Drug self-delivery systems: A comprehensive review on small molecule nanodrugs

Drug self-delivery systems are nanostructures composed of a drug as the main structural unit, having the ability of intracellular trafficking with no additional carrier. In these systems, the drug itself undertakes the functional and structural roles; thereby, the ancillary role of excipients and carrier-related limitations are circumvented and therapeutic effect is achieved at a much lower dose. Such advantages -which are mainly but not exclusively beneficial in cancer treatment- have recently led to an upsurge of research on these systems. Subsequently, various terminologies were utilized to describe them, referring to the same concept with different words. However, not all the systems developed based on the self-delivery approach are introduced using one of these keywords. Using a scoping strategy, this review aims to encompass the systems that have been developed as yet -inspired by the concept of self-delivery- and classify them in a coherent taxonomy. Two main groups are introduced based on the type of building blocks: small molecule-based nanomedicines and self-assembling hybrid prodrugs. Due to the diversity, covering the whole gamut of topics is beyond the scope of a single article, and, inevitably, the latter is just briefly introduced here, whereas the features of the former group are meticulously presented. Depending on whether the drug is merely a carrier for itself or carries a second drug as cargo, two classes of small molecule-based nanomedicines are defined (i.e., pure nanodrugs and carrier-mimicking systems, respectively), each having sub-branches. After introducing each branch and giving some examples, possible strategies for designing each particular system are visually displayed. The resultant mind map can create a macro view of the taken path and its prospects, give a profound insight into opportunities, spark new ideas, and facilitate overcoming obstacles. Taken together, one can foresee a brilliant future for self-delivery systems as a pioneering candidate for the next generation of drug delivery systems.

Fine-tuning the sequential drug release of nano-formulated mutual prodrugs dictates the combination effects

Nanoformulated mutual prodrugs able to release two drugs either in order or simultaneously which significantly affected the combination effects consistently in vitro and in vivo, and links the in vitro–in vivo optimization of therapeutic effects.

Guanidine–Curcumin Complex-Loaded Amine-Functionalised Hollow Mesoporous Silica Nanoparticles for Breast Cancer Therapy

The current study focuses on developing a tumour-targeted functionalised nanocarrier that wraps hollow mesoporous silica nanoparticles. The guanidine carbonate and curcumin are immobilised on the surface of 3-aminopropyl-triethoxy silane (APTES)-decorated hollow mesoporous silica nanoparticles (HMSNP), as confirmed through XPS and NMR analysis. XPS analysis demonstrates that the shape of the hysteresis loops is modified and that pore volume and pore diameter are consequently decreased compared to control. Guanidine (85%) and guanidine–curcumin complex (90%) were successfully encapsulated in HMSNAP and showed a 90% effective and sustained release at pH 7.4 for up to 72 h. Acridine orange/ethidium bromide dual staining determined that GuC-HMNSAP induced more late apoptosis and necrosis at 48 and 72 h compared with Gu-HMNSAP-treated cells. Molecular investigation of guanidine-mediated apoptosis was analysed using western blotting. It was found that cleaved caspases, c-PARP, and GSK-3β (Ser9) had increased activity in MCF-7 cells. GuC-HMSNAP increased the activity of phosphorylation of oncogenic proteins such as Akt (Ser473), c-Raf (Ser249), PDK1 (Ser241), PTEN (Ser380), and GSK-3β (Ser9), thus inducing cell death in MCF-7 cells. Altogether, our findings confirm that GuC-HMNSAP induces cell death by precisely associating with tumour-suppressing proteins, which may lead to new therapeutic approaches for breast cancer therapy.

Biomedically Relevant Applications of Bolaamphiphiles and Bolaamphiphile-Containing Materials

Bolaamphiphiles (BAs) are structurally segmented molecules with rich assembly characteristics and diverse physical properties. Interest in BAs as standalone active agents or as constituents of more complex therapeutic formulations has increased substantially in recent years. The preorganized amphiphilicity of BAs allows for a range of biological activities including applications that rely on multivalency. This review summarizes BA-related research in biomedically relevant areas. In particular, we review BA-related literature in four areas: gene delivery, antimicrobial materials, hydrogels, and prodrugs. We also discuss several distinguishing characteristics of BAs that impact their utility as biomedically relevant compounds.

From poly(alkyl cyanoacrylate) to squalene as core material for the design of nanomedicines

This review article covers the most important steps of the pioneering work of Patrick Couvreur and tries to shed light on his outstanding career that has been a source of inspiration for many decades. His discovery of biodegradable poly(alkyl cyanoacrylate) (PACA) nanoparticles (NPs) has opened large perspectives in nanomedicine. Indeed, NPs made from various types of alkyl cyanoacrylate monomers have been used in different applications, such as the treatment of intracellular infections or the treatment of multidrug resistant hepatocarcinoma. This latest application led to the Phase III clinical trial of Livatag^®, a PACA nanoparticulate formulation of doxorubicin. Despite the success of PACA NPs, the development of a novel type of NP with higher drug loadings and lower burst release was tackled by the discovery of squalene-based nanomedicines where the drug is covalently linked to the lipid derivative and the resulting conjugate is self-assembled into NPs. This pioneering work was accompanied by a wide range of novel applications which mainly dealt with the management of unmet medical needs (e.g. pancreatic cancer, brain ischaemia and spinal cord injury).

Implication of linker length on cell cytotoxicity, pharmacokinetic and toxicity profile of gemcitabine-docetaxel combinatorial dual drug conjugate

The present study investigates effect of linkers [zero length (without linker), short length linker (glycine and lysine) and long length linker (PEG1000, PEG2000 and PEG3500)] on pharmacokinetics and toxicity of docetaxel (DTX) and gemcitabine (GEM) bio-conjugates. Conjugates were synthesized via carbodiimide chemistry and characterized by ¹H NMR and FTIR. Conjugation of DTX and GEM via linkers showed diverse physiochemical and plasma stability profile. Cellular uptake mechanism in MCF-7 and MDA-MB-231 cell lines revealed clathrin mediated internalization of bio-conjugates developed by using long length linkers, leading to higher cytotoxicity compared with free drug congeners. DTX-PEG3500-GEM and DTX-PEG2000-GEM demonstrated 4.21 and 3.81-fold higher AUC_(0-∞) of GEM in comparison with GEM alone. DTX-PEG2000-GEM and DTX-PEG3500-GEM exhibited reduced hepato-, nephro- and haemolytic toxicity as evident via histopathology, biochemical markers and SEM analysis of RBCs. Conclusively, PEG2000 and PEG3500 significantly improved pharmacokinetics without any sign of toxicity and hence can be explored further for the development of dual-drug conjugates for better therapeutic efficacy.

Dual controlled delivery of squalenoyl-gemcitabine and paclitaxel using thermo-responsive polymeric micelles for pancreatic cancer

A thermoresponsive block copolymer has been developed with the capability to co-carry two drug molecules and to augment their cytotoxic properties via direct cell membrane interaction with cancer cells.

Prodrug Strategies for Paclitaxel

Paclitaxel is an anti-tumor agent with remarkable anti-tumor activity and wide clinical uses. However, it is also faced with various challenges especially for its poor water solubility and low selectivity for the target. To overcome these disadvantages of paclitaxel, approaches using small molecule modifications and macromolecule modifications have been developed by many research groups from all over the world. In this review, we discuss the different strategies especially prodrug strategies that are currently used to make paclitaxel more effective.

Matrices for combined delivery of proteins and synthetic molecules

With the increasing advancement of synergistic, multimodal approaches to influence the treatment of infectious and non-infectious diseases, we witness the development of enabling techniques merging necessary complexity with leaner designs and effectiveness. Systems- and polypharmacology ask for multi-potent drug combinations with many targets to engage with the biological system. These demand drug delivery designs for one single drug, dual drug release systems and multiple release matrices in which the macromolecular structure allows for higher solubilization, protection and sequential or combined release profiles. As a result, nano- and micromaterials have been evolved from mono- to dual drug carriers but are also an essential part to establish multimodality in polymeric matrices. Surface dynamics of particles creating interfaces between polymer chains and hydrogels inspired the development not only of biomedical adhesives but also of injectable hydrogels in which the nanoscale material is both, adhesive and delivery tool. These complex delivery systems are segmented into two delivery subunits, a polymer matrix and nanocarrier, to allow for an even higher tolerance of the incorporated drugs without adding further synthetic demands to the nanocarrier alone. The opportunities in these quite novel approaches for the delivery of small and biological therapeutics are remarkable and selected examples for applications in cancer and bone treatments are discussed.

Prodrug-based nanoparticulate drug delivery strategies for cancer therapy

Despite the rapid developments in nanotechnology and biomaterials, the efficient delivery of chemotherapeutic agents is still challenging. Prodrug-based nanoassemblies have many advantages as a potent platform for anticancer drug delivery, such as improved drug availability, high drug loading efficiency, resistance to recrystallization upon encapsulation, and spatially and temporally controllable drug release. In this review, we discuss prodrug-based nanocarriers for cancer therapy, including nanosystems based on polymer-drug conjugates, self-assembling small molecular weight prodrugs and prodrug-encapsulated nanoparticles (NPs). In addition, we discuss new trends in the field of prodrug-based nanoassemblies that enhance the delivery efficiency of anticancer drugs, with special emphasis on smart stimuli-triggered drug release, hybrid nanoassemblies, and combination drug therapy.