Synthesis, self-assembly and drug release behaviors of a bottlebrush polymer-HCPT prodrug for tumor chemotherapy

Enzyme-triggered transcytosis of drug carrier system for deep penetration into hepatoma tumors

In recent years, nano-drug delivery systems have made considerable progress in the direction of tumor treatment, but the low permeability of drugs has restricted the development of nano drugs. To solve this problem, we constructed a nano-drug delivery system with the dual effects of γ-glutamyltransferase (GGT) reaction and high nuclear targeting in tumor microenvironment to promote the deep penetration of drugs. Over-expression of GGT in tumor cells can specifically recognize γ-glutamyl substrate and release amino group from the hydrolysis reaction, which makes the whole system change from negative or neutral to positive charge system. The conjugated complex with positive charge rapidly endocytosis through electrostatic interaction, enhancing its permeability in tumor parenchyma. At the same time, the cell penetrating TAT contains a large amount of lysine, which can be identified by the nuclear pore complexes (NPCs) on the surface of the nuclear membrane, showing excellent nuclear localization function. The active DOX is released in the nucleus, which inhibits the mitosis of cancer cells and enhances the active transport ability of drugs in tumor cells. Therefore, this drug delivery system actively transports adriamycin into the tumor to achieve deep penetration of drugs through enzyme response and nuclear targeting, showing high anti-tumor activity and can be effectively applied to the treatment of liver cancer.

Structure modification: a successful tool for prodrug design

Prodrug strategy is critical for innovative drug development. Structural modification is the most straightforward and effective method to develop prodrugs. Improving drug defects and optimizing the physical and chemical properties of a drug, such as lipophilicity and water solubility, changing the way of administration can be achieved through specific structural modification. Designing prodrugs by linking microenvironment-responsive groups to the prototype drugs is of great help in enhancing drug targeting. In the meantime, making connections between prodrugs and suitable drug delivery systems could realize drug loading increases, greater stability, bioavailability and drug release control. In this paper, lipidic, water-soluble, pH-responsive, redox-sensitive and enzyme-activatable prodrugs are reviewed on the basis of structural modification.

Advances in Antitumor Nano-Drug Delivery Systems of 10-Hydroxycamptothecin

10-Hydroxycamptothecin (HCPT) is a natural plant alkaloid from Camptotheca that shows potent antitumor activity by targeting intracellular topoisomerase I. However, factors such as instability of the lactone ring and insolubility in water have limited the clinical application of this drug. In recent years, unprecedented advances in biomedical nanotechnology have facilitated the development of nano drug delivery systems. It has been found that nanomedicine can significantly improve the stability and water solubility of HCPT. NanoMedicines with different diagnostic and therapeutic functions have been developed to significantly improve the anticancer effect of HCPT. In this paper, we collected reports on HCPT nanomedicines against tumors in the past decade. Based on current research advances, we dissected the current status and limitations of HCPT nanomedicines development and looked forward to future research directions.

Molecular bottlebrush with pH-responsive cleavable bonds as a unimolecular vehicle for anticancer drug delivery

Drug delivery systems with targeted and smart properties have emerged as an efficient strategy to overcome the challenges of cancer chemotherapy such as toxic side effects and the development of multidrug resistance. In this study, a biocompatible bottlebrush polymer poly((3-(2-bromo-2-methylpropionate)propyldimethylsilyloxy)ethyl methacrylate)-graft-poly(2-methacryloyloxyethyl phosphorylcholine) P(BIBS-EMA)-g-PMPC with pH-responsive silanol cleavable bond was designed and developed for delivery of doxorubicin. A549 cell line of human lung carcinoma was tested. The synthesized bottlebrush polymer was analyzed and characterized via Fourier transform infrared spectroscopy, FTIR, nuclear magnetic resonance spectroscopy, ¹H NMR, gel permeation chromatography, GPC, dynamic laser light scattering, DLS, and static laser light scattering, SLS, techniques. The cleavage process was also precisely studied to confirm the pH-responsiveness of such bottlebrush polymers. In vitro loading and release studies of doxorubicin as a model drug were examined and the results showed a pH-dependent release manner with a twice higher release rate under cancerous tissue conditions compared to standard physiological conditions. MTT cytotoxicity assay was also performed to prove the biocompatibility of the designed polymeric platform on healthy human cells. Due to the presence of bio-inspired poly(2-methacryloyloxyethyl phosphorylcholine) side chains in the prepared bottlebrush polymer, the formed polymer-drug complex could also exhibit effective internalization into tumor cells. These facts further support the potential use of this carrier in drug delivery applications and for further in vivo studies.

Transferrin-conjugated liposomes loaded with carnosic acid inhibit liver cancer growth by inducing mitochondria-mediated apoptosis

Our previous studies have proven that carnosic acid (CA) induces apoptosis of liver cancer cells. However, the poor chemical properties of CA limit its in vivo anti-cancer effects. In this study, CA was loaded into liposomes (LP-CA), and LP-CA was further conjugated with transferrin (Tf-LP-CA) to overcome the shortcomings of poor solubility and absorption at the lesion site. In HepG2 and SMMC-7721 cells, compared with CA and LP-CA, more Tf-LP-CA was absorbed by liver cancer cells, which induced higher levels of apoptosis and reduced the mitochondrial membrane potential more effectively. In HepG2- and SMMC-7721-xenotransplanted mice, Tf-LP-CA inhibited tumor growth with no cytotoxicity to the liver, spleen, or kidney. Furthermore, compared with CA and LP-CA, Tf-LP-CA targeted the tumor site more effectively, enhanced the expressions of cleaved poly(ADP-ribose) polymerase, and Caspase-3 and -9, and regulated the expression levels of B-cell lymphoma 2 (Bcl2) family members in the tumor tissues. Tf-LP-CA was taken up by tumor cells and targeted at tumor tissues, ensuring the precise delivery of CA, which further promoted mitochondria-mediated intrinsic apoptosis in the liver cancer cells. These results provide evidence for the clinical application of the Tf-LP-based CA drug delivery system for liver cancer.

Bottlebrush Polymer Excipients Enhance Drug Solubility: Influence of End-Group Hydrophilicity and Thermoresponsiveness

Bottlebrush polymers have great potential as vehicles to noncovalently sequester, stabilize, and deliver hydrophobic small molecule actives. To this end, we synthesized a poly(N-isopropylacrylamide-stat-N,N-dimethylacrylamide) bottlebrush copolymer using ring-opening metathesis polymerization and developed a facile method to control the thermoresponsive properties using postpolymerization modification. Six increasingly hydrophilic end-groups were installed, yielding cloud point temperature control over a range of 22-42 °C. Solubility enhancement of the antiseizure medication, phenytoin, increased significantly with the hydrophilicity of the end-group moiety. Notably, carboxylated bottlebrush copolymers solubilized formulations with higher drug loadings than linear copolymers because they exist as unimolecular nanoparticles with a synthetically defined density of polymer chains that are more stable in solution. This work provides the first investigation of bottlebrush polymers for hydrophobic noncovalent sequestration and solubilization of pharmaceuticals.

Recent developments in natural and synthetic polymeric drug delivery systems used for the treatment of osteoarthritis

Osteoarthritis (OA), is a common musculoskeletal disorder that will progressively increase in older populations and is expected to be the most dominant cause of disability in the world population by 2030. The progression of OA is controlled by a multi-factorial pathway that has not been completely elucidated and understood yet. However, over the years, research efforts have provided a significant understanding of some of the processes contributing to the progression of OA. Both cartilage and bone degradation processes induce articular cells to produce inflammatory mediators that produce proinflammatory cytokines that block the synthesis of collagen type II and aggrecan, the major components of cartilage. Systemic administration and intraarticular injection of anti-inflammatory agents are the first-line treatments of OA. However, small anti-inflammatory molecules are rapidly cleared from the joint cavity which limits their therapeutic efficacy. To palliate this strong technological drawback, different types of polymeric materials such as microparticles, nanoparticles, and hydrogels, have been examined as drug carriers for the delivery of therapeutic agents to articular joints. The main purpose of this review is to provide a summary of recent developments in natural and synthetic polymeric drug delivery systems for the delivery of anti-inflammatory agents to arthritic joints. Furthermore, this review provides an overview of the design rules that have been proposed so far for the development of drug carriers used in OA therapy. Overall it is difficult to state clearly which polymeric platform is the most efficient one because many advantages and disadvantages could be pointed to both natural and synthetic formulations. That requires further research in the near future.

Lysine-mediated hydroxyethyl starch-10-hydroxy camptothecin micelles for the treatment of liver cancer

Liver cancer is a malignant tumor with extremely high morbidity and mortality. At present, traditional chemotherapy is still the most commonly used therapeutic approach. However, serious side effects lead to the treatment of liver cancer is not ideal. Therefore, it is imperative to develop a new drug delivery system based on nanotechnology and liver cancer microenvironment. In this study, a pH/reduction/α-amylase multi-sensitive hydroxyethyl starch-10-hydroxy camptothecin micelles (HES-10-HCPT-SS-Ly) targeting over-expressed amino acid (AA) transporters on the surface of liver cancer cell by applying lysine were successfully synthesized. The prepared micelles showed regular structure, suitable particle size, and intelligent drug release property. Compared with conventional HES-10-HCPT micelles and 10-HCPT injection, HES-10-HCPT-SS-Ly micelles demonstrated better in vitro anti-proliferative capability toward human liver cancer Hep-G2 cells and greater antitumor efficiency against nude mouse with Hep-G2 tumor. These findings suggest that HES-10-HCPT-SS-Ly micelles may be a promising nanomedicine for treatment of liver cancer.

Advances and perspectives in carrier-free nanodrugs for cancer chemo-monotherapy and combination therapy

Nanocarrier-based drug delivery systems hold impressive promise for biomedical application because of their excellent water dispersibility, prolonged blood circulation time, increased drug accumulation in tumors, and potential in combination therapeutics. However, most nanocarriers suffer from low drug-loading efficiency, poor therapeutic effectiveness, potential systematic toxicity, and unstable metabolism. As an alternative, carrier-free nanodrugs, completely formulated with one or more drugs, have attracted increasing attention in cancer therapy due to their advantage of improved pharmacodynamics/pharmacokinetics, reduced toxicity, and high drug-loading. In recent years, carrier-free nanodrugs have contributed to progress in a variety of therapeutic modalities. In this review, different common strategies for carrier-free nanodrugs preparation are first summarized, mainly including nanoprecipitation, template-assisted nanoprecipitation, thin-film hydration, spray-drying technique, supercritical fluid (SCF) technique, and wet media milling. Then we describe the recently reported carrier-free nanodrugs for cancer chemo-monotherapy or combination therapy. The advantages of anti-cancer drugs combined with other chemotherapeutic, photosensitizers, photothermal, immunotherapeutic or gene drugs have been demonstrated. Finally, a future perspective is introduced to highlight the existing challenges and possible solutions toward clinical application of currently developed carrier-free nanodrugs, which may be instructive to the design of effective carrier-free regimens in the future.

Enhanced Stability of the Pharmacologically Active Lactone Form of 10-Hydroxycamptothecin by Self-Microemulsifying Drug Delivery Systems

10-Hydroxycamptothecin (HCPT) is a DNA inhibitor of topoisomerase I and exerts antitumor activities against various types of cancer. However, reversible conversion from a pharmacologically active lactone form to an inactive carboxylate form of HCPT and poor water solubility hamper its clinical applications. To overcome these shortcomings, we designed a fine self-microemulsifying drug delivery system (SMEDDS) for HCPT to effectively protect HCPT in its active lactone form as well as improving dissolution rates. A formulation of HCPT-SMEDDS that contained ethyl oleate, D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), and polyethylene glycol 400 (PEG400) was optimized by using the central composite design and response surface methodology. Following 1:100 aqueous dilution of the optimized HCPT-SMEDDS, the droplet size of resulting microemulsions was 25.6 ± 0.7 nm, and the zeta potential was - 15.2 ± 0.4 mV. The optimized HCPT-SMEDDS appeared to stabilize the lactone moiety of HCPT with 73.6% being present in the pharmacologically active lactone forms in simulated intestinal fluid, but only 45.7% for free HCPT. Furthermore, the physically stable formulation showed the active lactone form predominated in HCPT-SMEDDS (> 95%) for 6 months under the accelerated storage condition. Meanwhile, the optimized SMEDDS formulation also significantly improved dissolution rates and membrane permeability of the lactone form of HCPT. Therefore, HCPT-SMEDDS involved designing for the ease of manufacture, and provided a potent oral dosage form for preserving its active lactone form as well as enhancing the dissolution rate.

Liposomes modified with bio-substances for cancer treatment

In recent years, liposomes have been used in the field of biomedicine and have achieved many significant results.