Nanoparticle-based targeted drug delivery

Purpose: Nanotechnology enables control and manufacture of structures in the nanometer range, and nanoparticles exhibit novel properties that differ from bulk materials. There is a need for targeted drug delivery systems that improve solubility, bioavailability, sustained release, protection from degradation, and site-specific delivery while reducing systemic toxicity—especially for cancer, vaccines, and oral protein therapeutics.

Hypothesis: No formal experimental hypothesis. Central thesis: nanoparticle-based delivery systems—due to their small size, customizable surface, improved solubility, multifunctionality, and biodegradable materials—can enable targeted, sustained, and effective delivery of drugs, proteins, nucleic acids, and vaccines for cancer and other diseases, including overcoming drug resistance and biological barriers such as the blood–brain barrier.

Aims: Provide an overview of nanotechnology for biologists. - Describe nanoparticle delivery systems and their advantages. - Discuss characteristics important for drug delivery: particle size, surface properties, drug loading, and drug release. - Review passive and active targeted drug delivery. - Summarize nanotechnology-based drug delivery in cancer, including hydrogels, micelles, liposomes, dendrimers, nanotubes, polymersomes, quantum dots, and the authors’ XPclad nanoparticle formulation.

Delivery system: Nanoparticle types: nanocapsules, nanospheres, polymeric nanoparticles (PLA, PLG, PLGA, PCA), hydrogels (cholesterol pullulan, nanocurcumin), micelles and liposomes (SP1049C, NK911, Genexol-PM, CPT-SSM), mesoporous silica nanomaterials, nanosystems (C32/DT-A, PEO-PCL with ceramide + paclitaxel), nanocells (400 nm bacterially derived), dendrimers (DOX-dendrimer), nanotubes/fullerenes (SWCNT, C60, ZME-108 antibody), polymersomes (paclitaxel + DOX), quantum dots (anti-HER2), and XPclad nanoparticles. - XPclad platform: planetary ball milling; biocompatible agents such as alginate, cellulose, starch, or collagen; coating with PEG and/or PCL; targeting molecules (e.g., folate, antibodies, peptides); payloads include drugs, proteins, peptides, nucleic acids, vaccines, and adjuvants. Size ranges reported from 5–30 nm up to 10–60 µm depending on milling parameters, with >99% loading efficiency claimed. - Targeting mechanisms: passive EPR effect, active ligand–receptor targeting, catheter-based local infusion, magnetic targeting, and stimuli-responsive systems (pH, redox, enzymes, physical forces). - Payloads: chemotherapeutics (doxorubicin, paclitaxel, camptothecin, cisplatin), nucleic acids (plasmid DNA, siRNA), proteins/peptides, vaccine antigens, monoclonal antibodies.

Approach: Review of preclinical and clinical literature. In vitro systems include Caco-2 intestinal cells, PC3 prostate cancer cells, RWPE-1 normal prostate epithelial cells, colon carcinoma cells, ovarian cancer cells, melanoma cells, and glioblastoma models. In vivo models include mouse tumor xenografts, rat intestinal loop, and lymphoma in dogs. Clinical examples include approved micelle formulations (SP1049C, NK911, Genexol-PM); nanocell clinical trials were planned. Most discussion is preclinical.

Key methods: Particle size: photon-correlation spectroscopy/dynamic light scattering, SEM/TEM. - Surface properties: zeta potential, hydrophobicity, PEGylation, opsonization. - Drug loading and entrapment efficiency; release kinetics (diffusion cells, dialysis, ultracentrifugation, ultrafiltration). - In vitro cellular uptake and cytotoxicity. - In vivo biodistribution, tumor regression, survival, and toxicity. - Imaging and tracking: MRI with iron oxide, quantum dot tracking.

Key results: 100 nm nanoparticles had 2.5-fold greater uptake than 1 µm microparticles and 6-fold greater uptake than 10 µm microparticles by Caco-2 cells. - DOX-dendrimer was >10 times less toxic than free DOX to colon carcinoma cells in culture; in tumor-bearing mice, tumor uptake was 9-fold higher than intravenous free DOX, causing complete tumor regression and 100% survival after 60 days. - Nanocells delivered drugs at doses ~1000 times lower than free drug for equivalent tumor regression in mouse xenografts and dog lymphoma. - C32/DT-A polymer nanoparticles caused apoptosis in 80% of prostate tumor cells versus 50% of normal prostate cells after a single injection in mice. - Ceramide plus paclitaxel in PEO-PCL nanoparticles completely eradicated multidrug-resistant ovarian cancer cells and resensitized them to paclitaxel near the IC50 of non-MDR cells. - XPclad nanoparticles achieved >99% loading efficiency; folate-coated cisplatin XPclad reduced PC3 tumor regression; dendritic cell-binding peptide XPclad with pneumococcal surface protein A and TLR7/8 adjuvant reduced bacterial load; oral anti-protective antigen mAb XPclad neutralized anthrax toxin after systemic, oral, or respiratory exposure.

Interpretation: Nano delivery systems hold great potential to target diverse cell types, overcome drug resistance, and facilitate movement of drugs across biological barriers such as the blood–brain barrier. XPclad nanoparticles represent a novel formulation method with high loading efficiency, targeted delivery, and controlled release for drugs, proteins, peptides, and nucleic acids. However, precise characterization of molecular targets, ensuring effects only on target organs, and understanding the fate of delivered drugs remain key challenges.

Limitations: Review article; no primary data. - Most cited applications are preclinical; limited clinical validation. - Challenges include precise molecular target characterization, off-target effects, and incomplete understanding of intracellular drug fate after delivery to the nucleus and other organelles. - Nanoparticle stability, aggregation during storage/transport, scale-up, and long-term safety require further study. - XPclad formulation is patented by the authors, representing a potential conflict of interest. - Clinical translation of nanomedicines remains limited by manufacturing, regulatory, and biological barriers.