SWCNTs as novel theranostic nanocarriers for cancer diagnosis and therapy: towards safe translation to the clinics

Size Selective Corona Interactions from Self-Assembled Rosette and Single-Walled Carbon Nanotubes

Nanoparticle corona phases, especially those surrounding anisotropic particles, are central to determining their catalytic, molecular recognition, and interfacial properties. It remains a longstanding challenge to chemically synthesize and control such phases at the nanoparticle surface. In this work, the supramolecular chemistry of rosette nanotubes (RNTs), well-defined hierarchically self-assembled nanostructures formed from heteroaromatic bicyclic bases, is used to create molecularly precise and continuous corona phases on single-walled carbon nanotubes (SWCNTs). These RNT-SWCNT (RS) complexes exhibit the lowest solvent-exposed surface area (147.8 ± 60 m^-1 ) measured to date due to its regular structure. Through Raman spectroscopy, molecular-scale control of the free volume is also observed between the two annular structures and the effects of confined water. SWCNT photoluminescence (PL) within the RNT is also modulated considerably as a function of their diameter and chirality, especially for the (11, 1) species, where a PL increase compared to other species can be attributed to their chiral angle and the RNT's inward facing electron densities. In summary, RNT chemistry is extended to the problem of chemically defining both the exterior and interior corona interfaces of an encapsulated particle, thereby opening the door to precision control of core-shell nanoparticle interfaces.

The Advances in Biomedical Applications of Carbon Nanotubes

Unique chemical, physical, and biological features of carbon nanotubes make them an ideal candidate for myriad applications in industry and biomedicine. Carbon nanotubes have excellent electrical and thermal conductivity, high biocompatibility, flexibility, resistance to corrosion, nano-size, and a high surface area, which can be tailored and functionalized on demand. This review discusses the progress and main fields of bio-medical applications of carbon nanotubes based on recently-published reports. It encompasses the synthesis of carbon nanotubes and their application for bio-sensing, cancer treatment, hyperthermia induction, antibacterial therapy, and tissue engineering. Other areas of carbon nanotube applications were out of the scope of this review. Special attention has been paid to the problem of the toxicity of carbon nanotubes.

Effect of polyethylene glycol surface charge functionalization of SWCNT on the in vitro and in vivo nanotoxicity and biodistribution monitored noninvasively using MRI

The current study evaluated in vitro and in vivo toxicity of carboxyl or amine polyethylene glycol (PEG) surface functionalization of single-walled carbon nanotubes (SWCNTs). Assessments of cytotoxicity, genotoxicity, immunotoxicity, and oxidative stress were performed in vitro and in vivo (in a 1-month follow-up study). The SWCNT biodistribution was investigated using noninvasive magnetic resonance imaging (MRI). Results confirmed the enhanced biocompatibility of PEG-functionalized SWCNTs compared to non-functionalized materials with significant decreases (p < 0.05) in the percentage of cell viability and increases in ROS generation, mitochondrial membrane potential, cell apoptosis, oxidative stress generation, and oxidative DNA damage in vitro. PEG-functionalized SWCNTs with amine terminals were found to induce prominent increases in ROS generation, mitochondrial membrane potential, and oxidative stress compared to carboxy functionalization. No significant difference in the biodistribution of either functionalized SWCNTs was observed in MRI. In vivo assessments revealed a statistically significant increase (p < 0.05) in oxidative stress as early as 24 h in serum and liver; however, all values normalized at 2 weeks' investigation time point. DNA damage was minimal with either PEG-COOH or PEG-NH₂ functionalized SWCNTs after 2 weeks' exposure. The negatively charged SWCNTs caused lesser DNA damage compared to positively charged samples. Carboxy-functionalized SWCNTs did not cause substantial changes in inflammatory mediators and were found to be significantly safer than non-functionalized SWCNTs and may pave the way for novel biomedical applications in cancer diagnosis and therapy.

Enzymatically Partially Hydrolyzed α-Lactalbumin Peptides for Self-Assembled Micelle Formation and Their Application for Coencapsulation of Multiple Antioxidants

The codelivery system for multiple antioxidants such as anthocyanins (Ant) and curcumin (Cur) of synergistic action may effectively enhance their stability and cellular absorption. We have reported that amphiphilic peptides obtained from enzymatic partial hydrolysis of α-lactalbumin (α-lac) can self-assemble into 20 nm monodispersed nanomicelles in aqueous solution. Cur and Ant could be coloaded into the micelles sequentially via hydrophobic and electrostatic interactions, which was proved by fluorescence quenching experiments for the Cur-micelle and Ant-micelle interactions. Circular dichroism spectra proved that the Cur and Ant binding did not affect their structure confirmation. Both Cur- and Ant-loaded micelles showed improved stability and also exhibited an intestinal pH responsive release property in simulated gastrointestinal fluid. In addition, the nanomicelles exhibited an advanced cellular uptake and transmembrane permeability based on Caco-2 cell monolayer models. Finally, the coloaded micelles possessed a synergistic efficiency such that cellular antioxidant activity (CAA) for Cur and Ant was markedly improved.

Multifunctional Dendrimer-Entrapped Gold Nanoparticles Conjugated with Doxorubicin for pH-Responsive Drug Delivery and Targeted Computed Tomography Imaging

Novel theranostic nanocarriers exhibit a desirable potential to treat diseases based on their ability to achieve targeted therapy while allowing for real-time imaging of the disease site. Development of such theranostic platforms is still quite challenging. Herein, we present the construction of multifunctional dendrimer-based theranostic nanosystem to achieve cancer cell chemotherapy and computed tomography (CT) imaging with targeting specificity. Doxorubicin (DOX), a model anticancer drug, was first covalently linked onto the partially acetylated poly(amidoamine) dendrimers of generation 5 (G5) prefunctionalized with folic acid (FA) through acid-sensitive cis-aconityl linkage to form G5·NHAc-FA-DOX conjugates, which were then entrapped with gold (Au) nanoparticles (NPs) to create dendrimer-entrapped Au NPs (Au DENPs). We demonstrate that the prepared DOX-Au DENPs possess an Au core size of 2.8 nm, have 9.0 DOX moieties conjugated onto each dendrimer, and are colloid stable under different conditions. The formed DOX-Au DENPs exhibit a pH-responsive release profile of DOX because of the cis-aconityl linkage, having a faster DOX release rate under a slightly acidic pH condition than under a physiological pH. Importantly, because of the coexistence of targeting ligand FA and Au core NPs as a CT imaging agent, the multifunctional DOX-loaded Au DENPs afford specific chemotherapy and CT imaging of FA receptor-overexpressing cancer cells. The constructed DOX-conjugated Au DENPs hold a promising potential to be utilized for simultaneous chemotherapy and CT imaging of various types of cancer cells.

Hydrophobic IR-780 Dye Encapsulated in cRGD-Conjugated Solid Lipid Nanoparticles for NIR Imaging-Guided Photothermal Therapy

This is high demand to enhance the accumulation of near-infrared theranostic agents in the tumor region, which is favorable to the effective phototherapy. Compared with indocyanine green (a clinically applied dye), IR-780 iodide possesses higher and more stable fluorescence intensity and can be utilized as an imaging-guided PTT agent with laser irradiation. However, lipophilicity and short circulation time limit its applications in cancer imaging and therapy. Moreover, solid lipid nanoparticles (SLNs) conjugated with c(RGDyK) was designed as efficient carriers to improve the targeted delivery of IR-780 to the tumors. The multifunctional cRGD-IR-780 SLNs exhibited a desirable monodispersity, preferable stability and significant targeting to cell lines overexpressing α_vβ₃ integrin. Additionally, the in vitro assays such as cell viability and in vivo PTT treatment denoted that U87MG cells or U87MG transplantation tumors could be eradicated by applying cRGD-IR-780 SLNs under laser irradiation. Therefore, the resultant cRGD-IR-780 SLNs may serve as a promising NIR imaging-guided targeting PTT agent for cancer therapy.

Carbon Nanotubes as an Effective Opportunity for Cancer Diagnosis and Treatment

Despite the current progresses of modern medicine, the resistance of malignant tumors to present medical treatments points to the necessity of developing new therapeutic approaches. In recent years, numerous studies have focused their attention on the promising use of nanomaterials, like iron oxide nanowires, zinc oxide or mesoporous silica nanoparticles, for cancer and metastasis treatment with the advantage of operating directly at the bio-molecular scale. Among them, carbon nanotubes emerged as valid candidates not only for drug delivery, but also as a valuable tool in cancer imaging and physical ablation. Nevertheless, deep investigations about carbon nanotubes' potential bio-compatibility and cytotoxicity limits should be also critically addressed. In the present review, after introducing carbon nanotubes and their promising advantages and drawbacks for fighting cancer, we want to focus on the numerous and different ways in which they can assist to reach this goal. Specifically, we report on how they can be used not only for drug delivery purposes, but also as a powerful ally to develop effective contrast agents for tumors' medical or photodynamic imaging, to perform direct physical ablation of metastasis, as well as gene therapy.

Polyethylenimine-functionalized carbon nanotubes tagged with AS1411 aptamer for combination gene and drug delivery into human gastric cancer cells

In this project, synergistic cancer cell death was achieved by a targeted delivery system comprising Bcl-xL-specific shRNA and a very low DOX content, which simultaneously activated an intrinsic apoptotic pathway. A modified branched polyethylenimine (PEI 10kDa) was grafted through polyethylene glycol (PEG) linker to carboxylated single-walled carbon nanotubes (SWCNT) to serve as a vehicle for shRNA delivery. The SWNT-PEG-PEI conjugate was covalently attached to AS1411 aptamer as the nucleolin ligand to target the co-delivery system to the tumor cells overexpressing nucleolin receptors on their surface. The final vehicle was eventually obtained after intercalation of DOX with pBcl-xL shRNA-SWCNT-PEG-10-10%PEI-Apt. Cell viability assay, GFP expression and transfection experiment against L929 (-nucleolin) and AGS (+nucleolin) cells illustrated that the tested targeted delivery system inhibited the growth of nucleolin-abundant gastric cancer cells with strong cell selectivity. Subsequently, we illustrated that the combination treatment of the selected shRNAs and DOX had excellent tumoricidal efficacy as verified by MTT assay. Furthermore, very low concentration of DOX, approximately 58-fold lower than its IC50 concentration, was used which could mitigate toxic side effects of DOX. Overall, our work revealed that combination of shRNA-mediated gene-silencing strategy with chemotherapeutic agents constitutes a valuable and safe approach for antitumor activity.