Development of "on-demand" thermo-responsive hydrogels for anti-cancer drugs sustained release: Rational design, in silico prediction and in vitro validation in colon cancer models.

A rational design accurate based on the use of Statistical Design of the Experiments (DoE) and Molecular Dynamics Simulations Studies allows the prediction and the understanding of thermo-responsive hydrogels prepared regarding their gelation temperature and anti-cancer drug release rate. N-isopropylacrilamide (NIPAM) modified with specific co-monomers and crosslinkers, can be used to prepare "on-demand" thermo-responsive hydrogels with the ideal properties for clinical applications in which local sustained release of drugs is crucial. Two preferential formulations resulting from the predictive studies of DoE and In Silico methods were synthesized by radical polymerization, fully characterized, and loaded with the anticancer drug Doxorubicin (Dox). The hydrogel formulations were characterized by swelling rate, turbidity, FTIR, 1H NMR, SEM, gelation time, rheology, and biocompatibility assays. Both formulations demonstrated adequate morphologic, rheological, and biocompatibility properties; however, important differences in terms of drug retention were detected. As demonstrated by a Dox cumulative release study and posteriorly confirmed by an efficacy assay in an in vitro colorectal cancer model, the formulation composed by NIPAM and 4-penten-1-ol crosslinked with poly(ethylene glycol) diacrylate (PEGDA) (PNiPenPH) present a slow release over the time, presenting ideal properties to become and ideal depot system for the local sustained release of anticancer drugs as adjuvant therapy or in the case of non-resectable tumors.

Effect of the Generation of PAMAM Dendrimers on the Stabilization of Gold Nanoparticles.

The behavior of small and intermediate generations of poly(amidoamine) (PAMAM) dendrimers and PAMAM|gold nanocomposites was studied by computational tools and experimental techniques. Molecular dynamics simulations were used to characterize at the atomic level the stabilization mechanism of gold nanoparticles by dendrimeric platforms. Low PAMAM generations create a stabilization sphere around the nanoparticle, while upper PAMAM sizes provide stabilization sites through the internal voids. These results can help in the understanding of the stabilization process of metallic nanoparticles for the design and contribution of new nanotechnological applications.

An Overview of Injectable Thermo-Responsive Hydrogels and Advances in their Biomedical Applications.

BACKGROUND: Injectable hydrogels are a thermo-responsive system based on biomaterials. Injectable hydrogels have been broadly investigated mainly as vehicles or scaffolds of therapeutic agents that include drugs, proteins, cells, and bioactive molecules among others, utilized in the treatment of diseases such as cancers and the repair and regeneration of tissues. RESULTS: There are several studies that have described the multiple features of hydrogels. However, the main aspect that breaks the paradigm in the application of hydrogels is the thermoresponsiveness that some of them have, which is an abrupt modification in their properties in response to small variations in temperature. For that reason, the thermo-responsive hydrogels with the unique property of sol-gel transition have received special attention over the past decades. These hydrogels show phase transition near physiological human body temperature. This feature is key for being applied in promising areas of human health-related research. CONCLUSION: The purpose of this study is the overview of injectable hydrogels and their latest advances in medical applications including bioactive compound delivery, tissue engineering, and regenerative medicine.

Film Dressings Based on Hydrogels: Simultaneous and Sustained-Release of Bioactive Compounds with Wound Healing Properties.

This research proposes the rational modeling, synthesis and evaluation of film dressing hydrogels based on polyvinyl alcohol crosslinked with 20 different kinds of dicarboxylic acids. These formulations would allow the sustained release of simultaneous bioactive compounds including allantoin, resveratrol, dexpanthenol and caffeic acid as a multi-target therapy in wound healing. Interaction energy calculations and molecular dynamics simulation studies allowed evaluating the intermolecular affinity of the above bioactive compounds by hydrogels crosslinked with the different dicarboxylic acids. According to the computational results, the hydrogels crosslinked with succinic, aspartic, maleic and malic acids were selected as the best candidates to be synthesized and evaluated experimentally. These four crosslinked hydrogels were prepared and characterized by FTIR, mechanical properties, SEM and equilibrium swelling ratio. The sustained release of the bioactive compounds from the film dressing was investigated in vitro and in vivo. The in vitro results indicate a good release profile for all four analyzed bioactive compounds. More importantly, in vivo experiments suggest that prepared formulations could considerably accelerate the healing rate of artificial wounds in rats. The histological studies show that these formulations help to successfully reconstruct and thicken epidermis during 14 days of wound healing. Moreover, the four film dressings developed and exhibited excellent biocompatibility. In conclusion, the novel film dressings based on hydrogels rationally designed with combinatorial and sustained release therapy could have significant promise as dressing materials for skin wound healing.

Binding and Catalytic Mechanisms of Veratryl Alcohol Oxidation by Lignin Peroxidase: A Theoretical and Experimental Study.

Lignin peroxidase (LiP) and its natural substrate veratryl alcohol (VA) play a crucial role in lignin degradation by white-rot fungi. Understanding the molecular determinants for the interaction of this enzyme with its substrates is essential in the rational design of engineered peroxidases for biotechnological application. Here, we combine computational and experimental approaches to analyze the interaction of Phanerochaete chrysosporium LiP (isoenzyme H8) with VA and its radical cation (VA•+, resulting from substrate oxidation by the enzyme). Interaction energy calculations at semiempirical quantum mechanical level (SQM) between LiP and VA/VA•+ enabled to identify those residues at the acidic environment of catalytic Trp171 involved in the main interactions. Then, a battery of variants, with single and multiple mutations at these residues (Glu168, Asp165, Glu250, Asp264, and Phe267), was generated by directed mutagenesis, and their kinetics parameters were estimated on VA and two additional substrates. The experimental results show that Glu168 and Glu250 are crucial for the binding of VA, with Glu250 also contributing to the turnover of the enzyme. The experimental results were further rationalized through new calculations of interaction energies between VA/VA•+ and LiP with each of the single mutations. Finally, the delocalization of spin density was determined with quantum mechanics/molecular mechanics calculations (QM/MM), further supporting the contribution of Glu250 to VA oxidation at Trp171.

Rational Design, Synthesis and Evaluation of γ-CD-Containing Cross-Linked Polyvinyl Alcohol Hydrogel as a Prednisone Delivery Platform.

This study describes the in-silico rational design, synthesis and evaluation of cross-linked polyvinyl alcohol hydrogels containing γ-cyclodextrin (γ-CDHSAs) as platforms for the sustained release of prednisone (PDN). Through in-silico studies using semi-empirical quantum mechanical calculations, the effectiveness of 20 dicarboxylic acids to generate a specific cross-linked hydrogel capable of supporting different amounts of γ-cyclodextrin (γ-CD) was evaluated. According to the interaction energies calculated with the in-silico studies, the hydrogel made from PVA cross-linked with succinic acids (SA) was shown to be the best candidate for containing γ-CD. Later, molecular dynamics simulation studies were performed in order to evaluate the intermolecular interactions between PDN and three cross-linked hydrogel formulations with different proportions of γ-CD (2.44%, 4.76% and 9.1%). These three cross-linked hydrogels were synthesized and characterized. The loading and the subsequent release of PDN from the hydrogels were investigated. The in-silico and experimental results showed that the interaction between PDN and γ-CDHSA was mainly produced with the γ-CDs linked to the hydrogels. Thus, the unique structures and properties of γ-CDHSA demonstrated an interesting multiphasic profile that could be utilized as a promising drug carrier for controlled, sustained and localized release of PDN.

In-Silico Design, Synthesis and Evaluation of a Nanostructured Hydrogel as a Dimethoate Removal Agent.

This study describes the in-silico design, synthesis, and evaluation of a cross-linked PVA hydrogel (CLPH) for the absorption of organophosphorus pesticide dimethoate from aqueous solutions. The crosslinking effectiveness of 14 dicarboxilic acids was evaluated through in-silico studies using semiempirical quantum mechanical calculations. According to the theoretical studies, the nanopore of PVA cross-linked with malic acid (CLPH-MA) showed the best interaction energy with dimethoate. Later, using all-atom molecular dynamics simulations, three hydrogels with different proportions of PVA:MA (10:2, 10:4, and 10:6) were used to evaluate their interactions with dimethoate. These results showed that the suitable crosslinking degree for improving the affinity for the pesticide was with 20% (W%) of the cross-linker. In the experimental absorption study, the synthesized CLPH-MA20 recovered 100% of dimethoate from aqueous solutions. Therefore, the theoretical data were correlated with the experimental studies. Surface morphology of CLPH-MA20 by Scanning Electron Microscopy (SEM) was analyzed. In conclusion, the ability of CLPH-MA20 to remove dimethoate could be used as a technological alternative for the treatment of contaminated water.

Rational Development of a Novel Hydrogel as a pH-Sensitive Controlled Release System for Nifedipine.

This work depicts the rational development (in-silico design, synthesis, characterization and in-vitro evaluation) of polyvinyl alcohol hydrogels (PVAH) cross-linked with maleic acid (MA) and linked to γ-cyclodextrin molecules (γ-CDPVAHMA) as systems for the controlled and sustained release of nifedipine (NFD). Through computational studies, the structural blocks (PVA chain + dicarboxylic acid + γ-CD) of 20 different hydrogels were evaluated to test their interaction energies (ΔE) with NFD. According to the ΔE obtained, the hydrogel cross-linked with maleic acid was selected. To characterize the intermolecular interactions between NFD and γ-CDPVAHMA, molecular dynamics simulation studies were carried out. Experimentally, three hydrogel formulations with different proportions of γ-CD (2.43%, 3.61% and 4.76%) were synthesized and characterized. Both loading and release of NFD from the hydrogels were evaluated at acid and basic pH. The computational and experimental results show that γ-CDs linked to the hydrogels were able to form 1:1 inclusion complexes with NFD molecules. Finally, γ-CDPVAHMA-3 demonstrated to be the best pH-sensitive release platform for nifedipine. Its effectiveness could significantly reduce the adverse effects caused by the anticipated release of NFD in the stomach of patients.

New polymer for removal of wine phenolics: Poly(N-(3-(N-isobutyrylisobutyramido)-3-oxopropyl)acrylamide) (P-NIOA).

The phenolic compounds of wine contribute to color and astringency, also are responsible for the oxidation state and bitterness. Due the importance of these molecules, different techniques have been used to modulate their concentration such as natural or synthetic polymeric agents. Among the polymeric agents, PVPP is one of the most used, but lacks of selectivity and has a limited pH range. Therefore, the aim of this study was the synthesis of a new polymer, poly(N-(3-(N-isobutyrylisobutyramido)-3-oxopropyl)acrylamide) (P-NIOA), for removal of phenolic compounds, as a potential agent for the fining of wine. The new polymer affinity was studied using HPLC-DAD for different polyphenols using PVPP as a control. The results showed that the new polymer has a similar removal as PVPP, but with lower affinity to resveratrol. The interactions established between polymers and polyphenols were studied using computational chemistry methods demonstrating a direct correlation with the experimental affinity data.

Experimental and theoretical binding affinity between polyvinylpolypyrrolidone and selected phenolic compounds from food matrices.

Polyvinylpolypyrrolidone (PVPP) is a fining agent, widely used in winemaking and brewing, whose mode of action in removing phenolic compounds has not been fully characterised. The aim of this study was to evaluate the experimental and theoretical binding affinity of PVPP towards six phenolic compounds representing different types of phenolic species. The interaction between PVPP and phenolics was evaluated in model solutions, where hydroxyl groups, hydrophobic bonding and steric hindrance were characterised. The results of the study indicated that PVPP exhibits high affinity for quercetin and catechin, moderate affinity for epicatechin, gallic acid and lower affinity for 4-methylcatechol and caffeic acid. The affinity has a direct correlation with the hydroxylation degree of each compound. The results show that the affinity of PVPP towards phenols is related with frontier orbitals. This work demonstrates a direct correlation between the experimental affinity and the interaction energy calculations obtained through computational chemistry methods.

Study of interaction energies between the PAMAM dendrimer and nonsteroidal anti-inflammatory drug using a distributed computational strategy and experimental analysis by ESI-MS/MS.

The structure of a dendrimer exhibits a large number of internal and superficial cavities, which can be exploited, to capture and deliver small organic molecules, enabling their use in drug delivery. Structure-based modeling and quantum mechanical studies can be used to accurately understand the interactions between functionalized dendrimers and molecules of pharmaceutical and industrial interest. In this study, we implemented a Metropolis Monte Carlo algorithm to calculate the interaction energy of dendrimer-drug complexes, which can be used for in silico prediction of dendrimer-drug affinity. Initially, a large-scale sampling of different dendrimer-drug conformations was generated using Euler angles. Then, each conformation was distributed on different nodes of a GRID computational system, where its interaction energy was calculated by semiempirical quantum mechanical methods. These energy calculations were performed for four different nonsteroidal anti-inflammatory drugs, each showing different affinities for the PAMAM-G4 dendrimer. The affinities were also characterized experimentally by using Cooks' kinetic method to calculate PAMAM-drug dissociation constants. The quantitative structure-activity relationship between the interaction energies and dissociation constants showed statistical correlations with r(2) > 0.9.