements. - Plasma drug levels and tissue distribution. - Targeting validation: receptor-mediated endocytosis, ligand competition, and aggregation assays.

Key results: Transferrin-conjugated paclitaxel NPs: Direct intratumoral injection in a subcutaneous prostate cancer mouse model produced complete tumour regression at a single TX dose of 4 mg/kg, with greater survival than TX-NPs or TX-Cremophor EL. - Transferrin-PEG polycyanoacrylate NPs: Tumour TX concentrations were 4.8-fold and 2.1-fold higher than free TX injection and PEG-NPs without transferrin, respectively, at 6 h after intravenous injection; tumour volume was smaller and lifespan increased. - Folate-decorated PLGA–vitamin E TPGS NPs: Cellular uptake was 1.5-fold higher in MCF-7 and 1.7-fold higher in C6 cells versus non-folate NPs after 30 min; lower IC50 than free DOX after 24 h. - Folate-conjugated DOX micelles: IC50 was 3.8 vs. 7.6 mg/L for 4T1 cells and 1.2 vs. 3.0 mg/L for KB cells compared with non-folate micelles; in vivo tumour volume significantly regressed. - WGA-conjugated PLGA NPs: Superior in vitro cytotoxicity against A549 and H1299 cells compared with TX-loaded NPs without WGA or IPM. - Galactose-modified PEG-b-PLG NPs: HepG2 cells overexpressing asialoglycoprotein receptors were more sensitive to TX-loaded NPs than free TX. - Folate-conjugated dendrimers: Concentrated in tumour and liver tissue over 4 days after administration; internalisation into tumour cells confirmed by confocal microscopy. - Transferrin-conjugated SLNs: Enhanced brain uptake of quinine compared with unconjugated SLNs or free drug.

Interpretation: Polymeric NPs have the potential to address major limitations of cancer chemotherapy by improving drug solubility, stability, circulation time, tumour accumulation, and intracellular delivery. Passive targeting via the EPR effect and active targeting via ligands can increase drug concentration in tumours and reduce systemic toxicity. Polymeric NPs may also help overcome multidrug resistance and blood–brain barrier limitations. The authors present these systems as promising, clinically applicable candidates for cancer drug delivery.

Limitations: This is a review, not a primary study; no new experimental data or meta-analysis. - The provided PDF excerpt ends before the conclusion, so final summary remarks are not available. - Most discussed systems are preclinical; clinical translation, long-term safety, and large-scale manufacturing are not comprehensively addressed. - Passive EPR-based targeting is heterogeneous and may not work equally in all tumours. - Active targeting adds complexity and may face issues such as receptor expression variability, immunogenicity of ligands, and manufacturing challenges. - No large-animal validation or detailed clinical trial results are presented.