Assessment of adsorption behavior of 5-fluorouracil and pyrazinamide on carbon nitride and folic acid-conjugated carbon nitride nanosheets for targeting drug delivery

Computer-aided nanodrug discovery: recent progress and future prospects

Nanodrugs, which utilise nanomaterials in disease prevention and therapy, have attracted considerable interest since their initial conceptualisation in the 1990s. Substantial efforts have been made to develop nanodrugs for overcoming the limitations of conventional drugs, such as low targeting efficacy, high dosage and toxicity, and potential drug resistance. Despite the significant progress that has been made in nanodrug discovery, the precise design or screening of nanomaterials with desired biomedical functions prior to experimentation remains a significant challenge. This is particularly the case with regard to personalised precision nanodrugs, which require the simultaneous optimisation of the structures, compositions, and surface functionalities of nanodrugs. The development of powerful computer clusters and algorithms has made it possible to overcome this challenge through in silico methods, which provide a comprehensive understanding of the medical functions of nanodrugs in relation to their physicochemical properties. In addition, machine learning techniques have been widely employed in nanodrug research, significantly accelerating the understanding of bio-nano interactions and the development of nanodrugs. This review will present a summary of the computational advances in nanodrug discovery, focusing on the understanding of how the key interfacial interactions, namely, surface adsorption, supramolecular recognition, surface catalysis, and chemical conversion, affect the therapeutic efficacy of nanodrugs. Furthermore, this review will discuss the challenges and opportunities in computer-aided nanodrug discovery, with particular emphasis on the integrated "computation + machine learning + experimentation" strategy that can potentially accelerate the discovery of precision nanodrugs.

A DFT study of sulforaphane adsorption on the group III nitrides (B12N12, Al12N12 and Ga12N12) nanocages

In this paper, the adsorption behavior of group III nitrides (B12N12, Al12N12, and Ga12N12) nanocages to sulforaphane (SF) anticancer medicine were studied by density functional theory (DFT). The adsorption energy, solvation energy, desorption time and related quantum molecular descriptors were calculated in neutral and acidic solutions. When the drugs were adsorbed to nanocages, the structure of nanocages and drugs changed after adsorption, indicating that the process was effective adsorption. The adsorption energy and solvation energy of the complexes created after adsorption were negative values, which indicated that the structure of complexes formed by adsorption were stable. According to charge decomposition analysis (CDA) and natural bonding orbitals (NBO), drugs act as charge donors and nanocages act as charge acceptors, so that the charge flows from drugs to nanocages. Thermodynamic calculations demonstrate that drugs adsorption on nanocages is a spontaneous exothermic process. The calculation of quantum molecular descriptors confirmed that drugs adsorption on nanocages increased the chemical reactivity and solubility of drugs, which facilitated its transfer in biological fluids. Both interaction region index (IRI) and topological analysis of atom in molecule (AIM) revealed Van Der Waals interaction between drugs and nanocages. Protonation studies demonstrated that acidic circumstances could improve the polarity of complexes, increase the solvation effect, and boost drugs release in target cancer cells. The results of this work indicate that X12N12(X = B, Al, Ga) nanocages can be used as the delivery vehicle of SF drug.Communicated by Ramaswamy H. Sarma.

Moderate binding of villin headpiece protein to C3N3 nanosheet reveals the suitable biocompatibility of this nanomaterial

Since its recent successful synthesis and due to its promising physical and chemical properties, the carbon nitrite nanomaterial, C3N3, has attracted considerable attention in various scientific areas. However, thus far, little effort has been devoted to investigating the structural influence of the direct interaction of this 2D nanomaterial and biomolecules, including proteins and biomembranes so as to understand the physical origin of its bio-effect, particularly from the molecular landscape. Such information is fundamental to correlate to the potential nanotoxicology of the C3N3 nanomaterial. In this work, we explored the potential structural influence of a C3N3 nanosheet on the prototypical globular protein, villin headpiece (HP35) using all-atom molecular dynamics (MD) simulations. We found that HP35 could maintain its native conformations upon adsorption onto the C3N3 nanosheet regardless of the diversity in the binding sites, implying the potential advantage of C3N3 in protecting the biomolecular structure. The adsorption was mediated primarily by vdW interactions. Moreover, once adsorbed on the C3N3 surface, HP35 remains relatively fixed on the nanostructure without a distinct lateral translation, which may aid in keeping the structural integrity of the protein. In addition, the porous topological structure of C3N3 and the special water layer present on the C3N3 holes conjointly contributed to the restricted motion of HP35 via the formation of a high free energy barrier and a steric hindrance to prevent the surface displacement. This work revealed for the first time the potential influence of the 2D C3N3 nanomaterial in the protein structure and provided the corresponding in-depth molecular-level mechanism, which is valuable for future applications of C3N3 in bionanomedicine.

State-of-the-art predictive modeling of heavy metal ions removal from the water environment using nanotubes

In this research, molecular dynamics (MD) simulation is used to investigate the efficiency of carbon nanotubes (CNT) and boron nitride nanotubes (BNNT) in removing lead ions from contaminated waters. Then the effect of functionalizing nanotubes with -COO- and COOH- functional groups and the nanotubes' absorption performance of two different concentrations of lead ions are studied. To better evaluate adsorption process, the set of descriptors, such as interaction energies, radial distribution function, etc., are calculated. The MD results show that the absorption performance is significantly improved by modifying the surface of CNT and BNNT with functional groups. In addition, the adsorption capacity increases in higher concentrations of Pb ions at BNNTCOO- and CNTCOOH systems. The interaction energy of BNNTCOO- with a concentration of 50 lead ions is - 2879.28 kJ/mol, which is about 106 kJ/mol more negative than BNNTCOO- at a concentration of 20 lead ions. Also, it is observed that the functionalization of both nanotubes with -COO- increases their absorption capacity. The obtained results from this study provide significant information about the mechanisms of lead adsorption on the surface of nanotubes.

Alginate/geopolymer hybrid beads as an innovative adsorbent applied to the removal of 5-fluorouracil from contaminated environmental water

Water contaminated by cytostatic drugs has many negative impacts on the ecosystems. In this work, cross-linked adsorbent beads based on alginate and a geopolymer (prepared from an illito-kaolinitic clay) were developed for a promising decontamination of the 5-fluorouracil (5-FU) cytostatic drug from water samples. The characterization of the prepared geopolymer and its hybrid derivative was performed by scanning electron microscopy, X-ray diffraction, Fourier transform infrared and termogravimetric analysis. Batch adsorption experiments indicated that alginate/geopolymer hybrid beads (AGHB) allow an excellent 5-FU removal efficiency of up to 80% for a dosage adsorbent/water of 0.002 g/mL and a concentration of 5-FU of 2.5 mg/L. The adsorption isotherms data follow well the Langmuir model. The kinetics data favor the pseudo-second-order model. The maximum adsorption capacity (q_max) was 6.2 mg/g. The optimal adsorption pH was 4. Besides pore filling sorption process, the carboxyl and hydroxyl groups from alginate immobilized onto the geopolymer matrix favored the retention of 5-FU ions by hydrogen bonds. Common competitors, such as dissolved organic matter, do not significantly affected the adsorption. In addition, this material has not only eco-friendly and cost-effective advantages but also excellent efficiency when applied to real environmental samples such as wastewater and surface water. This fact suggests that it could have a great application in the purification of contaminated water.

Molecular level insight into the different interaction intensity between microplastics and aromatic hydrocarbon in pure water and seawater

The interaction of MPs and aromatic hydrocarbons in seawater and pure water was examined using experimental measurements, molecular dynamics (MD) simulations, and density functional theory (DFT) calculations in light of the potential health risks posed by microplastic (MPs)-associated aromatic hydrocarbon pollutants. Isothermal studies and MD simulations suggested that MPs have a stronger affinity for aromatic hydrocarbons in seawater. To uncover the mechanism, MPs' surface characteristics and their intermolecular interactions with aromatic hydrocarbons were examined. According to the research, MPs in seawater have less compact structure, bigger pores, and a higher specific surface area, all of which contribute to more sorption sites. Analysis of the intermolecular interaction indicated that MPs have a greater ability for molecular interactions in seawater and the interaction energy between MPs and aromatic hydrocarbons in seawater is higher. Additionally, seawater cations may act as bridges, which also accelerate sorption in seawater. In summary, this study provides a molecular-level understanding of MPs-aromatic hydrocarbons interaction and demonstrates that the interaction is stronger in seawater.

In silico exploration of disulfide derivatives of Ferula foetida oleo-gum (Covexir®) as promising therapeutics against SARS-CoV-2

Although vaccines have been significantly successful against coronavirus, due to the high rate of the Omicron variant spread many researchers are trying to find efficient drugs against COVID-19. Herein, we conducted a computational study to investigate the binding mechanism of four potential inhibitors (including disulfide derivatives isolated from Ferula foetida) to SARS-CoV-2 main protease. Our findings revealed that the disulfides mainly interacted with HIS41, MET49, CYS145, HIS64, MET165, and GLN189 residues of SARS-CoV-2 main protease. The binding free energy decomposition results also showed that the van der Waals (vdW) energy plays the main role in the interaction of HIS41, MET49, CYS145, HIS64, MET165, and GLN189 residues with the inhibitors. Furthermore, it is found that the Z-isomer derivatives have a stronger interaction with SARS-CoV-2, and the strongest interaction belongs to the (Z)-1-(1-(methylthio)propyl)-2-(prop-1-enyl)disulfane (ΔG = -18.672 kcal/mol). The quantum mechanical calculations demonstrated that the second-order perturbation stabilization energy and the electron density values for MET49-ligand interactions are higher than the other residue-ligand complexes. This finding confirms the stronger interaction of this residue with the ligands.

Development of the poly(l-histidine) grafted carbon nanotube as a possible smart drug delivery vehicle

Polyhistidine is among the cell-penetrating peptides that in an acidic environment can facilitate membrane transition. Keeping in mind that the pH of the tumor intercellular medium is ∼5.5, in this paper, we examined the functionalization of a convenient drug delivery vehicle with cell-penetrating poly(l-histidine) to provide a smart drug delivery system. Classical molecular dynamics and metadynamics simulations are used to investigate the interactions between doxorubicin, carbon nanotube, poly(l-histidine), and the cell membrane. Metadynamics simulation revealed that not only the global minimum of FES reduced in an acidic environment but also the difference between the free energy of Doxorubicin as being adsorbed on poly(l-histidine) compared to when being freely dissolved in the aqueous medium show a dramatic reduction. MD simulations showed that functionalization of carbon nanotube with poly(l-histidine) groups has no detriment effect in the adsorption of Doxorubicin. The L-J interaction between Doxorubicin and carrier at the equilibrium states reached around -600 kJ/mol, both for the pristine and functionalized carbon nanotube. The coulombic interactions for both complexes were negligible in the neutral environment. At the acidic environment, the L-J interactions retained the same values as the neutral, while the coulombic interactions showed positive values, which suggested its participation in the detachments. At the vicinity of the membrane, the complexes retain their integrity both in neutral and acidic environments. In the present work, we performed metadynamics simulation to investigate the effects of poly(l-histidine) on the adsorption capacity of the carbon nanotubes, and explore the adsorption/desorption processed of Doxorubicin on pristine and poly(l-histidine)-grafted carbon nanotube. The resulted complexes were then subjected to interact with the POPC membrane model in both acidic and neutral environments via molecular dynamic simulations. The results provided here will hopefully help in a better understanding of future drug delivery systems and be helpful in designing more efficient and smart drug delivery systems.

Appraising the potency of small molecule inhibitors and their graphene surface-mediated organizational attributes on uric acid-melamine clusters

Uric acid (UA) and melamine (MM) crystallization in humans is associated with adverse medical conditions, including the germination of kidney stones, because of their low solubility. The growth of kidney stones, usually formed on renal papillary facades, is accomplished on the matrix-coated surface by the aggregation of preformed crystals or secondary crystal nucleation. Therefore, the effects of inhibitors such as theobromine (TB) and allopurinol (AP) on MM-UA aggregation are investigated by employing classical molecular dynamics simulations on a graphene surface. This impersonates the exact essence of the precipitation of kidney stones. The interaction between MM-UA is very intense and, thus, large clusters are formed on the surface. The presence of TB and AP will, however, substantially inhibit their aggregation. TB and AP significantly impede UA aggregation in particular. Therefore, lower order UA clusters are formed. These smaller UA clusters then pull a lower number of MM towards themselves, resulting in a smaller order UA-MM cluster. MM and UA aggregation on a 2D graphene surface is found to be spontaneous. There is no difference in these molecules' adsorption with a change in the force field parameters (i.e., GAFF and OPLS-AA) for graphene. Moreover, the greater the surface area of graphene, the more molecules are absorbed. The solute-surface van der Waals interaction energy plays a driving force in the adsorption of solute molecules on the surface. In addition, interactions like hydrogen bonding and π-stacking over the graphene surface involve binding all like molecules. These aggregated solute molecules strongly attract more like molecules until all solute molecules are adsorbed on the graphene surface, as estimated by enhanced sampling. The molecular origin of graphene exfoliation by MM is also described here. The present work helps to design novel kidney stone inhibitors.

Surface functionalization of boron nitride nanosheet with folic acid: Toward an enhancement in Doxorubicin anticancer drug loading performance

Loading of the Doxorubicin (DOX) as an anticancer drug molecule on boron nitride (BN) nanosheets with different sizes, in the presence and absence of Folic Acid (FA) functional groups, are investigated using molecular dynamic simulations. The obtained results from these investigations revealed that the drug molecules are spontaneously adsorbed the carriers and form stable complexes. It is also shown that an increase the nanosheet leads to an enhancement in its capacity to adsorb the drugs. Furthermore, the conjugation of BN with the FA group not only improves the BN efficiency for the drug adsorption but also helps the drug-carrier complex to target the cancerous cells. Evaluation of interaction energies reveals that L-J interaction plays an essential role in the adsorption of the drug molecules on the BN. The radial distribution function (RDF) shows that the highest drug position probability is around 0.6 nm away from the BN surface. Atomic RDF analysis is in line with the interaction energy analysis and proved that π-π stacking contributes the most to this process. Hydrogen bond (HB) analysis also shows that, although limited, the columbic interaction can be helpful in the adsorption process. Moreover, the free energy (FE) surface is explored for a system containing a BN nanosheet, an FA group, and a DOX molecule through metadynamics simulations. The obtained results reveal that the lowest FE point located in coordinations d1 = 0.70 nm and d2 = 0.84 nm, and energetically reached -280.42 kJ/mol. It can be concluded from the FE calculations that while the FA is stuck on the substrate, DOX faces difficulty in the way it be adsorbed. In return, it will be hard for the molecule to be released from the BN surface through desorption processes in neutral pH because it faces an energy barrier with a height of ∼100 kJ/mol at 1.6 nm.

Molecular interpretation of the carbon nitride performance as a template for the transport of anti-cancer drug into the biological membrane

Evaluation of interaction mechanism between 2-dimensional (2D) nanomaterials and cell membranes is a critical issue in providing guidelines for biomedical applications. Recent progress in computer-aided molecular design tools, especially molecular dynamics (MD) simulation, afford a cost-effective approach to achieving this goal. In this work, based on this hypothesis, by utilizing theoretical methods including MD simulation and free energy calculations, a process is evaluated in which the Doxorubicin (DOX)-loaded onto carbon nitride (CN) nanosheet faced with bilayer membrane. It should be mentioned that to achieve an efficient CN-based drug delivery system (DDS), in the first place, the intermolecular interaction between the carrier and DOX is investigated. The obtained results show that the DOX prefers a parallel orientation with respect to the CN surface via the formation of π-π stacking and H-bond interactions. Furthermore, the adsorption energy value between the drug and the carrier is evaluated at about - 312 kJ/mol. Moreover, the investigation of the interaction between the CN-DOX complex and the membrane reveals that due to the presence of polar heads in the lipid bilayer, the contribution of electrostatic energy is higher than the van der Waals energy. The global minimum in free energy surface of the DDS is located between the head groups of the cell membrane. Overall, it can be concluded that the CN nanosheet is a suitable candidate for transfer and stabilize DOX on the membrane.

Insight into Organic Pollutant Adsorption Characteristics on a g-C3N4 Surface by Attenuated Total Reflection Spectroscopy and Molecular Dynamics Simulation

Herein the adsorption characteristics of zwitterionic dye pollutant Rhodamine B (Rh⁺B^-) on a g-C₃N₄ surface were investigated by both an attenuated total reflection spectroscopy (ATRS) experiment and a molecular dynamics simulation (MDS). For experimental investigation, g-C₃N₄ was coated on a silica optical fiber (SOF) surface to fabricate an adsorption film. According to the ATRS response, adsorption thermodynamics and thermodynamics results were in situ obtained and evaluated. The isothermal Langmuir model was used to calculate the adsorption equilibrium constants (K_ads) and adsorption energies (ΔG_ads) for Rh⁺B^- as 27.25 × 10⁴ M^-1 and -31.01 kJ mol^-1, respectively, which indicated the spontaneous adsorption behavior of Rh⁺B^- at the g-C₃N₄ surface. Using dynamic Elovich modeling, the rate constants of Rh⁺B^- were found to be k₁ = 0.0063 min^-1 and k₂ = 0.0004 min^-1, which indicated two-stage adsorption at the g-C₃N₄ surface. For theoretical simulation, adsorption configurations and adsorption energies were systematically calculated by a molecular dynamics simulation (MDS) . Rh⁺B^- molecules were inclined to orient in a parallel position at the g-C₃N₄ surface during low concentration but a perpendicular position at the g-C₃N₄ surface during high concentration. Combined with experimental and calculation results, this work revealed the microscopic adsorption performance and elucidated the intermolecular interaction between localized interfaces of g-C₃N₄ and hazardous dye pollutant. We propose an adsorption model to explain the process of surface interaction, which is based on molecular orientation and a force-driven mechanism. Electrostatic attraction and π-π interaction dominated the adsorption interaction with an adsorption energy of ΔG_low(ads) = -38.96 kJ mol^-1 for low Rh⁺B^- concentration, and electrostatic attraction dominated the adsorption interaction with an adsorption energy of ΔG_high(ads) = -25.76 kJ mol^-1 for high Rh⁺B^- concentration. This work can provide a fundamental basis for a dye-pollutants removal application by g-C₃N₄ in both adsorption and photocatalyzation.

Exploring pH dependent delivery of 5-fluorouracil from functionalized multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) can be applied for pH-sensitive delivery of anticancer drugs. Due to the importance of 5-fluorouracil (5-FU) in different tumor therapy regimens, it has been widely used in different pH dependent drug delivery systems. To investigate the pH effects on loading (and release) of 5-FU on (and from) the functionalized MWCNTs and propose the optimum condition for drug delivery, both macroscopic and microscopic studies were carried out using chromatography and molecular dynamic simulation at different conditions. For both levels of studies, different analytical approaches were performed to assess the validity of the methods. The experimental results revealed that 5-FU has more binding affinity to the surface of the nanocarrier at physiological pH (pH = 7.4) and showed more release at acidic conditions (pH = 5.0). Meanwhile it has been observed that basic pH (pH = 9.0) can lead to a dramatic decrease effect on loading of the drug. The results of this study can be used to suggest the optimum pH levels for nanocarbon based formulations of 5-FU in cancer therapy.

Mild adsorption of carbon nitride (C3N3) nanosheet on a cellular membrane reveals its suitable biocompatibility

Recently, the novel hole-containing carbon nitride C₃N₃ nanomaterial was successfully synthesized, featuring outstanding and unique mechanical and electrical properties. However, to fully exploit this nanomaterial in biomedical applications, information regarding its biocompatibility is necessary. Herein, by using all-atom molecular dynamics simulations, we evaluate the interactions between a C₃N₃ nanosheet and a critical cellular component, that is, a lipid membrane bilayer. Our results indicate that the C₃N₃ nanosheet is able to interact with the lipid bilayer surface without affecting the membrane's structural integrity. Moreover, our results showed that the C₃N₃ nanosheet is adsorbed on the surface of the lipid bilayer without inflicting any structural damage to the membrane, regardless of the conditions of the system (that is, with and without restrains in the C₃N₃ nanosheet). Also, we found that both energy contributions, namely vdW and Coulomb energies, conjointly mediated the C₃N₃ adsorption process. In comparison and as expected, pristine graphene significantly disturbed the membrane structure. Perpendicularly-oriented-sheet simulations described the significance of the surface charges of the C₃N₃ nanosheet in prohibiting its insertion into the membrane. Detailed analysis indicated that the electrostatic attraction between the pores in the C₃N₃ structure and the lipid head amino groups stabilized the interaction restricting the insertion of the C₃N₃ structure deeper into the membrane. Our results suggested the importance of the negatively charged C₃N₃ pores when interacting with lipid membranes. Our findings shed light on the potential compatibility of C₃N₃ with biomembranes and its underlying molecular mechanism, which might provide a useful foundation for the future exploration of this 2D nanomaterial in biomedical applications.

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.

Assessment of the effect of external and internal triggers on adsorption and release of paclitaxel from the PEI functionalized silicene nanosheet: A molecular dynamic simulation

In order to examine the adsorption mechanisms of paclitaxel (PTX) on silicene nanosheet (SNS) molecular dynamics (MD) simulations are carried out. The MD outcomes show that the adsorption of PTX on the pristine SNS is exothermic and spontaneous. The interaction between the PTX molecule and the pristine SNS is mainly due to the formation of π-π interactions through their aromatic rings, which are supplemented by X-π (X = N-H, C-H, and CO) interactions. Upon functionalization of SNS by Polyethylenimine (PEI), drug molecules prefer to bind to the nanocarrier instead of the polymer. In the functionalized SNS (f-SNS), the binding energy of the drug with the nanocarrier becomes stronger in comparison to the SNS case (E_ads: -2468.91 vs -840.95 kJ/mol). At the acidic condition, protonation of drug and PEI cause that the interaction between PTX and the nanocarrier become weaker and drug molecules could release from the nanocarrier surface. Finally, two f-SNS and protonated f-SNS (f-pSNS) systems are induced by the electric field (EF). Evaluation of the dynamic properties of these systems (with strengths 0.5 and 1 V/nm) shows that the electric field could be acted as a stimulus for drug release from nanocarriers. The obtained results from this study provide valuable information about the loading/release mechanisms of PTX on/from the SNS surface.

Design of new drug delivery platform based on surface functionalization of black phosphorus nanosheet with a smart polymer for enhancing the efficiency of doxorubicin in the treatment of cancer

The development of drug delivery systems (DDSs) has raised hopes for targeted cancer therapy. Smart polymers can be conjugated with several nanoparticles and increase their efficiency in biomedical applications. In this work, the classical molecular dynamics and well-tempered metadynamics simulations are performed to study the behavior of black phosphorus (BPH) nanosheet functionalized with polyethylenimine (PEI) in adsorption, diffusion, and release of doxorubicin (DOX) anticancer drug. Adsorption of the drug on PEI-BPH surface is mainly due to the formation of strong pi-pi interaction between the drug and BPH. The drug-binding to the nanosheet is enhanced by the intermolecular hydrogen bond that formed between DOX and PEI. The energy values for the interaction of DOX with BPH and PEI are calculated to be about - 180 and - 50 kJ/mol, respectively. The obtained results indicated that the adsorption of the drug molecules on the nanosheet destroyed the hydration layer around the BPH-PEI surface. The free energy calculation for DDS shows a global minimum in which the distances of DOX from BPH surface and PEI are about 1.0 and 0.5 nm, respectively. Furthermore, the diffusion of DDS into the membrane has a macropinocytosis pathway that is in line with experimental observations. Moreover, it is found that, unlike the isolated DOX, the drug in complex with BPH-PEI can be easily penetrated membrane cells. The study of the pH-responsive release of the drug shows the high solubility of the polymer in the water environment plays the main role in swelling of DDS and the release of the DOX molecules.

Development and evaluation of a pH-responsive and water-soluble drug delivery system based on smart polymer coating of graphene nanosheets: an in silico study

The objective of this study is to develop a controlled and water-soluble delivery system for doxorubicin (DOX) based on the coating of graphene (G) with a smart polymer. A combination of polyethyleneimine (PEI) and G–DOX is investigated by performing density functional theory (DFT) calculations and molecular dynamics (MD) simulations. Several parameters have been employed to evaluate the effect of PEI on the adsorption and release mechanisms of DOX. The obtained results indicated that the binding energy of the drug molecule on G in the presence of PEI is enhanced by about 20% under neutral conditions, whereas the drug absorption becomes weaker in an acidic environment so that DOX could be separated from the carrier surface using near-infrared radiation (NIR). Based on the atom in molecule (AIM) theory, two hydrogen bonds with strengths of about −12.59 and −39.99 kJ mol⁻¹ have been established. Furthermore, evaluating the dynamic behavior of the designed systems in water solution shows that the polymer in physiological pH rapidly adsorbed on the drug–carrier complex. However, at acidic pH, it is quickly desorbed from the carrier surface and the G–DOX complex can be exposed to cancer cells. The obtained results of the present research may be used in future experimental work to design smart DDSs.

The objective of this study is to develop a controlled and water-soluble delivery system for doxorubicin (DOX) based on the coating of graphene (G) with a smart polymer.