Molecules

Editorial

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4 pages, 186 KiB

Open AccessEditorial

Special Issue: “Smart and Functional Polymers”

by Xiangru Feng, Mingqiang Li, Yang Li and Jianxun Ding

Molecules 2019, 24(16), 2976; https://doi.org/10.3390/molecules24162976 - 16 Aug 2019

Cited by 4 | Viewed by 3534

Abstract

Polymerization provides an efficient strategy for synthesizing macromolecules with versatile functionality [...] Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

Research

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14 pages, 4948 KiB

Open AccessFeature PaperArticle

PEGylated Polyurea Bearing Hindered Urea Bond for Drug Delivery

by Meishan Chen, Xiangru Feng, Weiguo Xu, Yanqiao Wang, Yanan Yang, Zhongyu Jiang and Jianxun Ding

Molecules 2019, 24(8), 1538; https://doi.org/10.3390/molecules24081538 - 18 Apr 2019

Cited by 10 | Viewed by 3732

Abstract

In recent years, polyureas with dynamic hindered urea bonds (HUBs), a class of promising biomedical polymers, have attracted wide attention as a result of their controlled hydrolytic properties. The effect of the chemical structures on the properties of polyureas and their assemblies has [...] Read more.

In recent years, polyureas with dynamic hindered urea bonds (HUBs), a class of promising biomedical polymers, have attracted wide attention as a result of their controlled hydrolytic properties. The effect of the chemical structures on the properties of polyureas and their assemblies has rarely been reported. In this study, four kinds of polyureas with different chemical groups have been synthesized, and the polyureas from cyclohexyl diisocyanate and tert-butyl diamine showed the fastest hydrolytic rate. The amphiphilic polyurea composed of hydrophobic cyclohexyl-tert-butyl polyurea and hydrophilic poly(ethylene glycol) (PEG) was synthesized for the controlled delivery of the antitumor drug paclitaxel (PTX). The PTX-loaded PEGylated polyurea micelle more effectively entered into the murine breast cancer 4T1 cells and inhibited the corresponding tumor growth in vitro and in vivo. Therefore, the PEGylated polyurea with adjustable degradation might be a promising polymer matrix for drug delivery. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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13 pages, 1463 KiB

Open AccessArticle

Structure Characterization and Otoprotective Effects of a New Endophytic Exopolysaccharide from Saffron

by Juan Li, Guimei Wu, Cuiying Qin, Wuhai Chen, Gang Chen and Lu Wen

Molecules 2019, 24(4), 749; https://doi.org/10.3390/molecules24040749 - 19 Feb 2019

Cited by 16 | Viewed by 3365

Abstract

Saffron, a kind of rare medicinal herb with antioxidant, antitumor, and anti-inflammatory activities, is the dry stigma of Crocus sativus L. A new water-soluble endophytic exopolysaccharide (EPS-2) was isolated from saffron by anion exchange chromatography and gel filtration. The chemical structure was characterized [...] Read more.

Saffron, a kind of rare medicinal herb with antioxidant, antitumor, and anti-inflammatory activities, is the dry stigma of Crocus sativus L. A new water-soluble endophytic exopolysaccharide (EPS-2) was isolated from saffron by anion exchange chromatography and gel filtration. The chemical structure was characterized by FT-IR, GC-MS, and 1D and 2D-NMR spectra, indicating that EPS-2 has a main backbone of (1→2)-linked α-d-Manp, (1→2, 4)-linked α-d-Manp, (1→4)-linked α-d-Xylp, (1→2, 3, 5)-linked β-d-Araf, (1→6)- linked α-d-Glcp with α-d-Glcp-(1→ and α-d-Galp-(1→ as sidegroups. Furthermore, EPS-2 significantly attenuated gentamicin-induced cell damage in cultured HEI-OC1 cells and increased cell survival in zebrafish model. The results suggested that EPS-2 could protect cochlear hair cells from ototoxicity exposure. This study could provide new insights for studies on the pharmacological mechanisms of endophytic exopolysaccharides from saffron as otoprotective agents Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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10 pages, 2505 KiB

Open AccessFeature PaperArticle

Rare Earth Hydroxide as a Precursor for Controlled Fabrication of Uniform β-NaYF₄ Nanoparticles: A Novel, Low Cost, and Facile Method

by Lili Xu, Man Wang, Qing Chen, Jiajia Yang, Wubin Zheng, Guanglei Lv, Zewei Quan and Chunxia Li

Molecules 2019, 24(2), 357; https://doi.org/10.3390/molecules24020357 - 19 Jan 2019

Cited by 5 | Viewed by 4341

Abstract

In recent years, rare earth doped upconversion nanocrystals have been widely used in different fields owing to their unique merits. Although rare earth chlorides and trifluoroacetates are commonly used precursors for the synthesis of nanocrystals, they have certain disadvantages. For example, rare earth [...] Read more.

In recent years, rare earth doped upconversion nanocrystals have been widely used in different fields owing to their unique merits. Although rare earth chlorides and trifluoroacetates are commonly used precursors for the synthesis of nanocrystals, they have certain disadvantages. For example, rare earth chlorides are expensive and rare earth trifluoroacetates produce toxic gases during the reaction. To overcome these drawbacks, we use the less expensive rare earth hydroxide as a precursor to synthesize β-NaYF₄ nanoparticles with multiform shapes and sizes. Small-sized nanocrystals (15 nm) can be obtained by precisely controlling the synthesis conditions. Compared with the previous methods, the current method is more facile and has lower cost. In addition, the defects of the nanocrystal surface are reduced through constructing core–shell structures, resulting in enhanced upconversion luminescence intensity. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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17 pages, 9921 KiB

Open AccessArticle

Fluoropolymer-Containing Opals and Inverse Opals by Melt-Shear Organization

by Julia Kredel, Christian Dietz and Markus Gallei

Molecules 2019, 24(2), 333; https://doi.org/10.3390/molecules24020333 - 17 Jan 2019

Cited by 12 | Viewed by 5434

Abstract

The preparation of highly ordered colloidal architectures has attracted significant attention and is a rapidly growing field for various applications, e.g., sensors, absorbers, and membranes. A promising technique for the preparation of elastomeric inverse opal films relies on tailored core/shell particle architectures and [...] Read more.

The preparation of highly ordered colloidal architectures has attracted significant attention and is a rapidly growing field for various applications, e.g., sensors, absorbers, and membranes. A promising technique for the preparation of elastomeric inverse opal films relies on tailored core/shell particle architectures and application of the so-called melt-shear organization technique. Within the present work, a convenient route for the preparation of core/shell particles featuring highly fluorinated shell materials as building blocks is described. As particle core materials, both organic or inorganic (SiO₂) particles can be used as a template, followed by a semi-continuous stepwise emulsion polymerization for the synthesis of the soft fluoropolymer shell material. The use of functional monomers as shell-material offers the possibility to create opal and inverse opal films with striking optical properties according to Bragg’s law of diffraction. Due to the presence of fluorinated moieties, the chemical resistance of the final opals and inverse opals is increased. The herein developed fluorine-containing particle-based films feature a low surface energy for the matrix material leading to good hydrophobic properties. Moreover, the low refractive index of the fluoropolymer shell compared to the core (or voids) led to excellent optical properties based on structural colors. The herein described fluoropolymer opals and inverse opals are expected to pave the way toward novel functional materials for application in fields of coatings and optical sensors. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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30 pages, 7832 KiB

Open AccessArticle

Candidate Polyurethanes Based on Castor Oil (Ricinus communis), with Polycaprolactone Diol and Chitosan Additions, for Use in Biomedical Applications

by Yomaira L. Uscátegui, Luis E. Díaz, José A. Gómez-Tejedor, Ana Vallés-Lluch, Guillermo Vilariño-Feltrer, María A. Serrano and Manuel F. Valero

Molecules 2019, 24(2), 237; https://doi.org/10.3390/molecules24020237 - 10 Jan 2019

Cited by 30 | Viewed by 6329

Abstract

Polyurethanes are widely used in the development of medical devices due to their biocompatibility, degradability, non-toxicity and chemical versatility. Polyurethanes were obtained from polyols derived from castor oil, and isophorone diisocyanate, with the incorporation of polycaprolactone-diol (15% w/w) and chitosan [...] Read more.

Polyurethanes are widely used in the development of medical devices due to their biocompatibility, degradability, non-toxicity and chemical versatility. Polyurethanes were obtained from polyols derived from castor oil, and isophorone diisocyanate, with the incorporation of polycaprolactone-diol (15% w/w) and chitosan (3% w/w). The objective of this research was to evaluate the effect of the type of polyol and the incorporation of polycaprolactone-diol and chitosan on the mechanical and biological properties of the polyurethanes to identify the optimal ones for applications such as wound dressings or tissue engineering. Polyurethanes were characterized by stress-strain, contact angle by sessile drop method, thermogravimetric analysis, differential scanning calorimetry, water uptake and in vitro degradation by enzymatic processes. In vitro biological properties were evaluated by a 24 h cytotoxicity test using the colorimetric assay MTT and the LIVE/DEAD kit with cell line L-929 (mouse embryonic fibroblasts). In vitro evaluation of the possible inflammatory effect of polyurethane-based materials was evaluated by means of the expression of anti-inflammatory and proinflammatory cytokines expressed in a cellular model such as THP-1 cells by means of the MILLIPLEX^® MAP kit. The modification of polyols derived from castor oil increases the mechanical properties of interest for a wide range of applications. The polyurethanes evaluated did not generate a cytotoxic effect on the evaluated cell line. The assessed polyurethanes are suggested as possible candidate biomaterials for wound dressings due to their improved mechanical properties and biocompatibility. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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11 pages, 2271 KiB

Open AccessFeature PaperArticle

Synthesis of Carbohydrate-Grafted Glycopolymers Using a Catalyst-Free, Perfluoroarylazide-Mediated Fast Staudinger Reaction

by William Ndugire, Bin Wu and Mingdi Yan

Molecules 2019, 24(1), 157; https://doi.org/10.3390/molecules24010157 - 3 Jan 2019

Cited by 12 | Viewed by 4556

Abstract

Glycopolymers have gained increasing importance in investigating glycan-lectin interactions, as drug delivery vehicles and in modulating interactions with proteins. The synthesis of these glycopolymers is still a challenging and rigorous exercise. In this regard, the highly efficient click reaction, copper (I)-catalyzed alkyne-azide cycloaddition, [...] Read more.

Glycopolymers have gained increasing importance in investigating glycan-lectin interactions, as drug delivery vehicles and in modulating interactions with proteins. The synthesis of these glycopolymers is still a challenging and rigorous exercise. In this regard, the highly efficient click reaction, copper (I)-catalyzed alkyne-azide cycloaddition, has been widely applied not only for its efficiency but also for its tolerance of the appended carbohydrate groups. However, a significant drawback of this method is the use of the heavy metal catalyst which is difficult to remove completely, and ultimately toxic to biological systems. In this work, we present the synthesis of carbohydrate-grafted glycopolymers utilizing a mild and catalyst-free perfluorophenyl azide (PFPA)-mediated Staudinger reaction. Using this strategy, mannose (Man) and maltoheptaose (MH) were grafted onto the biodegradable poly(lactic acid) (PLA) by stirring a PFAA-functionalized PLA with a phosphine-derivatized Man or MH in DMSO at room temperature within an hour. The glycopolymers were characterized by ¹H-NMR, ¹⁹F-NMR, ³¹P-NMR and FTIR. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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17 pages, 5805 KiB

Open AccessArticle

Purification and Glutaraldehyde Activation Study on HCl-Doped PVA–PANI Copolymers with Different Aniline Concentrations

by Jorge M. Guerrero, Amanda Carrillo, María L. Mota, Roberto C. Ambrosio and Francisco S. Aguirre

Molecules 2019, 24(1), 63; https://doi.org/10.3390/molecules24010063 - 25 Dec 2018

Cited by 17 | Viewed by 5417

Abstract

In this work, we report the synthesis and purification of polyvinyl alcohol-polyaniline (PVA–PANI) copolymers at different aniline concentrations, and their molecular (¹H-NMR and FTIR), thermal (TGA/DTG/DSC), optical (UV–Vis-NIR), and microstructural (XRD and SEM) properties before and after activation with glutaraldehyde (GA) [...] Read more.

In this work, we report the synthesis and purification of polyvinyl alcohol-polyaniline (PVA–PANI) copolymers at different aniline concentrations, and their molecular (¹H-NMR and FTIR), thermal (TGA/DTG/DSC), optical (UV–Vis-NIR), and microstructural (XRD and SEM) properties before and after activation with glutaraldehyde (GA) in order to obtain an active membrane. The PVA–PANI copolymers were synthesized by chemical oxidation of aniline using ammonium persulfate (APS) in an acidified (HCl) polyvinyl alcohol matrix. The obtained copolymers were purified by dialysis and the precipitation–redispersion method in order to eliminate undesired products and compare changes due to purification. PVA–PANI products were analyzed as gels, colloidal dispersions, and thin films. ¹H-NMR confirmed the molecular structure of PVA–PANI as the proposed skeletal formula, and FTIR of the obtained purified gels showed the characteristic functional groups of PVA gels with PANI nanoparticles. After exposing the material to a GA solution, the presence of the FTIR absorption bands at 1595 cm⁻¹, 1650 cm⁻¹, and 1717 cm⁻¹ confirmed the activation of the material. FTIR and UV–Vis-NIR characterization showed an increase of the benzenoid section of PANI with GA exposure, which can be interpreted as a reduction of the polymer with the time of activation and concentration of the solution. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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10 pages, 2812 KiB

Open AccessArticle

VE-Albumin Core-Shell Nanoparticles for Paclitaxel Delivery to Treat MDR Breast Cancer

by Bo Tang, Yu Qian, Yi Gou, Gang Cheng and Guihua Fang

Molecules 2018, 23(11), 2760; https://doi.org/10.3390/molecules23112760 - 25 Oct 2018

Cited by 27 | Viewed by 4868

Abstract

Multi-drug resistance (MDR) presents a serious problem in cancer chemotherapy. In this study, Vitamin E (VE)-Albumin core-shell nanoparticles were developed for paclitaxel (PTX) delivery to improve the chemotherapy efficacy in an MDR breast cancer model. The PTX-loaded VE-Albumin core-shell nanoparticles (PTX-VE NPs) had [...] Read more.

Multi-drug resistance (MDR) presents a serious problem in cancer chemotherapy. In this study, Vitamin E (VE)-Albumin core-shell nanoparticles were developed for paclitaxel (PTX) delivery to improve the chemotherapy efficacy in an MDR breast cancer model. The PTX-loaded VE-Albumin core-shell nanoparticles (PTX-VE NPs) had small particle sizes (about 100 nm), high drug entrapment efficiency (95.7%) and loading capacity (12.5%), and showed sustained release profiles, in vitro. Docking studies indicated that the hydrophobic interaction and hydrogen bonds play a significant role in the formation of the PTX-VE NPs. The results of confocal laser scanning microscopy analysis demonstrated that the cell uptake of PTX was significantly increased by the PTX-VE NPs, compared with the NPs without VE (PTX NPs). The PTX-VE NPs also exhibited stronger cytotoxicity, compared with PTX NPs with an increased accumulation of PTX in the MCF-7/ADR cells. Importantly, the PTX-VE NPs showed a higher anti-cancer efficacy in MCF-7/ADR tumor xenograft model than the PTX NPs and the PTX solutions. Overall, the VE-Albumin core-shell nanoparticles could be a promising nanocarrier for PTX delivery to improve the chemotherapeutic efficacy of MDR cancer. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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12 pages, 2811 KiB

Open AccessFeature PaperArticle

Immobilizing Polyether Imidazole Ionic Liquids on ZSM-5 Zeolite for the Catalytic Synthesis of Propylene Carbonate from Carbon Dioxide

by Liying Guo, Xianchao Jin, Xin Wang, Longzhu Yin, Yirong Wang and Ying-Wei Yang

Molecules 2018, 23(10), 2710; https://doi.org/10.3390/molecules23102710 - 21 Oct 2018

Cited by 18 | Viewed by 5617

Abstract

Traditional ionic liquids (ILs) catalysts suffer from the difficulty of product purification and can only be used in homogeneous catalytic systems. In this work, by reacting ILs with co-catalyst (ZnBr₂), we successfully converted three polyether imidazole ionic liquids (PIILs), i.e., HO-[Poly-epichlorohydrin-methimidazole]Cl [...] Read more.

Traditional ionic liquids (ILs) catalysts suffer from the difficulty of product purification and can only be used in homogeneous catalytic systems. In this work, by reacting ILs with co-catalyst (ZnBr₂), we successfully converted three polyether imidazole ionic liquids (PIILs), i.e., HO-[Poly-epichlorohydrin-methimidazole]Cl (HO-[PECH-MIM]Cl), HOOC-[Poly-epichlorohydrin-methimidazole]Cl (HOOC-[PECH-MIM]Cl), and H₂N-[Poly-epichlorohydrin-methimidazole]Cl (H₂N-[PECH-MIM]Cl), to three composite PIIL materials, which were further immobilized on ZSM-5 zeolite by chemical bonding to result in three immobilized catalysts, namely ZSM-5-HO-[PECH-MIM]Cl/[ZnBr₂], ZSM-5-HOOC-[PECH-MIM]Cl/[ZnBr₂], and ZSM-5-H₂N-[PECH-MIM]Cl/[ZnBr₂]. Their structures, thermal stabilities, and morphologies were fully characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The amount of composite PIIL immobilized on ZSM-5 was determined by elemental analysis. Catalytic performance of the immobilized catalysts was evaluated through the catalytic synthesis of propylene carbonate (PC) from CO₂ and propylene oxide (PO). Influences of reaction temperature, time, and pressure on catalytic performance were investigated through the orthogonal test, and the effect of catalyst circulation was also studied. Under an optimal reaction condition (130 °C, 2.5 MPa, 0.75 h), the composite catalyst, ZSM-5-HOOC- [PECH-MIM]Cl/[ZnBr₂], exhibited the best catalytic activity with a conversion rate of 98.3% and selectivity of 97.4%. Significantly, the immobilized catalyst could still maintain high heterogeneous catalytic activity even after being reused for eight cycles. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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9 pages, 1911 KiB

Open AccessArticle

Ultrasensitive (Co)polymers Based on Poly(methacrylamide) Structure with Fining-Tunable pH Responsive Value

by Haiming Fan, Po Li, Wei Li, Hui Li and Xiaonan Huang

Molecules 2018, 23(8), 1870; https://doi.org/10.3390/molecules23081870 - 27 Jul 2018

Cited by 5 | Viewed by 4248

Abstract

Novel pH responsive copolymers with tertiary amine groups were prepared by free radical polymerization with 2-(dialkylamino)ethyl methacrylate monomers. These polymers were pH sensitive with the ability to be responsively fine-tuned in aqueous solution, which was proven through titration, transmittance measurements, and proton nuclear [...] Read more.

Novel pH responsive copolymers with tertiary amine groups were prepared by free radical polymerization with 2-(dialkylamino)ethyl methacrylate monomers. These polymers were pH sensitive with the ability to be responsively fine-tuned in aqueous solution, which was proven through titration, transmittance measurements, and proton nuclear magnetic resonance spectroscopy. The polymers were soluble in water at low pH values, induced by electrostatic repulsion between amine groups, and aggregated above their pK_a value due to the hydrophobic effect of the alkyls. The pH responsive values were precisely tuned from 7.4 to 4.8 by increasing the hydrophobic monomer ratio. Our work provides a novel approach for the development of ultrasensitive pH-responsive polymers for application in biomedical materials. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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11 pages, 1997 KiB

Open AccessArticle

Effect of Hydrophobic Polypeptide Length on Performances of Thermo-Sensitive Hydrogels

by Jiandong Han, Xingyu Zhao, Weiguo Xu, Wei Wang, Yuping Han and Xiangru Feng

Molecules 2018, 23(5), 1017; https://doi.org/10.3390/molecules23051017 - 26 Apr 2018

Cited by 8 | Viewed by 4247

Abstract

Thermosensitive gels are commonly used as drug carriers in medical fields, mainly due to their convenient processing and easy functionalization. However, their overall performance has been severely affected by their unsatisfying biocompatibility and biodegradability. To this end, we synthesized poly(l-alanine) (PLAla)-based [...] Read more.

Thermosensitive gels are commonly used as drug carriers in medical fields, mainly due to their convenient processing and easy functionalization. However, their overall performance has been severely affected by their unsatisfying biocompatibility and biodegradability. To this end, we synthesized poly(l-alanine) (PLAla)-based thermosensitive hydrogels with different degrees of polymerization by ring-opening polymerization. The obtained mPEG₄₅−PLAla copolymers showed distinct transition temperatures and degradation abilities. It was found that slight changes in the length of hydrophobic side groups had a decisive effect on the gelation behavior of the polypeptide hydrogel. Longer hydrophobic ends led to a lower gelation temperature of gel at the same concentration, which implied better gelation capability. The hydrogels showed rapid gelling, enhanced biocompatibility, and better degradability. Therefore, this thermosensitive hydrogel is a promising material for biomedical application. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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Review

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21 pages, 7009 KiB

Open AccessReview

Recent Advances in Phenylboronic Acid-Based Gels with Potential for Self-Regulated Drug Delivery

by Chenyu Wang, Bozhong Lin, Haopeng Zhu, Fei Bi, Shanshan Xiao, Liyan Wang, Guangqing Gai and Li Zhao

Molecules 2019, 24(6), 1089; https://doi.org/10.3390/molecules24061089 - 19 Mar 2019

Cited by 37 | Viewed by 6561

Abstract

Glucose-sensitive drug platforms are highly attractive in the field of self-regulated drug delivery. Drug carriers based on boronic acid (BA), especially phenylboronic acid (PBA), have been designed for glucose-sensitive self-regulated insulin delivery. The PBA-functionalized gels have attracted more interest in recent years. The [...] Read more.

Glucose-sensitive drug platforms are highly attractive in the field of self-regulated drug delivery. Drug carriers based on boronic acid (BA), especially phenylboronic acid (PBA), have been designed for glucose-sensitive self-regulated insulin delivery. The PBA-functionalized gels have attracted more interest in recent years. The cross-linked three-dimensional (3D) structure endows the glucose-sensitive gels with great physicochemical properties. The PBA-based platforms with cross-linked structures have found promising applications in self-regulated drug delivery systems. This article summarizes some recent attempts at the developments of PBA-mediated glucose-sensitive gels for self-regulated drug delivery. The PBA-based glucose-sensitive gels, including hydrogels, microgels, and nanogels, are expected to significantly promote the development of smart self-regulated drug delivery systems for diabetes therapy. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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32 pages, 2082 KiB

Open AccessReview

Polymeric Co-Delivery Systems in Cancer Treatment: An Overview on Component Drugs’ Dosage Ratio Effect

by Jiayi Pan, Kobra Rostamizadeh, Nina Filipczak and Vladimir P. Torchilin

Molecules 2019, 24(6), 1035; https://doi.org/10.3390/molecules24061035 - 15 Mar 2019

Cited by 75 | Viewed by 6871

Abstract

Multiple factors are involved in the development of cancers and their effects on survival rate. Many are related to chemo-resistance of tumor cells. Thus, treatment with a single therapeutic agent is often inadequate for successful cancer therapy. Ideally, combination therapy inhibits tumor growth [...] Read more.

Multiple factors are involved in the development of cancers and their effects on survival rate. Many are related to chemo-resistance of tumor cells. Thus, treatment with a single therapeutic agent is often inadequate for successful cancer therapy. Ideally, combination therapy inhibits tumor growth through multiple pathways by enhancing the performance of each individual therapy, often resulting in a synergistic effect. Polymeric nanoparticles prepared from block co-polymers have been a popular platform for co-delivery of combinations of drugs associated with the multiple functional compartments within such nanoparticles. Various polymeric nanoparticles have been applied to achieve enhanced therapeutic efficacy in cancer therapy. However, reported drug ratios used in such systems often vary widely. Thus, the same combination of drugs may result in very different therapeutic outcomes. In this review, we investigated polymeric co-delivery systems used in cancer treatment and the drug combinations used in these systems for synergistic anti-cancer effect. Development of polymeric co-delivery systems for a maximized therapeutic effect requires a deeper understanding of the optimal ratio among therapeutic agents and the natural heterogenicity of tumors. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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18 pages, 2477 KiB

Open AccessReview

Hydrogels and Their Applications in Targeted Drug Delivery

by Radhika Narayanaswamy and Vladimir P. Torchilin

Molecules 2019, 24(3), 603; https://doi.org/10.3390/molecules24030603 - 8 Feb 2019

Cited by 499 | Viewed by 22922

Abstract

Conventional drug delivery approaches are plagued by issues pertaining to systemic toxicity and repeated dosing. Hydrogels offer convenient drug delivery vehicles to ensure these disadvantages are minimized and the therapeutic benefits from the drug are optimized. With exquisitely tunable physical properties that confer [...] Read more.

Conventional drug delivery approaches are plagued by issues pertaining to systemic toxicity and repeated dosing. Hydrogels offer convenient drug delivery vehicles to ensure these disadvantages are minimized and the therapeutic benefits from the drug are optimized. With exquisitely tunable physical properties that confer them great controlled drug release features and the merits they offer for labile drug protection from degradation, hydrogels emerge as very efficient drug delivery systems. The versatility and diversity of the hydrogels extend their applications beyond targeted drug delivery also to wound dressings, contact lenses and tissue engineering to name but a few. They are 90% water, and highly porous to accommodate drugs for delivery and facilitate controlled release. Herein we discuss hydrogels and how they could be manipulated for targeted drug delivery applications. Suitable examples from the literature are provided that support the recent advancements of hydrogels in targeted drug delivery in diverse disease areas and how they could be suitably modified in very different ways for achieving significant impact in targeted drug delivery. With their enormous amenability to modification, hydrogels serve as promising delivery vehicles of therapeutic molecules in several disease conditions, including cancer and diabetes. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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24 pages, 6520 KiB

Open AccessReview

Recent Development of pH-Responsive Polymers for Cancer Nanomedicine

by Houliang Tang, Weilong Zhao, Jinming Yu, Yang Li and Chao Zhao

Molecules 2019, 24(1), 4; https://doi.org/10.3390/molecules24010004 - 20 Dec 2018

Cited by 164 | Viewed by 11922

Abstract

Cancer remains a leading cause of death worldwide with more than 10 million new cases every year. Tumor-targeted nanomedicines have shown substantial improvements of the therapeutic index of anticancer agents, addressing the deficiencies of conventional chemotherapy, and have had a tremendous growth over [...] Read more.

Cancer remains a leading cause of death worldwide with more than 10 million new cases every year. Tumor-targeted nanomedicines have shown substantial improvements of the therapeutic index of anticancer agents, addressing the deficiencies of conventional chemotherapy, and have had a tremendous growth over past several decades. Due to the pathophysiological characteristics that almost all tumor tissues have lower pH in comparison to normal healthy tissues, among various tumor-targeted nanomaterials, pH-responsive polymeric materials have been one of the most prevalent approaches for cancer diagnosis and treatment. In this review, we summarized the types of pH-responsive polymers, describing their chemical structures and pH-response mechanisms; we illustrated the structure-property relationships of pH-responsive polymers and introduced the approaches to regulating their pH-responsive behaviors; we also highlighted the most representative applications of pH-responsive polymers in cancer imaging and therapy. This review article aims to provide general guidelines for the rational design of more effective pH-responsive nanomaterials for cancer diagnosis and treatment. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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16 pages, 5920 KiB

Open AccessReview

A Perspective on Reversibility in Controlled Polymerization Systems: Recent Progress and New Opportunities

by Houliang Tang, Yi Luan, Lu Yang and Hao Sun

Molecules 2018, 23(11), 2870; https://doi.org/10.3390/molecules23112870 - 3 Nov 2018

Cited by 16 | Viewed by 5668

Abstract

The field of controlled polymerization is growing and evolving at unprecedented rates, facilitating polymer scientists to engineer the structure and property of polymer materials for a variety of applications. However, the lack of degradability, particularly in vinyl polymers, is a general concern not [...] Read more.

The field of controlled polymerization is growing and evolving at unprecedented rates, facilitating polymer scientists to engineer the structure and property of polymer materials for a variety of applications. However, the lack of degradability, particularly in vinyl polymers, is a general concern not only for environmental sustainability, but also for biomedical applications. In recent years, there has been a significant effort to develop reversible polymerization approaches in those well-established controlled polymerization systems. Reversible polymerization typically involves two steps, including (i) forward polymerization, which converts small monomers into macromolecule; and (ii) depolymerization, which is capable of regenerating original monomers. Furthermore, recycled monomers can be repolymerized into new polymers. In this perspective, we highlight recent developments of reversible polymerization in those controlled polymerization systems and offer insight into the promise and utility of reversible polymerization systems. More importantly, the current challenges and future directions to solve those problems are discussed. We hope this perspective can serve as an “initiator” to promote continuing innovations in this fairly new area. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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24 pages, 11121 KiB

Open AccessReview

Smart and Functional Conducting Polymers: Application to Electrorheological Fluids

by Qi Lu, Wen Jiao Han and Hyoung Jin Choi

Molecules 2018, 23(11), 2854; https://doi.org/10.3390/molecules23112854 - 2 Nov 2018

Cited by 42 | Viewed by 6568

Abstract

Electro-responsive smart electrorheological (ER) fluids consist of electrically polarizing organic or inorganic particles and insulating oils in general. In this study, we focus on various conducting polymers of polyaniline and its derivatives and copolymers, along with polypyrrole and poly(ionic liquid), which are adopted [...] Read more.

Electro-responsive smart electrorheological (ER) fluids consist of electrically polarizing organic or inorganic particles and insulating oils in general. In this study, we focus on various conducting polymers of polyaniline and its derivatives and copolymers, along with polypyrrole and poly(ionic liquid), which are adopted as smart and functional materials in ER fluids. Their ER characteristics, including viscoelastic behaviors of shear stress, yield stress, and dynamic moduli, and dielectric properties are expounded and appraised using polarizability measurement, flow curve testing, inductance-capacitance-resistance meter testing, and several rheological equations of state. Furthermore, their potential industrial applications are also covered. Full article

(This article belongs to the Special Issue Smart and Functional Polymers)

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