Doxorubicin-doxorubicin conjugate prodrug as drug self-delivery system for intracellular pH-triggered slow release

Regulating Drug Release Performance of Acid-Triggered Dimeric Prodrug-Based Drug Self-Delivery System by Altering Its Aggregation Structure

Dimeric prodrugs have been investigated intensely as carrier-free drug self-delivery systems (DSDSs) in recent decades, and their stimuli-responsive drug release has usually been controlled by the conjugations between the drug molecules, including the stimuli (pH or redox) and responsive sensitivity. Here, an acid-triggered dimeric prodrug of doxorubicin (DOX) was synthesized by conjugating two DOX molecules with an acid-labile ketal linker. It possessed high drug content near the pure drug, while the premature drug leakage in blood circulation was efficiently suppressed. Furthermore, its aggregation structures were controlled by fabricating nanomedicines via different approaches, such as fast precipitation and slow self-assembly, to regulate the drug release performance. Such findings are expected to enable better anti-tumor efficacy with the desired drug release rate, beyond the molecular structure of the dimeric prodrug.

A glutathione-responsive PEGylated nanogel with doxorubicin-conjugation for cancer therapy

The complexity, degradability, and stability of drug delivery systems are crucial factors for clinical application. Herein, a glutathione (GSH)-responsive polyethylene glycol (PEG)ylated nanogel conjugated with doxorubicin (Dox) was prepared based on a linker with disulfide bonds, PEG, and Dox using a one-pot method. FT-IR and UV-vis analyses confirmed that all raw materials were incorporated in the Dox-conjugated nanogel structure. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) results showed that the particle size of the Dox-conjugated nanogel was at the nanoscale and could be responsively disrupted in high GSH concentration. The in vitro accumulative Dox release rate from the nanogel reached 88% in PBS with 5 mg mL-1 GSH on day 4. Moreover, H22 cell viability and apoptosis experiments revealed that the nanogel effectively inhibited tumor cell growth. In vivo tracking and cell uptake experiments demonstrated that the nanogel accumulated and persisted in tumor tissues for 5 days and was distributed into cell nuclei at 6 h. Furthermore, H22-bearing mice experiments showed that the tumor size of the Dox-conjugated nanogel group was the smallest (287 mm3) compared to that of the free Dox (558 mm3) and 0.9% NaCl (2700 mm3) groups. Meanwhile, the body weight of mice as well as the H&E and TUNEL tissue section staining of organs and tumor tissues from the mice illustrated that the nanogel could significantly prevent side effects and induce tumor cell apoptosis. Taken together, compared with free Dox, the Dox-conjugated nanogel exhibited higher therapeutic efficacy and lower side effects in normal tissues, making it a potential novel nanomedicine for cancer.

Preparation of metal-organic framework combined with Portulaca oleracea L. extract electrostatically spun nanofiber membranes delayed release wound dressing

In this study, we prepared a polyacrylonitrile (PAN) composite nanofiber membrane comprising Portulaca oleracea L. extract (POE) and a zinc-based metal-organic framework (MOF) by an in situ growth method as a potentially new type of wound dressing with a slow drug-release effect, to solve the problem of the burst release of drugs in wound dressings. The effects of the MOF and POE doping on the nanofiber membranes were examined using scanning electron microscopy (SEM) and FTIR spectroscopy. SEM analysis revealed the dense and uniform attachment of MOF particles to the surface of the nanofiber membrane, while FTIR spectroscopy confirmed the successful fusion of MOF and POE. Furthermore, investigations into the water contact angle and swelling property demonstrated that the incorporation of the MOF and POE enhanced the hydrophilicity of the material. The results of the in vitro release test showed that the cumulative release rate for PAN/MOF/POE60 decreased from 66.5 ± 2.34% to 32.18 ± 1.31% in the initial 4 h and from 90.54 ± 0.79% to 65.92 ± 1.95% in 72 h compared to PAN/POE, indicating a slowing down of the drug release. In addition, the antimicrobial properties of the fiber membranes were evaluated by the disc diffusion method, and it was evident that the PAN/MOF/POE nanofibers exhibited strong inhibition against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The antioxidant properties of the nanofiber membranes loaded with POE were further validated through the DPPH radical scavenging test. These findings highlight the potential application of the developed nanofiber membranes in wound dressings, offering controlled and sustained drug-release capabilities.

A 3D Tumor-Mimicking In Vitro Drug Release Model of Locoregional Chemoembolization Using Deep Learning-Based Quantitative Analyses

Primary liver cancer, with the predominant form as hepatocellular carcinoma (HCC), remains a worldwide health problem due to its aggressive and lethal nature. Transarterial chemoembolization, the first-line treatment option of unresectable HCC that employs drug-loaded embolic agents to occlude tumor-feeding arteries and concomitantly delivers chemotherapeutic drugs into the tumor, is still under fierce debate in terms of the treatment parameters. The models that can produce in-depth knowledge of the overall intratumoral drug release behavior are lacking. This study engineers a 3D tumor-mimicking drug release model, which successfully overcomes the substantial limitations of conventional in vitro models through utilizing decellularized liver organ as a drug-testing platform that uniquely incorporates three key features, i.e., complex vasculature systems, drug-diffusible electronegative extracellular matrix, and controlled drug depletion. This drug release model combining with deep learning-based computational analyses for the first time permits quantitative evaluation of all important parameters associated with locoregional drug release, including endovascular embolization distribution, intravascular drug retention, and extravascular drug diffusion, and establishes long-term in vitro-in vivo correlations with in-human results up to 80 d. This model offers a versatile platform incorporating both tumor-specific drug diffusion and elimination settings for quantitative evaluation of spatiotemporal drug release kinetics within solid tumors.

Research Progress of Conjugated Nanomedicine for Cancer Treatment

The conventional cancer therapeutic modalities include surgery, chemotherapy and radiotherapy. Although immunotherapy and targeted therapy are also widely used in cancer treatment, chemotherapy remains the cornerstone of tumor treatment. With the rapid development of nanotechnology, nanomedicine is believed to be an emerging field to further improve the efficacy of chemotherapy. Until now, there are more than 17 kinds of nanomedicine for cancer therapy approved globally. Thereinto, conjugated nanomedicine, as an important type of nanomedicine, can not only possess the targeted delivery of chemotherapeutics with great precision but also achieve controlled drug release to avoid adverse effects. Meanwhile, conjugated nanomedicine provides the platform for combining several different therapeutic approaches (chemotherapy, photothermal therapy, photodynamic therapy, thermodynamic therapy, immunotherapy, etc.) with the purpose of achieving synergistic effects during cancer treatment. Therefore, this review focuses on conjugated nanomedicine and its various applications in synergistic chemotherapy. Additionally, the further perspectives and challenges of the conjugated nanomedicine are also addressed, which clarifies the design direction of a new generation of conjugated nanomedicine and facilitates the translation of them from the bench to the bedside.

Stimulus-responsive self-assembled prodrugs in cancer therapy

Small-molecule prodrugs have become the main toolbox to improve the unfavorable physicochemical properties of potential therapeutic compounds in contemporary anti-cancer drug development. Many approved small-molecule prodrugs, however, still face key challenges in their pharmacokinetic (PK) and pharmacodynamic (PD) properties, thus severely restricting their further clinical applications. Self-assembled prodrugs thus emerged as they could take advantage of key benefits in both prodrug design and nanomedicine, so as to maximize drug loading, reduce premature leakage, and improve PK/PD parameters and targeting ability. Notably, temporally and spatially controlled release of drugs at cancerous sites could be achieved by encoding various activable linkers that are sensitive to chemical or biological stimuli in the tumor microenvironment (TME). In this review, we have comprehensively summarized the recent progress made in the development of single/multiple-stimulus-responsive self-assembled prodrugs for mono- and combinatorial therapy. A special focus was placed on various prodrug conjugation strategies (polymer-drug conjugates, drug-drug conjugates, etc.) that facilitated the engineering of self-assembled prodrugs, and various linker chemistries that enabled selective controlled release of active drugs at tumor sites. Furthermore, some polymeric nano-prodrugs that entered clinical trials have also been elaborated here. Finally, we have discussed the bottlenecks in the field of prodrug nanoassembly and offered potential solutions to overcome them. We believe that this review will provide a comprehensive reference for the rational design of effective prodrug nanoassemblies that have clinic translation potential.

Regulation of drug release performance using mixed doxorubicin-doxorubicin dimer nanoparticles as a pH-triggered drug self-delivery system

A mixed drug self-delivery system (DSDS) with high drug content (>50%) was developed to regulate pH-triggered drug release, based on two doxorubicin (DOX)-DOX dimmers: D-DOXADH and D-DOXcar conjugated with acid-labile dynamic covalent bonds (hydrazone and carbamate, respectively) and stabilized with PEGylated D-DOXADH (D-DOXADH-PEG). Owing to the different stability of the dynamic covalent bonds in the two dimers and the noncovalent interaction between them, pH-triggered drug release could be easily regulated by adjusting the feeding ratios of the two DOX-DOX dimers in the mixed DSDS. Similar in vitro cellular toxicity was achieved with the mixed DSDS nanoparticles prepared with different feeding ratios. The mixed DSDS nanoparticles had a similar DOX content and diameter but different drug releasing rates. The MTT assays revealed that a high anti-tumor efficacy could be achieved with the slow-release mixed DSDS nanoparticles.

One-pot synthesis and enzyme-responsiveness of amphiphilic doxorubicin prodrug nanomicelles for cancer therapeutics

In this study, we report a one-pot synthesis and enzyme-responsiveness of polyethylene glycol (PEG) and glutamic acid (Glu)-based amphiphilic doxorubicin (DOX) prodrug nanomicelles for cancer therapeutics. The nanomicelles were accomplished by esterification and amidation reactions. The nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) data confirmed the structure of nanomicelles. The DOX-loaded nanomicelles showed a DLS-measured average size of 107 nm and excellent stability in phosphate-buffered saline (PBS) for 7 days. The drug loading and cumulative release rates were measured by ultraviolet-visible (UV-vis) spectrophotometry at 481 nm. The cumulative release rate could reach 100% in an enzyme-rich environment. Further, the therapeutic efficiency of nanomicelles to cancer cells was determined by cell viability and cellular uptake and distribution using HeLa cells. The cell viability study showed that the DOX-loaded nanomicelles could effectively inhibit the HeLa cell proliferation. The cellular uptake study confirmed that the nanomicelles could be effectively ingested by HeLa cells and distributed into cell nuclei. Based on the collective experimental data, this study demonstrated that the synthesized nanomicellar prodrug of DOX is a potential candidate for cancer therapeutics.

A doxorubicin-based nanomedicine with a one-pot synthesis method and FDA-approved materials could solve the problems of a complicated preparation process and avoid the use of non-FDA-approved materials for clinical use and industrial production.

Acid-triggered degradable diblock poly(doxorubicin)-polyethylene glycol polyprodrug with doxorubicin as structural unit for tumor intracellular delivery

Polyprodrugs, in which drug was used as the structural unit by linking with each other via the dynamic covalent bonds in the main chain, are expected to endow excellent drug delivery performance. Here, acid-triggered degradable diblock polyprodrug, poly(doxorubicin)-polyethylene glycol (PDOX-PEG), was designed with DOX as structural unit alternately linked with acid-labile hydrazone and maleic amide groups, by the polycondensation of DOX-based dimers (D-DOX_ADH or D-DOX_MAH) with PEGylated dimer (DOX-ADH-DOX-PEG) as end capping agent. The optimized PDOX-PEG, which was synthesized with D-DOX_ADH and the PEGylated dimer at a feeding ratio of 10%, possessed a high M_n of 3.1 × 10⁴ g/mol with a high DOX content of 75.42%. It could easily self-assemble into near spherical nanoparticles with average hydrodynamic diameter of 135 nm. They showed excellent pH-triggered sustained drug release owing to the acid-triggered degradation of the polyprodrug block in the tumor intracellular microenvironment, with low premature drug leakage of 4.39 % within 60 h. The MTT results indicated the enhanced antitumor efficacy of the proposed PDOX-PEG nanoparticles than free DOX. The results demonstrated the promising potential of the proposed acid-triggered degradable diblock PDOX-PEG polyprodrug for tumor treatment.

Nanoencapsulated Doxorubicin Prevents Mucositis Development in Mice

Doxorubicin (DOX), a chemotherapy drug successfully used in the therapy of various types of cancer, is currently associated with the mucositis development, an inflammation that can cause ulcerative lesions in the mucosa of the gastrointestinal tract, abdominal pain and secondary infections. To increase the safety of the chemotherapy, we loaded DOX into nanostructured lipid carriers (NLCs). The NLC-DOX was characterized by HPLC, DLS, NTA, Zeta potential, FTIR, DSC, TEM and cryogenic-TEM. The ability of NLC-DOX to control the DOX release was evaluated through in vitro release studies. Moreover, the effect of NLC-DOX on intestinal mucosa was compared to a free DOX solution in C57BL/6 mice. The NLC-DOX showed spherical shape, high drug encapsulation efficiency (84.8 ± 4.6%), high drug loading (55.2 ± 3.4 mg/g) and low average diameter (66.0-78.8 nm). The DSC and FTIR analyses showed high interaction between the NLC components, resulting in controlled drug release. Treatment with NLC-DOX attenuated DOX-induced mucositis in mice, improving shortening on villus height and crypt depth, decreased inflammatory parameters, preserved intestinal permeability and increased expression of tight junctions (ZO-1 and Ocludin). These results indicated that encapsulation of DOX in NLCs is viable and reduces the drug toxicity to mucosal structures.

Carrier-free nanodrugs for safe and effective cancer treatment

Clinical applications of many anti-cancer drugs are restricted due to their hydrophobic nature, requiring use of harmful organic solvents for administration, and poor selectivity and pharmacokinetics resulting in off-target toxicity and inefficient therapies. A wide variety of carrier-based nanoparticles have been developed to tackle these issues, but such strategies often fail to encapsulate drug efficiently and require significant amounts of inorganic and/or organic nanocarriers which may cause toxicity problems in the long term. Preparation of nano-formulations for the delivery of water insoluble drugs without using carriers is thus desired, requiring elegantly designed strategies for products with high quality, stability and performance. These strategies include simple self-assembly or involving chemical modifications via coupling drugs together or conjugating them with various functional molecules such as lipids, carbohydrates and photosensitizers. During nanodrugs synthesis, insertion of redox-responsive linkers and tumor targeting ligands endows them with additional characteristics like on-target delivery, and conjugation with immunotherapeutic reagents enhances immune response alongside therapeutic efficacy. This review aims to summarize the methods of making carrier-free nanodrugs from hydrophobic drug molecules, evaluating their performance, and discussing the advantages, challenges, and future development of these strategies.