Nuclear Drug Delivery Research Articles

Nuclear Pore Complex: From Structural View to Chemical Tools

Nuclear pore complexes (NPCs) are the macromolecular turnstiles between the cytoplasm and the nucleus that control the trafficking of proteins, RNAs and viruses. The giant NPC structures are extremely complex. Here, I highlight several recent findings on NPC architectures, and briefly discuss how chemical biologists might use this information to design synthetic devices and improve strategies for nuclear drug delivery.

A smart polymeric platform for multistage nucleus-targeted anticancer drug delivery

Tumor cell nucleus-targeted delivery of antitumor agents is of great interest in cancer therapy, since the nucleus is one of the most frequent targets of drug action. Here we report a smart polymeric conjugate platform, which utilizes stimulus-responsive strategies to achieve multistage nuclear drug delivery upon systemic administration. The conjugates composed of a backbone based on N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer and detachable nucleus transport sub-units that sensitive to lysosomal enzyme. The sub-units possess a biforked structure with one end conjugated with the model drug, H1 peptide, and the other end conjugated with a novel pH-responsive targeting peptide (R8NLS) that combining the strength of cell penetrating peptide and nuclear localization sequence. The conjugates exhibited prolonged circulation time and excellent tumor homing ability. And the activation of R8NLS in acidic tumor microenvironment facilitated tissue penetration and cellular internalization. Once internalized into the cell, the sub-units were unleashed for nuclear transport through nuclear pore complex. The unique features resulted in 50-fold increase of nuclear drug accumulation relative to the original polymer–drug conjugates in vitro, and excellent in vivo nuclear drug delivery efficiency. Our report provides a strategy in systemic nuclear drug delivery by combining the microenvironment-responsive structure and detachable sub-units.

Dual-pH Sensitive Charge-Reversal Polypeptide Micelles for Tumor-Triggered Targeting Uptake and Nuclear Drug Delivery.

A novel dual-pH sensitive charge-reversal strategy is designed to deliver antitumor drugs targeting to tumor cells and to further promote the nuclei internalization by a stepwise response to the mildly acidic extracellular pH (≈6.5) of a tumor and endo/lysosome pH (≈5.0). Poly(L-lysine)-block-poly(L-leucine) diblock copolymer is synthesized and the lysine amino residues are amidated by 2,3-dimethylmaleic anhydride to form β-carboxylic amide, making the polypeptides self-assemble into negatively charged micelles. The amide can be hydrolyzed when exposed to the mildly acidic tumor extracellular environment, which makes the micelles switch to positively charged and they are then readily internalized by tumor cells. A nuclear targeting Tat peptide is further conjugated to the polypeptide via a click reaction. The Tat is amidated by succinyl chloride to mask its positive charge and cell-penetrating function and thus to inhibit nonspecific cellular uptake. After the nanoparticles are internalized into the more acidic intracellular endo/lysosomes, the Tat succinyl amide is hydrolyzed to reactivate the Tat nuclear targeting function, promoting nanoparticle delivery into cell nuclei. This polypeptide nanocarrier facilitates tumor targeting and nuclear delivery simultaneously by simply modifying the lysine amino residues of polylysine and Tat into two different pH-sensitive β-carboxylic amides.

Overcoming multidrug resistance of cancer cells by direct intranuclear drug delivery using TAT-conjugated mesoporous silica nanoparticles

The development of multidrug resistance (MDR) in cancer cells is one of major obstacles to the effective cancer chemotherapy. In this report we demonstrate the effective circumvention of multidrug resistance in cancer cells by an active nuclear-targeted drug delivery system that was constructed by conjugating TAT peptide onto the surface of mesoporous silica nanoparticles (MSNs-TAT). The conjugation of TAT peptide facilitated the intranuclear localization of MSNs-TAT and the release of the encapsulated drugs directly within the nucleoplasm. The direct intranuclear drug delivery of doxorubicin (DOX) in multidrug resistant MCF-7/ADR cancer cells was capable of increasing the intracellular as well as intranuclear drug concentrations much more effectively than free DOX or delivered by MSNs in the absence of TAT peptide. With the nuclear drug delivery fashion, DOX-MSNs-TAT presents a promising strategy in overcoming MDR in cancer cells and improving the therapeutic index of currently available chemotherapeutics by enhancing therapeutic efficacy and reducing side effects.

Nuclear drug delivery for cancer chemotherapy

Nanosystems with unique physical and biological properties have been extensively explored for cancer targeted intracellular delivery of small-molecular chemotherapeutic drugs to increase their therapeutic efficacies and to minimize their side effects. A large number of anticancer drugs are DNA-toxins that bind nuclear DNA or its associated enzymes to exert their cytotoxicity to cancer cells. After entering tumor cells, they need to be further delivered to the nucleus for actions. Herein, we discuss the biological barriers and summarize recent progress of nuclear drug delivery for cancer chemotherapy, emphasizing strategies that appear useful for design of vehicles capable of delivering drugs to the nucleus, particularly for in vivo applications. The existing obstacles or problems that need to be overcome before successful applications of nuclear drug delivery for cancer chemotherapy are also discussed.

Linear polyethyleneimine-based charge-reversal nanoparticles for nuclear-targeted drug delivery

Cationic polymer polyethyleneimine (PEI) can carry DNA across the cell membrane and enter the nucleus, and thus can be a very useful carrier for nuclear drug delivery; however, its highly positive charges make it toxic and not applicable for systemic drug delivery. Here, well-defined linear PEI (Mn = 1000 or 1500 or 2000)-block-polycaprolactone (Mn = 2000) (LPEI–PCL) was synthesized and used to fabricate a pH-triggered charge-reversal nanoparticle to solve this problem. LPEI's secondary amines are amidized as acid-labile β-carboxylic amides (LPEI/amide–PCL). LPEI/amide–PCL formed negatively charged nanoparticles with very low toxicity and low interaction with cells. Once in an acidic environment, the amides hydrolyze to regenerate the amine groups, producing LPEI–PCL nanoparticles carrying cationic charges. The LPEI–PCL escapes from the lysosomes and traverses into the nucleus. Folic-acid targeting groups are introduced to render the nanoparticles cancer-cell targeting capability. The nanoparticles efficiently enter folate-receptor overexpressing cancer cells and traverse to their nuclei. The DOX loaded in the carrier shows much improved cytotoxicity to cancer cells.

Charge-Reversal Polyamidoamine Dendrimer for Cascade Nuclear Drug Delivery

Polyamidoamine (PAMAM) dendrimers with primary amine termini have been extensively explored as drug and gene carriers owing to their unique properties, but their amine-carried cationic charges cause nonspecific cellular uptakes, systemic toxicity and other severe problems in in vivo applications. In this article, we report a charge-reversal approach that latently deactivates PAMAM's primary amines to negatively charged acid-labile amides in order to inhibit its nonspecific interaction with cells, but regenerates the active PAMAM once in acidic environments. A cascade cancer cell nuclear drug delivery was achieved using the latently amidized PAMAM as the carrier conjugated with folic acid as the targeting group and a DNA-toxin drug camptothecin. The conjugate had low nonspecific interactions with cells, but easily entered cancer cells overexpressing folate receptors via receptor-mediated endocytosis. Subsequently, the endocytosed conjugate was transferred to acidic lysosomes, wherein the active PAMAM carrier was regenerated, escaped from the lysosome and then entered the nucleus for drug release. This reversible deactivation/activation makes PAMAM dendrimers useful nanocarriers for in vivo cancer cell nuclear-targeted drug delivery.

Charge‐Reversal Drug Conjugate for Targeted Cancer Cell Nuclear Drug Delivery

AbstractDNA‐toxin anticancer drugs target nuclear DNA or its associated enzymes to elicit their pharmaceutical effects, but cancer cells have not only membrane‐associated but also many intracellular drug‐resistance mechanisms that limit their nuclear localization. Thus, delivering such drugs directly to the nucleus would bypass the drug‐resistance barriers. The cationic polymer poly(L‐lysine) (PLL) is capable of nuclear localization and may be used as a drug carrier for nuclear drug delivery, but its cationic charges make it toxic and cause problems in in‐vivo applications. Herein, PLL is used to demonstrate a pH‐triggered charge‐reversal carrier to solve this problem. PLL's primary amines are amidized as acid‐labile β‐carboxylic amides (PLL/amide). The negatively charged PLL/amide has a very low toxicity and low interaction with cells and, therefore, may be used in vivo. But once in cancer cells' acidic lysosomes, the acid‐labile amides hydrolyze into primary amines. The regenerated PLL escapes from the lysosomes and traverses into the nucleus. A cancer‐cell targeted nuclear‐localization polymer–drug conjugate has, thereby, been developed by introducing folic‐acid targeting groups and an anticancer drug camptothecin (CPT) to PLL/amide (FA‐PLL/amide‐CPT). The conjugate efficiently enters folate‐receptor overexpressing cancer cells and traverses to their nuclei. The CPT conjugated to the carrier by intracellular cleavable disulfide bonds shows much improved cytotoxicity.

Dendrimer-based tumor cell targeting of fibroblast growth factor-1

Fibroblast Growth Factor Receptor (FGFR) is overexpressed in a wide variety of tumors, and therefore is an attractive target for drug delivery. Recombinant FGF-1 was purified and attached to a fifth-generation (G5) polyamidoamine dendrimer. The specific binding and internalization of this conjugate labeled with FITC was demonstrated by flow cytometry as well as by confocal microscopic analysis in cell lines expressing FGFR. The binding and uptake of FGF-conjugated dendrimers was completely blocked by excess nonconjugated FGF-1. Confocal microscopic analysis showed cytosolic as well as nuclear localization. Multivalent G5-FGF nanoparticles may serve as a platform for cytosolic as well as nuclear drug delivery in tumor cells, and as an FGF delivery agent for angiogenesis and wound healing. Our study shows for the first time the applicability of a dendrimer nanodevice for tumor cell targeting through FGFR.

Nuclear Localization of Cell-Penetrating Peptides Is Dependent on Endocytosis Rather Than Cytosolic Delivery in CHO Cells

The nuclear localization of various cell penetrating peptides (CPPs), including Tat [47-57], YG(R)9, YG(K)9, and model amphipathic peptide (MAP), was examined and correlated with the endocytosis and cytosolic transfer efficiency in CHO cells. The results showed that the internalization of the amphipathic peptide, MAP, was much higher than that of the other cationic CPPs tested. During subcellular fractionation analysis, MAP was only found in the vesicular fraction and was not detectable in the cytosol, similar to the intracellular localization of YG(K)9 as previously determined. This localization pattern differs greatly from the cationic CPPs oligoarginine and Tat, which were previously found primarily in the cytosol. Both quantitative and qualitative analysis of MAP showed high nuclear localization, with staining in perinuclear vesicles. On the other hand, YG(R)9 was found to be excluded from the nucleus. Lysosomotropic amines altered the nuclear localization of the CPPs tested, and the change was correlated with the release of degradation products from the treated cells. These results suggest that highly endocytosed CPPs such as MAP may be more suitable for nuclear drug delivery applications than peptides such as Tat and YG(R)9 that are efficiently delivered to the cytosol.

Targeted Charge‐Reversal Nanoparticles for Nuclear Drug Delivery

Ladungsumkehr: Nanopartikel aus Poly(ε-caprolacton)-block-polyethylenimin (PCL-PEI) mit in Amide überführten Amingruppen, deren Ladung gezielt geändert werden kann (TCRNs), sind bei neutralem pH-Wert negativ geladen, bei pH<6 dagegen positiv (siehe Bild). Solche TCRNs treten leicht in Zellen ein, regenerieren die PEI-Schicht in Lysosomen und wandern in den Kern zur Wirkstoffabgabe.

Targeted Charge‐Reversal Nanoparticles for Nuclear Drug Delivery

Targeted Charge‐Reversal Nanoparticles for Nuclear Drug Delivery

29. Synthetic and bioengineered products in nuclear medicine and drug delivery

29. Synthetic and bioengineered products in nuclear medicine and drug delivery