Tunable supramolecular self-assemblies based on cyclodextrin polymer as a loading platform for water-soluble drugs

Drug loading capacity is a crucial character of nano-scaled drug carriers to achieve high quality pharmaceutical preparations. However, efficient encapsulation of water-soluble small molecular drugs still faces large obstacles in many cases. Herein, we designed a novel supramolecular delivery system constructed by poly(β-cyclodextrin) containing benzoic acid groups (PCD-PA) and adamantyl terminated poly(ethylene glycol) (PEG-AD) to provide multiple intermolecular interactions for competent loading of water-soluble small-molecular drugs. PCD-PA had multiple host molecules, and PEG-AD could be inserted via host-guest interaction in different proportion to adjust the composition of supramolecular carrier. Meanwhile, π-π stacking and electrostatic interaction furnished by benzoic acid groups served as binding force for drug entrapment, which led to considerable loading capacity for several water-soluble drugs. Among the drugs with different chemical structures, mitoxantrone hydrochloride and doxorubicin hydrochloride bearing anthraquinone rings and several protonable amino groups acquired the highest loading content as about 14 % in PCD-PA3/PEG-AD supramolecular self-assemblies. Further computational simulations investigated the mechanism of drug loading based on the interactions between the carrier materials and the payloads. In addition, the weakly acidic environment obviously accelerated the release of certain drugs. All in all, this self-assembled supramolecular nano-system displayed great potentials as a delivery platform for diverse water-soluble drugs.

In silico-guided discovery and in vitro validation of novel sugar-tethered lysinated carbon nanotubes for targeted drug delivery of doxorubicin

CONTEXT

Multiwalled carbon nanotubes (MWCNTs) functionalized with lysine via 1,3-dipolar cycloaddition and conjugated to galactose or mannose are potential nanocarriers that can effectively bind to the lectin receptor in MDA-MB-231 or MCF-7 breast cancer cells. In this work, a method based on molecular dynamics (MD) simulation was used to predict the interaction of these functionalized MWCNTs with doxorubicin and obtain structural evidence that allows a better understanding of the drug loading and release process. The MD simulations showed that while doxorubicin only interacted with pristine MWCNTs through π-π stacking interactions, functionalized MWCNTs were also able to establish hydrogen bonds, suggesting that the functionalized groups improve doxorubicin loading. Moreover, the elevated adsorption levels observed for functionalized nanotubes further support this enhancement in loading efficiency. MD simulations also shed light on the intratumoral pH-specific release of doxorubicin from functionalized MWCNTs, which is induced by protonation of the daunosamine moiety. The simulations show that this change in protonation leads to a lower absorption of doxorubicin to the MWCNTs. The MD studies were then experimentally validated, where functionalized MWCNTs showed improved dispersion in aqueous medium compared to pristine MWCNTs and, in agreement with the computational predictions, increased drug loading capacity. Doxorubicin-loaded functionalized MWCNTs demonstrated specific release of doxorubicin in tumor microenvironment (pH = 5.0) with negligible release in the physiological pH (pH = 7.4). Furthermore, doxorubicin-free MWNCT nanoformulations exhibited insignificant cytotoxicity. The experimental studies yielded nearly identical results to the MD studies, underlining the usefulness of the method. Our functionalized MWCNTs represent promising non-toxic nanoplatforms with enhanced aqueous dispersibility and the potential for conjugation with ligands for targeted delivery of anti-cancer drugs to breast cancer cells.

METHODS

The computational model of a pristine carbon nanotube was created with the buildCstruct 1.2 Python script. The lysinated functionalized groups were added with PyMOL and VMD. The carbon nanotubes and doxorubicin molecules were parameterized using the general AMBER force field, and RESP charges were determined using Gaussian 09. Molecular dynamics simulations were carried out with the AMBER 20 software package. Adsorption levels were calculated using the water-shell function of cpptraj. Cytotoxicity was evaluated via a MTT assay using MDA-MB-231 and MCF-7 breast cancer cells. Drug uptake of doxorubicin and doxorubicin-loaded MWCNTs was measured by fluorescence microscopy.

Conjugation of a smart polymer to doxorubicin through a pH-responsive bond for targeted drug delivery and improving drug loading on graphene oxide

Polymeric nanoparticles have emerged as efficient carriers for anticancer drug delivery because they can improve the solubility of hydrophobic drugs and also can increase the bio-distribution of drugs throughout the bloodstream. In this work, a computational study is performed on a set of new pH-sensitive polymer-drug compounds based on an intelligent polymer called poly(β-malic acid) (PMLA). The molecular dynamics (MD) simulation is used to explore the adsorption and dynamic properties of PMLA-doxorubicin (PMLA-DOX) interaction with the graphene oxide (GOX) surface in acidic and neutral environments. The PMLA is bonded to DOX through an amide bond (PMLA-ami-DOX) and a hydrazone bond (PMLA-hz-DOX) and their adsorption behavior is compared with free DOX. Our results confirm that the polymer-drug prodrug shows unique properties. Analysis of the adsorption behavior reveals that this process is spontaneous and the most stable complex with a binding energy of -1210.262 kJ mol-1 is the GOX/PMLA-hz-DOX complex at normal pH. On the other hand, this system has a great sensitivity to pH so that in an acidic environment, its interaction with GOX became weaker while such behavior is not observed for the PMLA-ami-DOX complex. The results obtained from this study provide accurate information about the interaction of the polymer-drug compounds and nanocarriers at the atomic level, which can be useful in the design of smart drug delivery systems.

Antibacterial Activity of N,O-Acylated Chitosan Derivative

The antibacterial activity of N,O-acylated chitosan derivative with linoleic acid (CH_LA) was tested by disc and well diffusion, agar impregnation and microdilution methods against Staphylococcus aureus, Escherichia coli and Helicobacter pylori strains. Hydrophobically modified chitosan (HMC) was expected to exhibit enhanced antibacterial activity and specific mucin interactions. Although diffusion tests have not indicated the antibacterial potential of chitosan (CH) or CH_LA, the results of the microdilution method demonstrated that tested polymers significantly reduced the amount of living bacteria cells in different concentrations depending on the microorganism. Additionally, CH_LA was characterized by enhanced antibacterial activity compared to CH, which may suggest a different mechanism of interaction with S. aureus and H. pylori. Furthermore, the UV-VIS analysis revealed that the amphiphilic character of derivative led to strong CH_LA–mucin interactions. The study proved the high potential of CH_LA in antibacterial applications, especially for the gastrointestinal tract.

Mechanistic Understanding From Molecular Dynamics Simulation in Pharmaceutical Research 1: Drug Delivery

In this review, we outline the growing role that molecular dynamics simulation is able to play as a design tool in drug delivery. We cover both the pharmaceutical and computational backgrounds, in a pedagogical fashion, as this review is designed to be equally accessible to pharmaceutical researchers interested in what this new computational tool is capable of and experts in molecular modeling who wish to pursue pharmaceutical applications as a context for their research. The field has become too broad for us to concisely describe all work that has been carried out; many comprehensive reviews on subtopics of this area are cited. We discuss the insight molecular dynamics modeling has provided in dissolution and solubility, however, the majority of the discussion is focused on nanomedicine: the development of nanoscale drug delivery vehicles. Here we focus on three areas where molecular dynamics modeling has had a particularly strong impact: (1) behavior in the bloodstream and protective polymer corona, (2) Drug loading and controlled release, and (3) Nanoparticle interaction with both model and biological membranes. We conclude with some thoughts on the role that molecular dynamics simulation can grow to play in the development of new drug delivery systems.

Molecular engineering of the last-generation CNTs in smart cancer therapy by grafting PEG-PLGA-riboflavin

In this work, the effect of environment and additives on the self-assembly and delivery of doxorubicin (DOX) have been studied. A microfluidic system with better control over molecular interactions and high surface to volume ratio has superior performance in comparison to the bulk system. Moreover, carbon nanotube (CNT) and CNT-doped structures have a high surface area to incorporate the DOX molecules into a polymer and the presence of functional groups can influence the polymer-drug interactions. In this work, the interactions of DOX with both the polymeric complex and the nanotube structure have been investigated. For quantification of the interactions, H-bonding, gyration radius, root-mean-square deviation (RMSD), Gibbs free energy, radial distribution function (RDF), energy, and Solvent Accessible Surface Area (SASA) analyses have been performed. The most stable micelle-DOX interaction is attributed to the presence of BCN in the microfluidic system according to the gyration radius and RMSD. Meanwhile, for DOX-doped CNT interaction the phosphorus-doped CNT in the microfluidic system is more stable. The highest electrostatic interaction can be seen between polymeric micelles and DOX in the presence of BCN. For nanotube-drug interaction, phosphorus-doped carbon nanotubes in the microfluidic system have the largest electrostatic interaction with the DOX. RDF results show that in the microfluidic system, nanotube-DOX affinity is larger than that of nanotube-micelle.

pH-sensitive loading/releasing of doxorubicin using single-walled carbon nanotube and multi-walled carbon nanotube: A molecular dynamics study

BACKGROUND AND OBJECTIVE

Doxorubicin is one of the drugs used to treat cancer, and many studies have been conducted to control its release. In this study, carbon nanotubes have been proposed as a doxorubicin carrier, and the effect of carboxyl functional group on the controlled release of doxorubicin has been studied.

METHODS

This study has been done by molecular dynamics simulation and was based on changing the pH as a mechanism controller.

RESULTS

This work is intended to test the efficacy of this drug carrier for the release of doxorubicin. A comparison was also made between single-walled and double-walled carbon nanotubes to answer the question of which one can be a better carrier for doxorubicin. The study of DOXORUBICIN adsorption and release showed that the DOXORUBICIN adsorption on single-walled carbon nanotube and multi-walled carbon nanotube in neutral pH was stronger than it was in acidic pH, which could be due to the electrostatic interactions between the carboxyl group of nanotubes and DOXORUBICIN. Based on this and according to the investigation of hydrogen bonds, diffusion coefficients, and other results it was clear that the drug release in acidic pH was appropriate for body conditions. Since cancer tissues pH is acidic, this shows the suitability of carbon nanotube in drug delivery and DOXORUBICIN release in cancer tissues. In addition, it was shown that the blood pH (pH = 7) is suitable for DOXORUBICIN loading on the carbon nanotube and carbon nanotube-DOXORUBICIN linkage remained stable at this pH; accordingly, the carbon nanotube could deliver DOXORUBICIN in blood quite well and release it in cancerous tissues. This suggests the carbon nanotubes as a promising drug carrier in the cancer therapy which can be also investigated in experiments.

CONCLUSION

It was revealed that the bonds between multi-walled carbon nanotube and DOXORUBICIN was stronger and this complex had a slower release in the cancer tissues compared to the single-walled carbon nanotube; this can be regarded as an advantage over the single-walled carbon nanotube in the DOXORUBICIN delivery and release.

Boron nitride nanotubes as containers for targeted drug delivery of doxorubicin

Using molecular dynamics simulations, the adsorption and diffusion of doxorubicin drug molecules in boron nitride nanotubes are investigated. The interaction between doxorubicin and the nanotube is governed by van der Waals attraction. We find strong adsorption of doxorubicin to the wall for narrow nanotubes (radius of 9 Å). For larger radii (12 and 15 Å), the adsorption energy decreases, while the diffusion coefficient of doxorubicin increases. It does, however, not reach the values of pure water, as adsorption events still hinder the doxorubicin mobility. It is concluded that nanotubes wider than around 4 nm diameter can serve as efficient drug containers for targeted drug delivery of doxorubicin in cancer chemotherapy.

Molecular dynamics simulation of Doxorubicin loading with N-isopropyl acrylamide carbon nanotube in a drug delivery system

BACKGROUND AND OBJECTIVE

Doxorubicin is one of the common drugs used for cancer therapy. Molecular dynamics were applied to investigate the loading of Doxorubicin with thermosensitive N-isopropyl acrylamide Carbon nanotube carrier.

METHODS

The results showed that the smaller polymer chain length has more decrease of gyration radius. A decrease of gyration radius resulted in more concentrated aggregation with stronger bonds. Therefore, the shorter the polymer chain lengths, the more stable polymer interaction and better Doxorubicin delivery. Smaller polymers also form more hydrogen bonds with the drug leading to stronger and more stable carriers.

RESULTS

A lower amount of wall shear stress was found near the inner wall of the artery, distal to the plaque region (stenosis), and in both percentages of stenosis the maximum wall shear stress will accrue in the middle of the stenosis; however it is much more in the higher rate of stenosis.

CONCLUSIONS

The results indicated that N-isopropyl acrylamide - Carbon nanotube is suitable for the delivery of Doxorubicin, and five mer N-isopropyl acrylamide is the optimum carrier for Doxorubicin loading.

Unraveling the Impact of High-Order Silk Structures on Molecular Drug Binding and Release Behaviors

Silk continues to amaze: over the past decade, new research threads have emerged that include the use of silk fibroin for advanced pharmaceutics, including its suitability for drug delivery. Despite this ongoing interest, the details of silk fibroin structures and their subsequent drug interactions at the molecular level remain elusive, primarily because of the difficulties encountered in modeling the silk fibroin molecule. Here, we generated an atomistic silk model containing amorphous and crystalline regions. We then exploited advanced well-tempered metadynamics simulations to generate molecular conformations that we subsequently exposed to classical molecular dynamics simulations to monitor both drug binding and release. Overall, this study demonstrated the importance of the silk fibroin primary sequence, electrostatic interactions, hydrogen bonding, and higher-order conformation in the processes of drug binding and release.

Computational modelling of drug delivery to solid tumour: Understanding the interplay between chemotherapeutics and biological system for optimised delivery systems

Drug delivery to solid tumour involves multiple physiological, biochemical and biophysical processes taking place across a wide range of length and time scales. The therapeutic efficacy of anticancer drugs is influenced by the complex interplays among the intrinsic properties of tumours, biophysical aspects of drug transport and cellular uptake. Mathematical and computational modelling allows for a well-controlled study on the individual and combined effects of a wide range of parameters on drug transport and therapeutic efficacy, which would not be possible or economically viable through experimental means. A wide spectrum of mathematical models has been developed for the simulation of drug transport and delivery in solid tumours, including PK/PD-based compartmental models, microscopic and macroscopic transport models, and molecular dynamics drug loading and release models. These models have been used as a tool to identify the limiting factors and for optimal design of efficient drug delivery systems. This article gives an overview of the currently available computational models for drug transport in solid tumours, together with their applications to novel drug delivery systems, such as nanoparticle-mediated drug delivery and convection-enhanced delivery.

Characterization of the interaction forces in a drug carrier complex of doxorubicin with a drug-binding peptide

Polypeptide-based materials are used as building blocks for drug delivery systems aimed at toxicity decrease in chemotherapeutics. A molecular-level approach is adopted for investigating the non-covalent interactions between doxorubicin and a recently synthesized drug-binging peptide as a key part of a system for delivery to neoplastic cells. Molecular dynamics simulations in aqueous solution at room and body temperature are applied to investigate the structure and the binding modes within the drug-peptide complex. The tryptophans are outlined as the main chemotherapeutic adsorption sites, and the importance of their placement in the peptide sequence is highlighted. The drug-peptide binging energy is evaluated by density functional theory calculations. Principal component analysis reveals comparable importance of several types of interaction for the binding strength. π-Stacking is dominant, but other factors are also significant: intercalation, peptide backbone stacking, electrostatics, dispersion, and solvation. Intra- and intermolecular H-bonding also stabilizes the complexes. The influence of solvent molecules on the binding energy is mild. The obtained data characterize the drug-to-peptide attachment as a mainly attractive collective process with interactions spanning a broad range of values. These results explain with atomistic detail the experimentally registered doxorubicin-binging ability of the peptide and outline the complex as a prospective carrying unit that can be employed in design of drug delivery systems.

Computational and experimental approaches for investigating nanoparticle-based drug delivery systems

Most therapeutic agents suffer from poor solubility, rapid clearance from the blood stream, a lack of targeting, and often poor translocation ability across cell membranes. Drug/gene delivery systems (DDSs) are capable of overcoming some of these barriers to enhance delivery of drugs to their right place of action, e.g. inside cancer cells. In this review, we focus on nanoparticles as DDSs. Complementary experimental and computational studies have enhanced our understanding of the mechanism of action of nanocarriers and their underlying interactions with drugs, biomembranes and other biological molecules. We review key biophysical aspects of DDSs and discuss how computer modeling can assist in rational design of DDSs with improved and optimized properties. We summarize commonly used experimental techniques for the study of DDSs. Then we review computational studies for several major categories of nanocarriers, including dendrimers and dendrons, polymer-, peptide-, nucleic acid-, lipid-, and carbon-based DDSs, and gold nanoparticles. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov.

Synthesis, self-assembly, and in vitro toxicity of fatty acids-modified Bletilla striata polysaccharide

Hydrophobic modification of Bletilla striata polysaccharide (BSP) was performed by grafting fatty acids to BSP backbone and then characterized on their physicochemical properties. All neutral derivatives were able to self-assemble into spherical particles within the size range of 250-400 nm, their size and critical micelle concentration decreased with increasing hydrophobicity and substitution degree of the fatty acids. Also, the BSP-stearic acid conjugates showed a preferable performance on hemolysis test and cytotoxicity analysis on HepG2 cells, which suggested their potential application as a drug delivery vector.

Molecular dynamics simulations of simple aromatic compounds adsorption on single-walled carbon nanotubes

We have conducted MD simulations and RDG calculations to reveal the mechanisms of simple aromatic compounds adsorption on SWCNTs.

Molecular simulation of pH-dependent diffusion, loading, and release of doxorubicin in graphene and graphene oxide drug delivery systems

We investigated the pH-dependent energetics and mechanisms of doxorubicin (DOX) drug adsorption on graphene oxide nanocarriers using molecular dynamics simulation.

Adsorption of doxorubicin on citrate-capped gold nanoparticles: insights into engineering potent chemotherapeutic delivery systems

Gold nanomaterials have received great interest for their use in cancer theranostic applications over the past two decades. Many gold nanoparticle-based drug delivery system designs rely on adsorbed ligands such as DNA or cleavable linkers to load therapeutic cargo. The heightened research interest was recently demonstrated in the simple design of nanoparticle-drug conjugates wherein drug molecules are directly adsorbed onto the as-synthesized nanoparticle surface. The potent chemotherapeutic, doxorubicin often serves as a model drug for gold nanoparticle-based delivery platforms; however, the specific interaction facilitating adsorption in this system remains understudied. Here, for the first time, we propose empirical and theoretical evidence suggestive of the main adsorption process where (1) hydrophobic forces drive doxorubicin towards the gold nanoparticle surface before (2) cation-π interactions and gold-carbonyl coordination between the drug molecule and the cations on AuNP surface facilitate DOX adsorption. In addition, biologically relevant compounds, such as serum albumin and glutathione, were shown to enhance desorption of loaded drug molecules from AuNP at physiologically relevant concentrations, providing insight into the drug release and in vivo stability of such drug conjugates.

Molecular weight dependence of structure and properties of chitosan oligomers

Molecular weight dependence of water solubility of COS.