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

Polysaccharide nanoparticles for oral controlled drug delivery: the role of drug-polymer and interpolymer interactions

Introduction: The oral route still represents the most popular way of administering drugs; nowadays oral administration faces new challenges, in particular with regards to the delivery of APIs that are poorly absorbed and sensitive to degradation such as macromolecules and biotechnological drugs. Nanoparticles are promising tools for the efficient delivery of these drugs to the gastrointestinal tract. Areas covered:Approaches and techniques for the formulation of drugs, with particular focus on the preparation of polysaccharide nanoparticles obtained by non-covalent interactions. Expert opinion:Polysaccharide-based nanoparticulate systems offer the opportunity to address some of the issues posed by biotechnological drugs, as well as by small molecules, with problems of stability/intestinal absorption, by exploiting the capability of the polymer to establish non-covalent bonds with functional groups in the chemical structure of the API. This area of research will continue to grow, provided that these drug delivery technologies will efficaciously be translated into systems that can be manufactured on a large scale under GMP conditions. Industrial scale-up represents the biggest obstacle to overcome in view of the transformation of very promising results obtained on lab scale into medicinal products. To do that, an effort toward the simplification of the process and technologies is necessary.

Developments of Smart Drug-Delivery Systems Based on Magnetic Molecularly Imprinted Polymers for Targeted Cancer Therapy: A Short Review

Cancer therapy is still a huge challenge, as especially chemotherapy shows several drawbacks like low specificity to tumor cells, rapid elimination of drugs, high toxicity and lack of aqueous solubility. The combination of molecular imprinting technology with magnetic nanoparticles provides a new class of smart hybrids, i.e., magnetic molecularly imprinted polymers (MMIPs) to overcome limitations in current cancer therapy. The application of these complexes is gaining more interest in therapy, due to their favorable properties, namely, the ability to be guided and to generate slight hyperthermia with an appropriate external magnetic field, alongside the high selectivity and loading capacity of imprinted polymers toward a template molecule. In cancer therapy, using the MMIPs as smart-drug-delivery robots can be a promising alternative to conventional direct administered chemotherapy, aiming to enhance drug accumulation/penetration into the tumors while fewer side effects on the other organs. Overview: In this review, we state the necessity of further studies to translate the anticancer drug-delivery systems into clinical applications with high efficiency. This work relates to the latest state of MMIPs as smart-drug-delivery systems aiming to be used in chemotherapy. The application of computational modeling toward selecting the optimum imprinting interaction partners is stated. The preparation methods employed in these works are summarized and their attainment in drug-loading capacity, release behavior and cytotoxicity toward cancer cells in the manner of in vitro and in vivo studies are stated. As an essential issue toward the development of a body-friendly system, the biocompatibility and toxicity of the developed drug-delivery systems are discussed. We conclude with the promising perspectives in this emerging field. Areas covered: Last ten years of publications (till June 2020) in magnetic molecularly imprinted polymeric nanoparticles for application as smart-drug-delivery systems in chemotherapy.

Filgrastim loading in PLGA and SLN nanoparticulate system: a bioinformatics approach

OBJECTIVE

In this research work, we hypothesized to predict the nanoparticulate system, best suited for targeted delivery of filgrastim. Significance: Targeted delivery of filgrastim to bone marrow is required to decrease the incidence of neutropenia/febrile neutropenia. This is achieved by nanoparticulate systems, duly designed by bioinformatics approach.

METHOD

The targeted delivery of filgrastim in nanoparticulate system was achieved by molecular dynamics (MD) simulation studies. Two matrices comprising PLGA and SLN (tripalmitin, core component of SLN system) were modeled separately with proposed drug filgrastim. Energy minimization of all systems was done using the steepest descent method. PLGA and tripalmitin systems were equalized at 310 °C, at 1 bar pressure with Berendsen barostat for 200 ps using a v-rescale thermostat for 100 ps. Atomistic MD simulations of four model system and mass density of interacting systems were calculated.

RESULTS

The mass density maps of each nanoparticle system, that is, PLGA and tripalmitin showed an increase in density toward the end of the simulation. The contact numbers attained equilibria with the average number of approx.. 1500 contacts in case of tripalmitin-filgrastim system. While PLGA-filgrastim system shows lesser contacts as compared to tripalmitin with average contacts of approx. 1000.The binding free energy was predicted to be -1104 kJ/mol in tripalmitin-filgrastim complex and -421 kJ/mol in PLGA-filgrastim system.

CONCLUSION

Findings of study revealed that both nanoparticle systems assumed to be good model for drug-carrier systems. Though SLN systems were thought to be more appropriate than PLGA, still the in vivo findings could ascertain this hypothesis in futuristic work.

Advances in Nanoparticles as Anticancer Drug Delivery Vector: Need of this Century

Background:

Nanotechnology has contributed a great deal to the field of medical science. Smart drugdelivery vectors, combined with stimuli-based characteristics, are becoming increasingly important. The use of external and internal stimulating factors can have enormous benefits and increase the targeting efficiency of nanotechnology platforms. The pH values of tumor vascular tissues are acidic in nature, allowing the improved targeting of anticancer drug payloads using drug-delivery vectors. Nanopolymers are smart drug-delivery vectors that have recently been developed and recommended for use by scientists because of their potential targeting capabilities, non-toxicity and biocompatibility, and make them ideal nanocarriers for personalized drug delivery.

Method:

The present review article provides an overview of current advances in the use of nanoparticles (NPs) as anticancer drug-delivery vectors.

Results:

This article reviews the molecular basis for the use of NPs in medicine, including personalized medicine, personalized therapy, emerging vistas in anticancer therapy, nanopolymer targeting, passive and active targeting transports, pH-responsive drug carriers, biological barriers, computer-aided drug design, future challenges and perspectives, biodegradability and safety.

Conclusions:

This article will benefit academia, researchers, clinicians, and government authorities by providing a basis for further research advancements.

Pectin polymers for colon-targeted antitumor drug delivery

The use of chemotherapeutic drugs in the treatment of malignant tumors is always associated with the severe side effects negatively affecting all organs and systems in human body. One of the approaches for reduction of the toxic influence and enhancement of the antitumor drug administration efficiency is supposed to be the use of the biopolymer delivery systems. Pectins are considered the most promising components for colon targeted drug dosage forms as they are stable in the changing gastrointestinal media and easily degraded by pectinases produced by colonic microflora. A various range of the pectin-containing delivery systems were developed contributing higher concentration of the active drug molecules in particular site inside intestine and their lower blood level resulting in lowered risk of the severe side effects. This review discusses the various forms of the pectin-based materials such as hydrogels, tablets and pellets, films, microspheres, microsponges, nanoparticles, etc. as drug delivery device and attempted to report the vast literature available on pectin biopolymers in drug delivery applications.

The Design of Poly(lactide-co-glycolide) Nanocarriers for Medical Applications

Polymeric biomaterials have found widespread applications in nanomedicine, and poly(lactide-co-glycolide), (PLGA) in particular has been successfully implemented in numerous drug delivery formulations due to its synthetic malleability and biocompatibility. However, the need for preconception in these formulations is increasing, and this can be achieved by selection and elimination of design variables in order for these systems to be tailored for their specific applications. The starting materials and preparation methods have been shown to influence various parameters of PLGA-based nanocarriers and their implementation in drug delivery systems, while the implementation of computational simulations as a component of formulation studies can provide valuable information on their characteristics. This review provides a critical summary of the synthesis and applications of PLGA-based systems in bio-medicine and outlines experimental and computational design considerations of these systems.

Understanding nanoparticle flow with a new in vitro experimental and computational approach using hydrogel channels

Nanoparticles (NPs) are considered as one of the most promising drug delivery vehicles and a next-generation solution for current medical challenges. In this context, variables related to flow of NPs such as the quantity of NPs lost during transport and flow trajectory greatly affect the clinical efficiency of NP drug delivery systems. Currently, there is little knowledge of the physical mechanisms dominating NP flow inside the human body due to the limitations of available experimental tools for mimicking complex physiological environments at the preclinical stage. Here, we report a coupled experimental and computational fluid dynamics (CFD)-based novel in vitro approach to predict the flow velocity and binding of NP drug delivery systems during transport through vasculature. Poly(hydroxyethyl)methacrylate hydrogels were used to form soft cylindrical constructs mimicking vascular sections as flow channels for synthesized iron oxide NPs in these first-of-its-kind transport experiments. Brownian dynamics and material of the flow channels played key roles in NP flow, based on the measurements of NP flow velocity over seven different mass concentrations. A fully developed laminar flow of the NPs under these conditions was simultaneously predicted using CFD. Results from the mass loss of NPs during flow indicated a diffusion-dominated flow at higher particle concentrations but a flow controlled by the surrounding fluid and Brownian dynamics at the lowest NP concentrations. The CFD model predicted a mass loss of 1.341% and 6.253% for the 4.12 g·mL^-1 and 2.008 g·mL^-1 inlet mass concentrations of the NPs, in close confirmation with the experimental results. This further highlights the reliability of our new in vitro technique in providing mechanistic insights of NP flow for potential preclinical stage applications.

Strategic Approaches for Colon Targeted Drug Delivery: An Overview of Recent Advancements

Colon targeted drug delivery systems have gained a great deal of attention as potential carriers for the local treatment of colonic diseases with reduced systemic side effects and also for the enhanced oral delivery of various therapeutics vulnerable to acidic and enzymatic degradation in the upper gastrointestinal tract. In recent years, the global pharmaceutical market for biologics has grown, and increasing demand for a more patient-friendly drug administration system highlights the importance of colonic drug delivery as a noninvasive delivery approach for macromolecules. Colon-targeted drug delivery systems for macromolecules can provide therapeutic benefits including better patient compliance (because they are pain-free and can be self-administered) and lower costs. Therefore, to achieve more efficient colonic drug delivery for local or systemic drug effects, various strategies have been explored including pH-dependent systems, enzyme-triggered systems, receptor-mediated systems, and magnetically-driven systems. In this review, recent advancements in various approaches for designing colon targeted drug delivery systems and their pharmaceutical applications are covered with a particular emphasis on formulation technologies.

Nanoformulation-by-design: an experimental and molecular dynamics study for polymer coated drug nanoparticles

Experimental studies of drug–polymer nanoparticle formation combined with molecular dynamics simulations provide atomistic explanations for the high drug loadings obtained.

Single-Molecule Characterization of Drug Delivery Systems

Delivery of the drug to a desired point of body and controlled release of the therapeutic agent are important features, provided by drug delivery systems (DDSs), for development of today's effective medicines. A variety of nanomaterials or nanomolecules such as lipids/liposomes, nucleic acids, peptides/proteins, composites, polymers, or carbon nanotubes can be used as DDSs. Single-molecule characterization of these small materials in terms of their size, shape, surface, encapsulation efficiency, as well as interaction with the drug-receiving cell has importance for their efficiency. The loading, distribution, or leakage of the drug as well as its interaction with DDS should also be characterized. Although diverse techniques are present for characterization of specific DDS material, methods such as electron microscopy and fluorescence microscopy are widely used. In this review, the current methodologies utilized for the single-molecule characterization of mostly preferred DDS materials were presented.

Recent Advancements in Non-Invasive Formulations for Protein Drug Delivery

Advancements in biotechnology and protein engineering expand the availability of various therapeutic proteins including vaccines, antibodies, hormones, and growth factors. In addition, protein drugs hold many therapeutic advantages over small synthetic drugs in terms of high specificity and activity. This has led to further R&D investment in protein-based drug products and an increased number of drug approvals for therapeutic proteins. However, there are many biological and biopharmaceutical obstacles inherent to protein drugs including physicochemical and enzymatic destabilization, which limit their development and clinical application. Therefore, effective formulations of therapeutic proteins are needed to overcome the various physicochemical and biological barriers. In current medical practice, protein drugs are predominantly available in injectable formulations, which have disadvantages including pain, the possibility of infection, high cost, and low patient compliance. Consequently, non-invasive drug delivery systems for therapeutic proteins have gained great attention in the research and development of biomedicines. Therefore, this review covers the various formulation approaches to optimizing the delivery properties of protein drugs with an emphasis on improving bioavailability and patient compliance. It provides a comprehensive update on recent advancements in nanotechnologies with regard to non-invasive protein drug delivery systems, which is also categorized by the route of administrations including oral, nasal, transdermal, pulmonary, ocular, and rectal delivery systems.

Multivalency in a Dendritic Host-Guest System

Multivalency is an important instrument in the supramolecular chemistry toolkit for the creation of strong specific interactions. In this paper we investigate the multivalency effect in a dendritic host–guest system using molecular dynamics simulations. Specifically, we consider urea–adamantyl decorated poly(propyleneimine) dendrimers that together with compatible mono-, bi-, and tetravalent ureidoacetic acid guests can form dynamic patchy nanoparticles. First, we simulate the self-assembly of these particles into macromolecular nanostructures, showing guest-controlled reduction of dendrimer aggregation. Subsequently, we systematically study guest concentration dependent multivalent binding. At low guest concentrations multivalency of the guests clearly increases relative binding as tethered headgroups bind more often than free guests’ headgroups. We find that despite an abundance of binding sites, most of the tethered headgroups bind in close proximity, irrespective of the spacer length; nevertheless, longer spacers do increase binding. At high guest concentrations the dendrimer becomes saturated with bound headgroups, independent of guest valency. However, in direct competition the tetravalent guests prevail over the monovalent ones. This demonstrates the benefit of multivalency at high as well as low concentrations.

Investigating the Mechanism of L-Valine in Improving the Stability of Gabapentin Combining Chemical Analysis Experiments with Computational Pharmacy

The mechanism of L-Val on how to improve the stability of gabapentin (GBP) was described by the combination of chemical analysis experiments and computer simulations. Scanning electron microscope (SEM), powder X-ray diffraction (PXRD), and differential scanning calorimeter (DSC), coupled with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), were used to identify β-GBP prepared by rapid solvent removal method. The reaction barriers on crystal planes, β-GBP (100) and β-GBP (10-1), are smaller than α-GBP and γ-GBP, reaching 276.65 kJ/mol and 299.57 kJ/mol, respectively. Thus, it was easier for β-GBP to form lactam, and the occurrence of β-GBP would lead the worse stability of α-GBP. The addition of neutral amino acids such as L-Val could improve the stability of α-GBP effectively. The adsorption energy of α-GBP (002) crystal plane with L-Val is larger than that of other crystal planes, reaching 42.17 kJ/mol. Hydrogen bond was the combination of L-Val and GBP main crystal planes, which could inhibit the crystal transformation of α-GBP. These results suggest that neutral amino acid protectants, such as L-Val, could improve the stability of α-GBP effectively, and inhibition of crystal transformation is one of the effective methods to improve the stability of polymorphic drugs.

Curvature-driven adsorption of cationic nanoparticles to phase boundaries in multicomponent lipid bilayers

Understanding the interactions between surface-functionalized gold nanoparticles (NPs) and lipid bilayers is necessary to guide the design of NPs for biomedical applications. Recent experiments found that cationic NPs adsorb more strongly to phase-separated multicomponent lipid bilayers than single-component liquid-disordered bilayers, suggesting that phase separation affects NP-bilayer interactions. In this work, we use coarse-grained molecular dynamics simulations to investigate the effect of lipid phase behavior on the adsorption of small cationic NPs. We first determined the free energy change for adsorbing a NP to one-phase liquid-disordered and one-phase liquid-ordered bilayers. The simulations indicate that NP adsorption depends on a competition between favorable NP-lipid interactions and the unfavorable curvature deformation of the bilayer, resulting in stronger interactions with the liquid-disordered bilayer due to its lower bending modulus. We then measured the free energy change associated with moving a NP across the surface of a phase-separated bilayer and identified a free energy minimum at the phase boundary. The free energy minimum is attributed to the thickness gradient between the two phases that enables favorable NP-lipid interactions without necessitating large curvature deformations. The simulation results thus indicate that the intrinsic curvature present at phase boundaries drives preferential interactions with surface-adsorbed NPs, providing new insight into the forces that drive NP behavior at multicomponent, phase-separated lipid bilayers.

Pharmacokinetic analysis reveals limitations and opportunities for nanomedicine targeting of endothelial and extravascular compartments of tumours

Targeting of nanoparticles to tumours can potentially improve the specificity of imaging and treatments. We have developed a multicompartmental pharmacokinetic model in order to analyse some of the factors that control efficiency of targeting to intravascular (endothelium) and extravascular (tumour cells and stroma) compartments. We make the assumption that transport across tumour endothelium is an important step for subsequent nanoparticle accumulation in the tumour (area-under-the-curve, AUC) regardless of entry route (interendothelial and transendothelial routes) and study this through a multicompartmental simulation. Our model reveals that increasing endothelial targeting efficiency has a much stronger effect on the AUC than increasing extravascular targeting efficiency. Furthermore, our analysis reveals that both extravasation and intratumoral diffusion rates need to be increased in order to significantly increase the AUC of extravascular-targeted nanoparticles. Increasing the nanoparticle circulation half-life increases the AUC independently of extravasation and intratumoral diffusion. Targeting the extravascular compartment leads to a buildup in the first layer surrounding blood vessels at the expense of deeper layers (binding site barrier). This model explains some of the limitations of tumour targeting and provides important guidelines for the design of targeted nanomedicines.

Molecular Mechanism of Polycation-Induced Pore Formation in Biomembranes

Polycations are an attractive class of macromolecules with promising applications as drug/gene carriers and biocides. The chemical structure and concentration of a polycation determine its interaction with cellular membranes and, hence, are crucial parameters for designing efficient nontoxic polycations. However, the interaction of polycations with biomembranes at the molecular level and the corresponding free-energy landscape is not well understood. In this work, we investigate the molecular mechanism of interaction between a strong polycation substituted with alkyl moieties and zwitterionic membranes via long-time-scale all-atom molecular dynamics simulations and free-energy calculations combined with Langmuir monolayer, atomic force microscopy, and calcein-release experimental measurements. We found that the membrane activity of the polycation and its ability to induce pores in the membranes can be attributed to the polycation-induced changes in the bilayer organization, such as reduced membrane thickness, increased disorder of the acyl chains, reduced packing, and electrostatic field gradients between membrane leaflets. These changes facilitate the penetration of water into the membrane and the formation of aqueous defects/pores. The calculated free-energy profiles indicate that the polycation lowers the nucleation barrier for pore opening and the free energy for pore formation in a concentration-dependent manner. Above the critical coverage of the membrane, the polycation nucleates spontaneous pores in zwitterionic membranes. Our work demonstrates the potential of combining enhanced sampling methods in MD simulations with experiments for a quantitative description of various events in the polycation-membrane interaction cycle, such as strong adsorption on the membrane due to hydrophobic and electrostatic interactions, and pore formation.

Characterization of drug delivery vehicles using atomic force microscopy: current status

INTRODUCTION

The field of nanomedicine, utilizing nano-sized vehicles (nanoparticles and nanofibers) for targeted local drug delivery, has a promising future. This is dependent on the ability to analyze the chemical and physical properties of these drug carriers at the nanoscale and hence atomic force microscopy (AFM), a high-resolution imaging and local force-measurement technique, is ideally suited.

AREAS COVERED

Following a brief introduction to the technique, the review describes how AFM has been used in selected publications from 2015 to 2018 to characterize nanoparticles and nanofibers as drug delivery vehicles. These sections are ordered into areas of increasing AFM complexity: imaging/particle sizing, surface roughness/quantitative analysis of images, and analysis of force curves (to extract nanoindentation and adhesion data).

EXPERT OPINION

AFM imaging/sizing is used extensively for the characterization of nanoparticle and nanofiber drug delivery vehicles, with surface roughness and nanomechanical/adhesion data acquisition being less common. The field is progressing into combining AFM with other techniques, notably SEM, ToF-SIMS, Raman, Confocal, and UV. Current limitations include a 50 nm resolution limit of nanoparticles imaged within live cells and AFM tip-induced activation of cytoskeleton proteins. Following drug release real-time with AFM-spectroscopic techniques and studying drug interactions on cell receptors appear to be on the horizon.

Biomedical Applications of Silver Nanoparticles: An Up-to-Date Overview

During the past few years, silver nanoparticles (AgNPs) became one of the most investigated and explored nanotechnology-derived nanostructures, given the fact that nanosilver-based materials proved to have interesting, challenging, and promising characteristics suitable for various biomedical applications. Among modern biomedical potential of AgNPs, tremendous interest is oriented toward the therapeutically enhanced personalized healthcare practice. AgNPs proved to have genuine features and impressive potential for the development of novel antimicrobial agents, drug-delivery formulations, detection and diagnosis platforms, biomaterial and medical device coatings, tissue restoration and regeneration materials, complex healthcare condition strategies, and performance-enhanced therapeutic alternatives. Given the impressive biomedical-related potential applications of AgNPs, impressive efforts were undertaken on understanding the intricate mechanisms of their biological interactions and possible toxic effects. Within this review, we focused on the latest data regarding the biomedical use of AgNP-based nanostructures, including aspects related to their potential toxicity, unique physiochemical properties, and biofunctional behaviors, discussing herein the intrinsic anti-inflammatory, antibacterial, antiviral, and antifungal activities of silver-based nanostructures.

Hydrogel-Based Drug Delivery Nanosystems for the Treatment of Brain Tumors

Chemotherapy is commonly associated with limited effectiveness and unwanted side effects in normal cells and tissues, due to the lack of specificity of therapeutic agents to cancer cells when systemically administered. In brain tumors, the existence of both physiological barriers that protect tumor cells and complex resistance mechanisms to anticancer drugs are additional obstacles that hamper a successful course of chemotherapy, thus resulting in high treatment failure rates. Several potential surrogate therapies have been developed so far. In this context, hydrogel-based systems incorporating nanostructured drug delivery systems (DDS) and hydrogel nanoparticles, also denoted nanogels, have arisen as a more effective and safer strategy than conventional chemotherapeutic regimens. The former, as a local delivery approach, have the ability to confine the release of anticancer drugs near tumor cells over a long period of time, without compromising healthy cells and tissues. Yet, the latter may be systemically administered and provide both loading and targeting properties in their own framework, thus identifying and efficiently killing tumor cells. Overall, this review focuses on the application of hydrogel matrices containing nanostructured DDS and hydrogel nanoparticles as potential and promising strategies for the treatment and diagnosis of glioblastoma and other types of brain cancer. Some aspects pertaining to computational studies are finally addressed.

Molecular Insight into Drug-Loading Capacity of PEG-PLGA Nanoparticles for Itraconazole

Nanoparticles made of amphiphilic block copolymers comprising biodegradable core-forming blocks are very attractive for the preparation of drug-delivery systems with sustained release. Their therapeutic applications are, however, hindered by low values of the drug-loading content (DLC). The compatibility between the drug and the core-forming block of the copolymer is considered the most important factor affecting the DLC value. However, the molecular picture of the hydrophobic drug-copolymer interaction is still not fully recognized. Herein, we examined this complex issue using a range of experimental techniques in combination with atomistic molecular dynamics simulations. We performed an analysis of the interaction between itraconazole, a model hydrophobic drug, and a poly(ethylene glycol)-poly(lactide- co-glycolide) (PEG-PLGA) copolymer, a biodegradable copolymer commonly used for the preparation of drug-delivery systems. Our results clearly show that the limited capacity of the PEG-PLGA nanoparticles for the accumulation of hydrophobic drugs is due to the fact that the drug molecules are located only at the water-polymer interface, whereas the interior of the PLGA core remains empty. These findings can be useful in the rational design and development of amphiphilic copolymer-based drug-delivery systems.

Armamentarium of nanoscaled lipid drug delivery systems customized for oral administration: In silico docking patronage, absorption phenomenon, preclinical status, clinical status and future prospects

Poor drug solubility and bioavailability remain a significant and frequently encountered concern for pharmaceutical scientists. Nanoscaled lipid drug delivery systems (NSLDDS) have exhibited great potentials in oral delivery of poorly water-soluble drugs, primarily for lipophilic drugs, with several successful clinical products. In the past few years, we have find out that optimized composition of drug in lipid, surfactant, or mixture of lipid and surfactant omits the solubility, permeability and bioavailability issues, which are potential limitations for oral absorption of poorly water-soluble drugs. Lipids not only vary in structures and physiochemical properties, but also in their digestibility and absorption pathway; therefore selection of lipid excipients and dosage form has a pronounced effect on biopharmaceutical aspects of drug absorption and distribution both in vitro and in vivo. Therefore, in current critical review, a comprehensive overview of the different lipid based nanostructured drug delivery systems intended for oral administration has been presented. In addition, implication of in silico docking in designing of NSLDDS as well as mechanism of absorption of different lipid based nanoformulations through intestinal absorption window has also been offered. Moreover, attention has also been paid to NSLDDS that are currently undergoing preclinical or clinical analysis.

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.

The role of hydrophobic modification on hyaluronic acid dynamics and self-assembly

The advent of nanomedicine has rejuvenated the need for increased understanding of the fundamental physicochemical properties of polymeric amphiphiles. Hyaluronic acid (HA) is a hydrophilic polysaccharide that is frequently conjugated to hydrophobic moieties and then used to entrap dyes and therapeutics. Here, we develop computational models to examine the effects of the hydrophobic modification on supramolecular behavior among three systematically designed HA derivatives substituted with alkyl chains of increasing length. Our simulations coalesce with experimentally obtained results to demonstrate the dependence of supramolecular behavior on intramolecular forces. We show that the formation of clearly defined hydrophobic domains in samples of octadecylamine-modified HA compared to HA conjugates with shorter alkyl chains is a result of more favorable hydrophobic interactions. Trends in hydrodynamic radius and polydispersity are observed in experimental results that coalesce with theoretical calculations, suggesting that supramolecular properties are dependent on the physicochemical characteristics of individual polymer strands.

Modulating interactions between ligand-coated nanoparticles and phase-separated lipid bilayers by varying the ligand density and the surface charge

The interactions between nanoparticles and lipid bilayers are critical in applications of nanoparticles in nanomedicine, cell imaging, toxicology, and elsewhere. Here, we investigate the interactions between nanoparticles coated with neutral and/or charged ligands and phase-separated lipid bilayers using coarse-grained molecular dynamics simulation. Both penetration and adsorption processes as well as the final distribution of the nanoparticles can be readily modulated by varying the ligand density and the surface charge of the nanoparticles. Completely hydrophobic (neutral) nanoparticles with larger size initially preferentially penetrate into the liquid-disordered region of the lipid bilayer and finally transfer into the liquid-ordered region; partially hydrophilic nanoparticles with low or moderate surface charge tend to either distribute in the liquid-disordered region or be adsorbed on the surface of the lipid bilayer, while strongly hydrophilic nanoparticles with high surface charge always reside on the surface of the lipid bilayer. Interactions of the nanoparticles with the lipid bilayers are affected by the surface charge of nanoparticles, hydrophobic mismatch, bending of the ligands, and the packing state of the lipids. Insight in these factors can be used to improve the efficiency of designing nanoparticles for specific applications.

Polypeptide self-assemblies: nanostructures and bioapplications

Polypeptide copolymers can self-assemble into diverse aggregates. The morphology and structure of aggregates can be varied by changing molecular architectures, self-assembling conditions, and introducing secondary components such as polymers and nanoparticles. Polypeptide self-assemblies have gained significant attention because of their potential applications as delivery vehicles for therapeutic payloads and as additives in the biomimetic mineralization of inorganics. This review article provides an overview of recent advances in nanostructures and bioapplications related to polypeptide self-assemblies. We highlight recent contributions to developing strategies for the construction of polypeptide assemblies with increasing complexity and novel functionality that are suitable for bioapplications. The relationship between the structure and properties of the polypeptide aggregates is emphasized. Finally, we briefly outline our perspectives and discuss the challenges in the field.

Multiple consecutive recapture of rigid nanoparticles using a solid-state nanopore sensor

Solid-state nanopore sensors have been used to measure the size of a nanoparticle by applying a resistive pulse sensing technique. Previously, the size distribution of the population pool could be investigated utilizing data from a single translocation, however, the accuracy of the distribution is limited due to the lack of repeated data. In this study, we characterized polystyrene nanobeads utilizing single particle recapture techniques, which provide a better statistical estimate of the size distribution than that of single sampling techniques. The pulses and translocation times of two different sized nanobeads (80 nm and 125 nm in diameter) were acquired repeatedly as nanobeads were recaptured multiple times using an automated system controlled by custom-built scripts. The drift-diffusion equation was solved to find good estimates for the configuration parameters of the recapture system. The results of the experiment indicated enhancement of measurement precision and accuracy as nanobeads were recaptured multiple times. Reciprocity of the recapture and capacitive effects in solid state nanopores are discussed. Our findings suggest that solid-state nanopores and an automated recapture system can also be applied to soft nanoparticles, such as liposomes, exosomes, or viruses, to analyze their mechanical properties in single-particle resolution.

Curcumin or bisdemethoxycurcumin for nose-to-brain treatment of Alzheimer disease? A bio/chemo-informatics case study

The current study introduces a new idea of utilising several bio/chemoinformatics tools in comparing two bio-similar natural molecules viz. curcumin and bisdemethoxycurcumin (BDMC) in order to select a potential nose-to-brain remedy for Alzheimer disease. The comparison comprised several bio/chemo informatics tools. It encompassed all levels starting from loading the drug in a certain carrier; PLGA nanoparticles, to the biopharmaceutical level investigating the interaction with mucin and inhibition of P-gp blood-brain barrier efflux pumps. Finally, the therapeutic level was investigated by studying the interaction with pharmacological targets such as amyloid peptide plaques and cyclooxygenase2 enzyme responsible for the inflammatory reactions of the studied disease. The comparison revealed the superiority of curcumin over BDMC. Five new analogues were also hypothesised where diethoxybisdemethoxycurcumin was  recommended as a superior molecule. This work introduced the virtual utilisation of bio/chemo informatics tools as a reliable and economic alternative to the exhausting and resources-consuming wet-lab experimentation.

Effect of Polycation Structure on Interaction with Lipid Membranes

Interaction of polycations with lipid membranes is a very important issue in many biological and medical applications such as gene delivery or antibacterial usage. In this work, we address the influence of hydrophobic substitution of strong polycations containing quaternary ammonium groups on the polymer-zwitterionic membrane interactions. In particular, we focus on the polymer tendency to adsorb on or/and incorporate into the membrane. We used complementary experimental and computational methods to enhance our understanding of the mechanism of the polycation-membrane interactions. Polycation adsorption on liposomes was assessed using dynamic light scattering (DLS) and zeta potential measurements. The ability of the polymers to form hydrophilic pores in the membrane was evaluated using a calcein-release method. The polymer-membrane interaction at the molecular scale was explored by performing atomistic molecular dynamics (MD) simulations. Our results show that the length of the alkyl side groups plays an essential role in the polycation adhesion on the zwitterionic surface, while the degree of substitution affects the polycation ability to incorporate into the membrane. Both the experimental and computational results show that the membrane permeability can be dramatically affected by the amount of alkyl side groups attached to the polycation main chain.

Molecular dynamics study on the mechanism of polynucleotide encapsulation by chitosan

The safe and effective delivery of therapeutic genes into target cell interiors is of great importance in gene therapy. Chitosan has been extensively studied as a gene delivery carrier due to its good biocompatibility and biodegradability. Understanding the atomic interaction mechanism between chitosan and DNA is important in the design and application of chitosan-based drug and gene delivery systems. In this work, the interactions between single-stranded polynucleotides and different types of chitosan were systematically investigated by using molecular dynamics (MD) simulation. Our results demonstrate that the functional groups of chitosan, the types of base and length of polynucleotides regulate the interaction behavior between chitosan and polynucleotides. The encapsulation capacity of polynucleotide by chitosan is mainly balanced by two factors: the strength of polynucleotide binding to chitosan and the tendency of self-aggregation of polynucleotide in the solution. For -NH3+ chitosan, due to the strong electrostatic interaction, especially the H-bond between -NH3+ groups in chitosan and phosphate groups in polynucleotide, the aggregation effect could be partially eliminated. The good dispersal capacity of polynucleotides may improve the encapsulation of polynucleotides by chitosan, and hence increase the delivery and transfection efficiency of chitosan-based gene carrier.

A numerical model for aggregations formation and magnetic driving of spherical particles based on OpenFOAM®

BACKGROUND AND OBJECTIVE

This work presents a numerical model for the formation of particle aggregations under the influence of a permanent constant magnetic field and their driving process under a gradient magnetic field, suitably created by a Magnetic Resonance Imaging (MRI) device.

METHODS

The model is developed in the OpenFOAM platform and it is successfully compared to the existing experimental and numerical results in terms of aggregates size and their motion in water solutions. Furthermore, several series of simulations are performed for two common types of particles of different diameter in order to verify their aggregation and flow behaviour, under various constant and gradient magnetic fields in the usual MRI working range. Moreover, the numerical model is used to measure the mean length of aggregations, the total time needed to form and their mean velocity under different permanent and gradient magnetic fields.

RESULTS

The present model is found to predict successfully the size, velocity and distribution of aggregates. In addition, our simulations showed that the mean length of aggregations is proportional to the permanent magnetic field magnitude and particle diameter according to the relation : l¯_a=7.5B₀d_i^3/2. The mean velocity of the aggregations is proportional to the magnetic gradient, according to : u¯_a=6.63G˜B₀ and seems to reach a steady condition after a certain period of time. The mean time needed for particles to aggregate is proportional to permanent magnetic field magnitude, scaled by the relationship : t¯_a∝7B₀.

CONCLUSIONS

A numerical model to predict the motion of magnetic particles for medical application is developed. This model is found suitable to predict the formation of aggregations and their motion under the influence of permanent and gradient magnetic fields, respectively, that are produced by an MRI device. The magnitude of the external constant magnetic field is the most important parameter for the aggregations formation and their driving.

Selecting optimum protein nano-carriers for natural polyphenols using chemoinformatics tools

BACKGROUND

The normal fate of any natural product with a therapeutic potential is to be formulated into an effective medicine. However, the conventional methods of selecting the suitable formulations or carriers based on the formulator experiences, trials and errors as well as materials availability do not usually yield the optimal results.

HYPOTHESIS

We hypothesize the possibility of the virtual optimum selection of a protein carrier for two polyphenolic compounds widely investigated for their chemopreventive effects; resveratrol and curcumin using a combination of some chemoinformatics tools.

METHODS

Two protein-based nanoparticles namely; albumin and gelatin nanoparticles were compared as carriers for the two selected phytochemicals; resveratrol and curcumin. Resveratrol-albumin, resveratrol-gelatin and curcumin-albumin results were gathered from the literature. While, a new combination (formulation), comprising curcumin as the cargo and gelatin nanoparticles as the carrier, was prepared and evaluated as a potential medicine for breast cancer. Combined chemoinformatics tools, namely; molecular dynamics and molecular docking were used to determine the optimum carrier for each of the two chemopreventive agents.

RESULTS

A new curcumin-gelatin nanoparticulate formulation was prepared and proven cytotoxic after an application period of 48h on MCF-7 breast cancer cell-lines scoring an IC₅₀ value of 64.8µg/ml. The utilized chemoinformatics tools comprising the molecular dynamics simulations of the protein nano-particulate drug-carriers followed by the molecular docking of phytochemical drugs on these carriers could capture the optimum protein carrier for each of the tested phytochemical and hence propose a successful formulation.

CONCLUSION

This study presents one in a series that proves the novel addressed concept of the utilization of computational tools rather than wet-lab experimentation in providing better selection of drug-carrier pairs aiming for better formulations and the subsequent successful therapeutic effects.