Supramolecular Hydrogels with Chiral Nanofibril Structures Formed from β-Cyclodextrin and a Rosin-Based Amino Acid Surfactant

QbD Assisted Systematic Review for Optimizing the Selection of PVP as a Ternary Substance in Enhancing the Complexation Efficiency of Cyclodextrins: a Pilot Study

Inclusion complexes require higher concentration of Beta cyclodextrins (βCD) resulting in increased formulation bulk, toxicity, and production costs. This systematic review offers a comprehensive analysis using Quality by design (QbD) as a tool to predict potential applications of Polyvinylpyrrolidone (PVP) as a ternary substance to address issues of inclusion complexes. We reviewed 623 documents from 2013 to 2023 and Eighteen (18) research papers were selected for statistical and meta-analysis using the QbD concept to identify the most critical factors for selecting drugs and effect of PVP on inclusion complexes. The QbD analysis revealed that Molecular weight (MW), Partition coefficient (Log P), and the auxiliary substance ratio directly affected complexation efficiency (CE), thermodynamic stability in terms of Gibbs free energy (ΔG), and percent drug release. However, Stability constant (Ks) remained unaffected by any of these parameters. The results showed that low MW (250), median Log P (6), and a βCD: PVP ratio of 2:3 would result in higher CE, lower G, and improved drug release. PVP improves drug solubility, enhances delivery and therapeutic outcomes, and counteracts increased drug ionization due to decreased pH. In certain cases, its bulky nature and hydrogen bonding with CD molecules can form non-inclusion complexes. The findings of the study shows that there is potential molecular interaction between PVP and β-cyclodextrins, which possibly enhances the stability of inclusion complexes for drug with low MW and log P values less than 9. The systematic review shows a comprehensive methodology based on QbD offers a replicable template for future investigations into drug formulation research.

Ecofriendly Controlled-Release Insecticide Carrier: pH-/Temperature-Responsive Rosin-Derived Hydrogels for Avermectin Delivery against Mythimna separata (Walker)

The exploration of environmentally friendly, less toxic, sustained-release insecticide is increasing with the growing demand for food to meet the requirements of the expanding population. As a sustained-release carrier, the unique, environmentally friendly intelligent responsive hydrogel system is an important factor in improving the efficiency of insecticide utilization and accurate release. In this study, we developed a facile approach for incorporating the natural compound rosin (dehydroabietic acid, DA) and zinc ions (Zn2+) into a poly(N-isopropylacrylamide) (PNIPAM) hydrogel network to construct a controlled-release hydrogel carrier (DA-PNIPAM-Zn2+). Then, the model insecticide avermectin (AVM) was encapsulated in the carrier at a drug loading rate of 36.32% to form AVM@DA-PNIPAM-Zn2+. Surprisingly, the smart controlled carrier exhibited environmental responsiveness, strongly enhanced mechanical properties, self-healing ability, hydrophobicity, and photostability to ensure a balance between environmental friendliness and the precision of the drug release. The release experiments showed that the carboxyl and amide groups in the polymer chains alter the intermolecular forces within the hydrogel meshes and ingredient diffusion by changing temperatures (25 and 40 °C) and pH values (5.8, 7.4, and 8.5), leading to different release behaviors. The insecticidal activity of the AVM@DA-PNIPAM-Zn2+ against oriental armyworms was good, with an effective minimum toxicity toward aquatic animals. Therefore, AVM@DA-PNIPAM-Zn2+ is an effective drug delivery system against oriental armyworms. We anticipate that this ecofriendly, sustainable, smart-response carrier may broaden the utilization rosin and its possible applications in the agricultural sector.

Ecofriendly Viscoelastic Solutions Formed from a Recyclable Rosin-Based Amine Oxide Surfactant

Innovations in molecular structures formed using bioresources are efficient means to prepare surfactant aggregates with unique properties. Here, a rosin-based amine oxide surfactant (R-11-3-AO) containing large hydrophobic groups was synthesized from rosin derivatives, namely, dehydroabietic acid and long-chain amino acids. Cryo-transmission electron microscopy showed that R-11-3-AO molecules formed extremely long wormlike micelles with a cross-sectional diameter of 4-5 nm at a concentration of approximately 7 mmol·L^-1. A gel-like system was obtained at approximately 30 mmol·L^-1 due to the dense entanglement of the wormlike micelles. The solutions also exhibited unique shear thickening behavior at a shear rate of approximately 10 s^-1 even at high concentrations. The large hydrophobic group contained in R-11-3-AO is the origin of the strong van der Waals interactions between the surfactant molecules, resulting in the rapid growth of wormlike micelles. This rosin-based surfactant is the first recoverable amine oxide surfactant from solutions through the salting-out effect with high recovery rates. This work demonstrates the unique capabilities of rosin-based surfactants for forming wormlike micelles and provides opportunities for the development of surfactant recovery technologies.

Rheological behavior of thread-like fiber solutions formed from a rosin-based surfactant with two head groups

Wormlike micelles are conventional aggregates that exist in viscoelastic solutions. However, to achieve a solution with prominent viscoelasticity, rather high concentrations of surfactants are usually required due to the flexibility of aggregates in solution. If thread-like aggregates with rigidity can be formed by surfactants, the solutions are expected to show strong viscoelasticity at very low surfactant concentrations. Herein, A novel rosin-based quaternary ammonium surfactant with two head groups (abbreviated as R-11-3-DA) was synthesized. Cryogenic transmission electron microscopy (Cryo-TEM) images showed that flexible nanofibers with diameters of about 7-8 nm and lengths of over 1 μm were formed in the 1 : 1.5 R-11-3-DA : SL solutions. The rigidity of the aggregates seems to be inherited from the rigidity of the surfactant molecules. The novel aggregates endow the solutions with remarkable viscoelasticity at very low concentrations, with a critical overlap concentration of 0.01 wt% and a critical gelling concentration of 0.58 wt%. The rheological behavior of the solutions also shows excellent shear resistance and weak sensitivity to temperature below the critical gelation temperature (T_gel). This work reveals the advantages of viscoelastic solutions containing flexible nanofibers. The design principles of new molecular structures and system compositions can be applied to the preparation of smart soft materials based on the self-assembly of molecules.

Water-in-Oil Emulsion Gels Stabilized by a Low-Molecular Weight Organogelator Derived from Dehydroabietic Acid

High concentrations of surfactants or gelators are usually necessary to prepare emulsions gels with unusual physicochemical properties. This situation may be improved by innovating the aggregate morphology in systems. Herein, a rosin-based molecule is designed and synthesized using dehydroabietic acid as the starting material (denoted as R-Lys-R). The molecule acts as an effective organogelator and can gelate several hydrocarbon compounds with a minimum gelation concentration of 0.2% (w/v). Analysis using atomic force microscopy (AFM) and circular dichroism (CD) reveals that in n-decane, R-Lys-R forms left-handed helical fibers with a cross-sectional diameter of approximately 15 nm. The directional hydrogen bonding of the amide group is helpful to the formation of aggregates. At concentrations of R-Lys-R above 2%, water-in-oil emulsions are transformed into emulsion gels owing to the aptitude of R-Lys-R in gelating the oil phase. The concentrations of the emulsifier can be adjusted to obtain emulsion gels with different formulations. This work reveals the potential of rosin derivatives for the formation of small molecular weight organogels and provides a novel method for the utilization of natural resources in soft materials and home care products.

Novel Temperature-Responsive Rosin-Derived Supramolecular Hydrogels Constructed by New Semicircular Aggregates

A highly water-soluble rosin-based surfactant (C₁₄-MPA-Na) was synthesized. Novel temperature-responsive supramolecular hydrogels were further prepared using C₁₄-MPA-Na. The microstructure and the mechanical properties of the hydrogels were investigated. Unexpectedly, instead of the long one-dimensional structure, a new kind of twisted semicircular aggregate was formed in the hydrogels, which was rarely reported. Besides, the hydrogels possessed excellent shear-recovery properties. Upon heating to 40 °C, the hydrogels transformed into viscoelastic solutions, which were constructed by worm-like micelles. By adjusting the temperature, the hydrogels and the viscoelastic solutions could be freely transformed. Nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy were used to further explore the possible self-assembly mechanism of C₁₄-MPA-Na. The curved alkane chain which partially overlapped with rosin's rigid skeleton became stretched when heated to 40 °C. The introduction of the rosin rigid skeleton endowed the supramolecular hydrogels with a novel microstructure and contributed to the development of strategies for the utilization of forest resources.

Chiral graphene-based supramolecular hydrogels toward tumor therapy

Drugs with chiral property are playing very important role on precise treatment of diseases (especially antitumor drugs), however, enantioselective delivery of chiral anticancer drugs is still challenge. Herein, a chiral...

Chiral Quaternary Ammoniums Derived from Dehydroabietylamine: Synthesis and Application to Alkynylation of Isatin Derivatives Catalyzed by Silver

Abietic acid and its derivatives have broadly been used in fine chemicals and are renewable resources. Its inherent chiral rigid tricyclic phenanthrene skeleton is unique. Its utilities in asymmetric catalysis remain to be explored. A series new amide-type chiral quaternary ammoniums bearing dehydroabietylamine were designed, and prepared by two convenient steps. Acylation of dehydroabietylamine with bromoacetyl chloride afforded amide holding bromoacetyl group in higher yields using triethyl amine as base. Subsequent quaternization reaction gave the desired amide-type chiral quaternary ammoniums. The new chiral quaternary ammoniums can be used as phase-transfer catalyst (PTC) for the transition metal-catalysed alkynylation of isatin derivatives.

Formation of asymmetric belt-like aggregates from a bio-based surfactant derived from dehydroabietic acid

The morphology and physicochemical properties of ordered molecular aggregates are closely related to surfactant molecules. Herein, a rosin-based amine oxide surfactant containing a large hydrophobic group (abbreviated R-10-AO) was synthesized from dehydroabietic acid, which is an important derivative of rosin. Cryogenic transmission electron microscopy (cryo-TEM) images and small-angle X-ray scattering (SAXS) showed that at a concentration of ∼5 mM, R-10-AO molecules formed flexible nanobelts with a thickness of only 2-3 nm. The width of these nanobelts was 50-150 nm and the length was more than 1 μm. The formation of the stable nanobelts arose from the strong van der Waals forces of the bulky hydrophobic portions of R-10-AO in solution, facilitating the stability of the asymmetrical aggregates. Rheological tests showed that the formed nanobelts were thermodynamically stable. The entanglement of these nanobelts led to significant viscoelasticity of the solutions. The zero-shear viscosity (η₀) of the R-10-AO solution reached 10 Pa s at a concentration of 5 mM, which is much greater than that of most wormlike micellar solutions. This work provides the inspirations of preparing aggregates with novel properties using natural products.

Facile Construction of Bio-Based Supramolecular Hydrogels from Dehydroabietic Acid with a Tricyclic Hydrophenanthrene Skeleton and Stabilized Gel Emulsions

Supramolecular hydrogels have attracted great attention due to their special properties. In this research, bio-based supramolecular hydrogels were conveniently constructed by heating and ultrasounding two components of dehydroabietic acid with a rigid tricyclic hydrophenanthrene skeleton and morpholine. The microstructures and properties of hydrogels were investigated by DSC, rheology, SAXS, CD spectroscopy, and cryo-TEM, respectively. The critical gel concentration (CGC) of the hydrogel was 0.3 mol·L⁻¹ and the gel temperature was 115 °C. In addition, the hydrogel showed good stability and mechanical properties according to rheology results. Cryo-TEM images reveal that the microstructure of hydrogel is fibrous meshes; its corresponding mechanism has been studied using FT-IR spectra. Additionally, oil-in-water gel emulsions were prepared by the hydrogel at a concentration above its CGC, and the oil mass fraction of the oil-in-water gel emulsions could be freely adjusted between 5% and 70%. This work provides a convenient way to prepare bio-based supramolecular hydrogels and provides a new method for the application of rosin.

Photoresponsive Viscoelastic Solutions Based on Chiral Wormlike Micelles in Mixed Solutions Containing an Amphiphile Derived from Rosin

A novel rosin-based photoresponsive anionic amphiphile, sodium N-azophenyl maleopimaric acid imide carboxylate (AzoMPCOONa), has been successfully synthesized. Its molecular structure was characterized by ¹H and ¹³C NMR and mass spectrometry (MS). The photoisomerization of AzoMPCOONa was evaluated by ultraviolet (UV)-visible spectrometry and ¹H NMR. The structure of AzoMPCOONa could be converted between the trans and cis isomers by irradiation with UV/visible light. Importantly, a fascinating photoresponsive viscoelastic solution was prepared by mixing AzoMPCOONa and cetyltrimethylammonium bromide (CTAB). The properties of the photoresponsive viscoelastic solution were further investigated by rheology, circular dichroism (CD), and cryogenic transmission electron microscopy (cryo-TEM). Initially, the AzoMPCOONa/CTAB system was a gel-like solution composed of entangled wormlike micelles possessing the right-handed chiral structure. After UV irradiation for 10 min, the gel-like solution transformed into a slightly viscous solution, its zero-shear viscosity dramatically reduced by 2 orders of magnitude, and the aggregates were converted into rod-like micelles and spherical micelles. In addition, the right-handed chiral structure of the aggregates disappeared. These dramatic changes in the viscosity and the aggregate structure can be attributed to the photoisomerization of the azobenzene group in AzoMPCOONa, which led to changes in the molecular geometry and the packing parameter of the AzoMPCOONa/CTAB system. Interestingly, the right-handed chiral structure of wormlike micelles also is photoresponsive. The results reveal the superiority of forest resources for preparing viscoelastic solutions.

Bioinspired organohydrogels with heterostructures: Fabrications, performances, and applications

Since emerging in 1960, the artificial hydrogels have garnered enormous attentions in scientific community due to their high level of similarities to biological soft tissues in both structures and properties. With the proceeding of research, the concern of hydrogels is gradually shifted from fundamental investigation to abundant functionalization. In contrast to the natural soft tissues, the current artificial hydrogels still possess relatively simple structures and unsatisfactory environmental adaptability, extremely limiting their practical applications in complex environments. Enlightened by the prominent adaptability of biological organisms, the binary cooperative complementary principle is utilized to develop bioinspired organohydrogels by combining two components with opposite but cooperative physiochemical features. The present review provides the advanced progresses of bioinspired organohydrogels with sophisticated heterogeneous networks and desirably environmental adaptabilities. We clearly summarize the synthesizing strategies in regard to both corresponding mechanisms and typical examples, including macroscopic organohydrogels, organohydrogels with binary solvent, organohydrogels with heteronetworks, and emulsion-based organohydrogels. Meanwhile, the intriguing features of the reported organohydrogels, such as temperature resistance, switchable mechanics, adaptive wettability, and opposite components compatibility, are also clearly highlighted with a short overview of their promising applications. Ultimately, the current challenges and perspectives on the future development of bioinspired organohydrogels are also discussed.