Polyglycerol-Functionalized β-Cyclodextrins as Crosslinkers in Thermoresponsive Nanogels for the Enhanced Dermal Penetration of Hydrophobic Drugs

Thermoresponsive nanogels (tNGs) are promising candidates for dermal drug delivery. However, poor incorporation of hydrophobic drugs into hydrophilic tNGs limits the therapeutic efficiency. To address this challenge, β-cyclodextrins (β-CD) are functionalized by hyperbranched polyglycerol serving as crosslinkers (hPG-βCD) to fabricate βCD-tNGs. This novel construct exhibits augmented encapsulation of hydrophobic drugs, shows the appropriate thermal response to dermal administration, and enhances the dermal penetration of payloads. The structural influences on the encapsulation capacity of βCD-tNGs for hydrophobic drugs are analyzed, while concurrently retaining their efficacy as skin penetration enhancers. Various synthetic parameters are considered, encompassing the acrylation degree and molecular weight of hPG-βCD, as well as the monomer composition of βCD-tNGs. The outcome reveals that βCD-tNGs substantially enhance the aqueous solubility of Nile Red elevating to 120 µg mL-1 and augmenting its dermal penetration up to 3.33 µg cm-2. Notably, the acrylation degree of hPG-βCD plays a significant role in dermal drug penetration, primarily attributed to the impact on the rigidity and hydrophilicity of βCD-tNGs. Taken together, the introduction of the functionalized β-CD as the crosslinker in tNGs presents a novel avenue to enhance the efficacy of hydrophobic drugs in dermatological applications, thereby offering promising opportunities for boosted therapeutic outcomes.

Hydrophobicity-enhanced ferritin nanoparticles for efficient encapsulation and targeted delivery of hydrophobic drugs to tumor cells

Ferritin, a naturally occurring iron storage protein, has gained significant attention as a drug delivery platform due to its inherent biocompatibility and capacity to encapsulate therapeutic agents. In this study, we successfully genetically engineered human H ferritin by incorporating 4 or 6 tryptophan residues per subunit, strategically oriented towards the inner cavity of the nanoparticle. This modification aimed to enhance the encapsulation of hydrophobic drugs into the ferritin cage. Comprehensive characterization of the mutants revealed that only the variant carrying four tryptophan substitutions per subunit retained the ability to disassemble and reassemble properly. As a proof of concept, we evaluated the loading capacity of this mutant with ellipticine, a natural hydrophobic indole alkaloid with multimodal anticancer activity. Our data demonstrated that this specific mutant exhibited significantly higher efficiency in loading ellipticine compared to human H ferritin. Furthermore, to evaluate the versatility of this hydrophobicity-enhanced ferritin nanoparticle as a drug carrier, we conducted a comparative study by also encapsulating doxorubicin, a commonly used anticancer drug. Subsequently, we tested both ellipticine and doxorubicin-loaded nanoparticles on a promyelocytic leukemia cell line, demonstrating efficient uptake by these cells and resulting in the expected cytotoxic effect.

Promising strategies for improving oral bioavailability of poor water-soluble drugs

INTRODUCTION

Oral administration of poorly water-soluble drugs (PWSDs) is generally related to low bioavailability, leading to high drug doses, multiple side effects, and low patient compliance. Thus, different strategies have been developed to increase drug solubility and dissolution in the gastrointestinal tract, opening new venues for these drugs.

AREAS COVERED

This review outlines the current challenges in PWSD formulation development and the strategies to overcome the oral barriers and increase their solubility and bioavailability. Conventional strategies include altering crystalline and molecular structures and modifying oral solid dosage forms. In contrast, novel strategies comprise micro- and nanostructured systems. Recent representative studies involving how these strategies have improved the oral bioavailability of PWSDs were also reviewed and reported.

EXPERT OPINION

New approaches to enhance PWSD bioavailability have sought to improve water solubility and dissolution rates, drug protection by overcoming biological barriers, and increased absorption. Still, only a handful of studies have focused on quantifying the increase in bioavailability. Improving the oral bioavailability of PWSDs remains an exciting unexplored field of research and has become an important issue for successfully developing pharmaceutical products.

Amphiphilic Polypeptides Obtained by the Post-Polymerization Modification of Poly(Glutamic Acid) and Their Evaluation as Delivery Systems for Hydrophobic Drugs

Synthetic poly(amino acids) are a unique class of macromolecules imitating natural polypeptides and are widely considered as carriers for drug and gene delivery. In this work, we synthesized, characterized and studied the properties of amphiphilic copolymers obtained by the post-polymerization modification of poly(α,L-glutamic acid) with various hydrophobic and basic L-amino acids and D-glucosamine. The resulting glycopolypeptides were capable of forming nanoparticles that exhibited reduced macrophage uptake and were non-toxic to human lung epithelial cells (BEAS-2B). Moreover, the developed nanoparticles were suitable for loading hydrophobic cargo. In particular, paclitaxel nanoformulations had a size of 170-330 nm and demonstrated a high cytostatic efficacy against human lung adenocarcinoma (A549). In general, the obtained nanoparticles were comparable in terms of their characteristics and properties to those based on amphiphilic (glyco)polypeptides obtained by copolymerization methods.

Facile Preparation of Drug-Releasing Supramolecular Hydrogel for Preventing Postoperative Peritoneal Adhesion

Hydrogels have attracted widespread attention for breaking the bottlenecks faced during facile drug delivery. To date, the preparation of jelly carriers for hydrophobic drugs remains challenging. In this study, by evaporating ethanol to drive the formation of hydrogen bonds, hydrophilic poly(vinyl alcohol) (PVA) and certain hydrophobic compounds [luteolin (LUT), quercetin (QUE), and myricetin (MYR)] were rapidly prepared into supramolecular hydrogel within 10 min. The gelation performance of these three hydrogels changed regularly with the changing sequence of LUT, QUE, and MYR. An investigation of the gelation pathway of these hybrid gels reveals that the formation of this type of gel follows a simple supramolecular self-assembly process, called "hydrophobe-hydrophile crosslinked gelation". Because the hydrogen bond between PVA and the drug is noncovalent and reversible, the hydrogel has good plasticity and self-healing properties, while the drugs can be controllably released by tuning the output stimuli. Using a rat sidewall-cecum abrasion adhesion model, the as-prepared hydrogel was highly efficient and safe in preventing postsurgical adhesion. This work provides a useful archetypical template for researchers interested in the efficient delivery and controllable release of hydrophobic drugs.

High-Loading Self-Assembling Peptide Nanoparticles as a Lipid-Free Carrier for Hydrophobic General Anesthetics

Purpose

Typical hydrophobic amino acids (HAAs) are important motifs for self-assembling peptides (SAPs), but they lead to low water-solubility or compact packing of peptides, limiting their capacity for encapsulating hydrophobic drugs. As an alternative, we designed a peptide GQY based on atypical HAAs, which could encapsulate hydrophobic drugs more efficiently. Although hydrophobic general anesthetics (GAs) have been formulated as lipid emulsions, their lipid-free formulations have been pursued because of some side effects inherent to lipids. Using GAs as targets, potential application of GQY as a carrier for hydrophobic drugs was evaluated.

Methods

Thioflavin-T (ThT) binding test, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to examine the self-assembling ability of GQY. Pyrene and 8-Anilino-1-naphthalenesulfonic acid (ANS) were used to confirm formation of hydrophobic domain in GQY nanoparticles. Using pyrene as a model, GQY’s capacity to encapsulate hydrophobic drugs was evaluated. GAs including propofol, etomidate and ET26 were encapsulated by GQY. Loss of righting reflex (LORR) test was conducted to assess the anesthetic efficacy of these lipid-free formulations. Paw-licking test was used to evaluate pain-on-injection of propofol-GQY (PROP-GQY) formulation. Hemolytic and cytotoxicity assay were used to evaluate biocompatibility of GQY.

Results

Stable nanoparticles containing plenty of hydrophobic cavities could be formed by GQY, which could encapsulate hydrophobic drugs at very high concentration and form stable suspensions. Propofol, etomidate and ET26 formulated by GQY showed anesthetic efficacy comparable to their currently available formulations. Unlike clinic lipid emulsion, PROP-GQY formulation did not cause pain-on-injection in rats. Neither obvious cytotoxicity nor hemolytic activity of GQY was observed.

Conclusion

GQY could encapsulate GAs to obtain stable and effective formulations. As a lipid-free carrier, GQY exhibited considerable biocompatibility and other side benefits such as reducing pain-on-injection. More SAPs based on atypical HAAs could be designed as promising carriers for hydrophobic drugs.

Design and Use of a Thermogelling Methylcellulose Nanoemulsion to Formulate Nanocrystalline Oral Dosage Forms

Oral drug products have become indispensable in modern medicine because of their exceptional patient compliance. However, poor bioavailability of ubiquitous low-water-soluble active pharmaceutical ingredients (APIs) and lack of efficient oral drug formulations remain as significant challenges. Nanocrystalline formulations are an attractive route to increase API solubility, but typically require abrasive mechanical milling and several processing steps to create an oral dosage form. Using the dual amphiphilic and thermoresponsive properties of methylcellulose (MC), a new thermogelling nanoemulsion and a facile thermal dripping method are developed for efficient formulation of composite particles with the MC matrix embedded with precisely controlled API nanocrystals. Moreover, a fast and tunable release performance is achieved with the combination of a fast-eroding MC matrix and fast-dissolving API nanocrystals. Using the versatile thermal processing approach, the thermogelling nanoemulsion is easily formulated into a wide variety of dosage forms (nanoparticle suspension, drug tablet, and oral thin film) in a manner that avoids nanomilling. Overall, the proposed thermogelling nanoemulsion platform not only broadens the applications of thermoresponsive nanoemulsions but also shows great promise for more efficient formulation of oral drug products with high quality and tunable fast release.

Recent advances in polymer shell oily-core nanocapsules for drug-delivery applications

Polymeric nanocapsules are vesicular drug-delivery systems composed of an inner oily reservoir surrounded by polymeric membranes. Nanocapsules have various advantages over other nanovesicular systems such as providing controlled drug release properties. We discuss the recent advances in polymeric shell oily-core nanocapsules, illustrating the different types of polymers used and their implementation. Nanocapsules can be utilized for many purposes, especially encapsulation of highly lipophilic drugs. They have been shown to have variable applications, especially in cancer therapy, due to the ability of the polymeric shell to direct the loaded drugs to their target sites, as well as their high internalization efficacy. Those productive applications guaranteed their high potential as drug-delivery systems. However, their clinical development is still in an early stage.

Preparation and in-vitro evaluation of β-CD/HA nanocomposite as a potential carrier for hydrophobic drugs

This study aimed to provide a new drug delivery system for hydrophobic compounds. Dexamethasone (DEX) was employed as a hydrophobic model drug, which incorporated into the network of hydroxyapatite (HA)/Cyclodextrin (β-CD) nanocomposite. Phase analysis, chemical bonding, morphology, and drug release was evaluated using XRD, FTIR, FESEM, and UV-vis spectroscopy, respectively. XRD patterns showed the formation of the crystalline structure and FTIR analysis showed the chemical bonding between organic and inorganic phases. FESEM images accompanied by EDX analysis confirmed the presence of HA nano-flakes. Release of DEX loaded β-CD/HA was measured to be around 4.6% and 18.7% in pH5.3 and pH 7.4, respectively. In conclusion, the prepared system could be a potential pH sensitive carrier for sustainable release of water-insoluble drugs.

Assessing the pharmacokinetics and toxicology of polymeric micelle conjugated therapeutics

Introduction: Analogous to nanocarriers such as nanoparticles, liposomes, nano lipoidal carriers, niosomes, and ethosomes, polymeric micelles have gained significance in the field of drug delivery. They have attracted scientists worldwide by their nanometric size, wide range of polymers available for building block synthesis, stability and potential to enhance the targeting and safety of drugs. Incorporation of drugs within the interior of polymeric micelles alters the drug pharmacokinetics, which generally results in increased efficiency.Areas covered: This review deals with the pharmacokinetics of various anti-neoplastic drugs loaded into micelles. The structure of polymeric micelles, polymers employed in their development and techniques involved will be discussed. This is followed by discussion on the pharmacokinetics of anti-cancer drugs loaded into polymeric micelles and the toxicity concerns associated.Expert opinion: Polymeric micelles are nanometeric carriers, with higher stability, polymeric flexibility and higher drug loading of poorly water-soluble drugs. These nanosystems help in increasing the bioavailability of drugs by encapsulating them within the hydrophobic core. The proper selection and design of the amphiphilic polymer for micelles is a crucial step as it decides the toxicity and the biocompatibility.

Photo-Responsive Polymersomes as Drug Delivery System for Potential Medical Applications

Due to a strong retardation effect of o-nitrobenzyl ester on polymerization, it is still a great challenge to prepare amphiphilic block copolymers for polymersomes with a o-nitrobenzyl ester-based hydrophobic block. Herein, we present one such solution to prepare amphiphilic block copolymers with pure poly (o-nitrobenzyl acrylate) (PNBA) as the hydrophobic block and poly (N,N'-dimethylacrylamide) (PDMA) as the hydrophilic block using bulk reversible addition-fragmentation chain transfer (RAFT) polymerization of o-nitrobenzyl acrylate using a PDMA macro-RAFT agent. The developed amphiphilic block copolymers have a suitable hydrophobic/hydrophilic ratio and can self-assemble into photoresponsive polymersomes for co-loading hydrophobic and hydrophilic cargos into hydrophobic membranes and aqueous compartments of the polymersomes. The polymersomes demonstrate a clear photo-responsive characteristic. Exposure to light irradiation at 365 nm can trigger a photocleavage reaction of o-nitrobenzyl groups, which results in dissociation of the polymersomes with simultaneous co-release of hydrophilic and hydrophobic cargoes on demand. Therefore, these polymersomes have great potential as a smart drug delivery nanocarrier for controllable loading and releasing of hydrophilic and hydrophobic drug molecules. Moreover, taking advantage of the conditional releasing of hydrophilic and hydrophobic drugs, the drug delivery system has potential use in medical applications such as cancer therapy.

Think Beyond the Core: Impact of the Hydrophilic Corona on Drug Solubilization Using Polymer Micelles

Polymeric micelles are typically characterized as core-shell structures. The hydrophobic core is considered as a depot for hydrophobic molecules, and the corona-forming block acts as a stabilizing and solubilizing interface between the core and aqueous milieu. Tremendous efforts have been made to tune the hydrophobic block to increase the drug loading and stability of micelles, whereas the role of hydrophilic blocks is rarely investigated in this context, with poly(ethylene glycol) (PEG) being the gold standard of hydrophilic polymers. To better understand the role of the hydrophilic corona, a small library of structurally similar A-B-A-type amphiphiles based on poly(2-oxazoline)s and poly(2-oxazine)s is investigated by varying the hydrophilic block A utilizing poly(2-methyl-2-oxazoline) (pMeOx; A) or poly(2-ethyl-2-oxazoline) (pEtOx; A*). In terms of hydrophilicity, both polymers closely resemble PEG. The more hydrophobic block B bears either a poly(2-oxazoline) and poly(2-oxazine) backbone with C3 (propyl) and C4 (butyl) side chains. Surprisingly, major differences in loading capacities from A-B-A > A*-B-A > A*-B-A* is observed for the formulation with two poorly water-soluble compounds, curcumin and paclitaxel, highlighting the importance of the hydrophilic corona of polymer micelles used for drug formulation. The formulations are also characterized by various nuclear magnetic resonance spectroscopy methods, dynamic light scattering, cryogenic transmission electron microscopy, and (micro) differential scanning calorimetry. Our findings suggest that the interaction between the hydrophilic block and the guest molecule should be considered an important, but previously largely ignored, factor for the rational design of polymeric micelles.

Cell Membrane Camouflaged Hydrophobic Drug Nanoflake Sandwiched with Photosensitizer for Orchestration of Chemo-Photothermal Combination Therapy

Many candidate anticancer drugs have suffered from their intrinsic hydrophobicity, which poses several obstacles for clinical application. To overcome this challenge and further improve the performance, herein a nanocrystal-based biomimetic formulation with a sandwich structure is developed. As the core, flake shaped nanocrystals (NCs) with high loading of the hydrophobic drug hydroxycamptothecin (HCPT) are synthesized via a mild nanoprecipitation process by exploring the template effect of serum albumin. Meanwhile, the camouflaged cancer cell membrane (CM) composed of plentiful membrane proteins endows the NCs with homotypic targeting capacity at tumor sites. In addition, the photosensitizer indocyanine green sandwiched between NCs and CM not only converts near infrared light to heat for photothermal treatment but also improves the dissolution of HCPT NCs for chemotherapy. These features corporately achieve the orchestration of chemo-photothermal combination therapy and completely inhibit tumor growth with few adverse effects, showing promise as a new modality for the utilization of hydrophobic drugs to treat cancer.

Photopolymerized Micelle-Laden Hydrogels Can Simultaneously Form and Encapsulate Nanocrystals to Improve Drug Substance Solubility and Expedite Drug Product Design

Formulation technologies are critical for increasing the efficacy of drug products containing poorly soluble hydrophobic drugs, which compose roughly 70% of small molecules in commercial pipelines. Nanomedicines, such as nanocrystal formulations and amorphous solid suspensions, are effective approaches to increasing solubility. However, existing techniques require additional processing into a final dosage form, which strongly influences drug delivery and clinical performance. To enhance hydrophobic drug product efficacy and clinical throughput, a hydrogel material is developed as a sacrificial template to simultaneously form and encapsulate nanocrystals. These hydrogels contain micelles chemically bound to the hydrogel matrix, where the surfactant structure dictates the crystal size and drug loading. Therefore, nanocrystals can be produced in high yield (up to 90% drug loading, by weight) with precisely controlled sizes as small as 4 nm independently of hydrogel composition. Nanocrystals and surfactant are then released together to increase the solubility up to 70 times above bulk crystalline material. By integrating nanocrystals into a final dosage form, micelle-laden hydrogels simplify hydrophobic drug product design.

Long-Circulating Hyaluronan-Based Nanohydrogels as Carriers of Hydrophobic Drugs

Nanohydrogels based on natural polymers, such as polysaccharides, are gaining interest as vehicles for therapeutic agents, as they can modify the pharmacokinetics and pharmacodynamics of the carried drugs. In this work, hyaluronan-riboflavin nanohydrogels were tested in vivo in healthy rats highlighting their lack of toxicity, even at high doses, and their different biodistribution with respect to that of native hyaluronan. They were also exploited as carriers of a hydrophobic model drug, the anti-inflammatory piroxicam, that was physically embedded within the nanohydrogels by an autoclave treatment. The nanoformulation was tested by intravenous administration showing an improvement of the pharmacokinetic parameters of the molecule. The obtained results indicate that hyaluronan-based self-assembled nanohydrogels are suitable systems for low-soluble drug administration, by increasing the dose as well as the circulation time of poorly available therapeutic agents.

Itraconazole encapsulated PLGA-nanoparticles covered with mannose as potential candidates against leishmaniasis

Leishmaniasis is a neglected disease threatening over 350 million people. Antimonials are first-line drugs due to resistance and side effects there is a demand for alternative chemotherapy. Itraconazole (ITZ) is an antimycotic. It was encapsulated into poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) and covered with mannose. The NPs were 250 nm and -1.1 mV ± 0.7. PLGA-ITZ-mannose NPs presented a toxicity of 20.7% for J774 cells, and no toxicity for THP 1. The J774 cells were infected with three Leishmania promastigotes strains and treated with ITZ loaded PLGA NPs with/without mannose. The parasite percentage of L.(V.) panamensis intracellular amastigotes significantly (p < 0.01) decreased from 34.4% to 13.7% and 5.7% for PLGA-ITZ-mannose NPs and PLGA-ITZ NPs, respectively. For L.(L.) infantum there was a reduction (p < 0.001) from 18.1% to 4.8% and 8.3% for PLGA-ITZ-mannose NPs and PLGA-ITZ NPs, respectively. Further with L.(L.) braziliensis amastigotes there was a significant reduction (p < 0.001) from 54.9% to 28% and 21.1% for PLGA-ITZ-mannose NPs and PLGA-ITZ NPs, respectively. Adding mannose increased the efficacy PLGA-ITZ NPs against L.(L.) infantum, while it had no effect against L(V.) panamensis and L.(L.) braziliensis amastigotes. We recommend further investigation of PLGA-ITZ-mannose NPs in animal models to evaluate their potential. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 00B: 000-000, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 680-687, 2019.

Hydrogels for Hydrophobic Drug Delivery. Classification, Synthesis and Applications

Hydrogels have been shown to be very useful in the field of drug delivery due to their high biocompatibility and ability to sustain delivery. Therefore, the tuning of their properties should be the focus of study to optimise their potential. Hydrogels have been generally limited to the delivery of hydrophilic drugs. However, as many of the new drugs coming to market are hydrophobic in nature, new approaches for integrating hydrophobic drugs into hydrogels should be developed. This article discusses the possible new ways to incorporate hydrophobic drugs within hydrogel structures that have been developed through research. This review describes hydrogel-based systems for hydrophobic compound delivery included in the literature. The section covers all the main types of hydrogels, including physical hydrogels and chemical hydrogels. Additionally, reported applications of these hydrogels are described in the subsequent sections.

Development and tailoring of hybrid lipid nanocarriers

BACKGROUND

Lipid nanoparticles are considered one of the most promising systems for controlled release of therapeutic molecules highly hydrophobic and with low biodisponibility. Solid lipid nanoparticles and nanostructured lipids carriers are widely seen as the workhorses of drug delivery systems because of low toxicity, enhanced encapsulation capacity, controlled drug kinetic release, easy tailoring and targeting and practicable scale up.

CONCLUSIONS

A new generation of hybrid lipid nanoparticles has emerged by combining the lipidic properties with polymers, proteins and metallic structures. The main features of hybrid lipid nanoparticles including popular methods for synthesis and characterization, biological and toxicological properties, administration routes, drug encapsulation strategies, tailoring and targeting, and potential systems for use in biomedicine are described in the present review.

Multicompartment Theranostic Nanoemulsions Stabilized by a Triphilic Semifluorinated Block Copolymer

The presence of a perfluorocarbon block in a multiblock polymer has been shown to be an additional driving force toward nanoparticle assembly. In the preparation of nanoemulsions, this perfluorocarbon block also provides enhanced particle stability. Herein, the synthesis of a new triphilic, semifluorinated copolymer, M2F8H18, is introduced. This ABC type block copolymer can be used to formulate extremely stable nanoemulsions, assembled around a lipophilic droplet, with lifetimes of one year or more. The central oil droplet can stably solubilize high concentrations of hydrophobic drugs, making this system an ideal drug delivery vehicle. The incorporation of the perfluorocarbon block modulates drug release from the lipophilic core via the surrounding fluorous shell. Fluorous imaging agents incorporated into the fluorous shell prolong drug release even further as well as provide potent ¹⁹F-MRI contrast ability. In vitro studies show that these nanoemulsions efficiently inhibit cancer cell growth, thus providing a theranostic drug delivery system.

Preloading of Hydrophobic Anticancer Drug into Multifunctional Nanocarrier for Multimodal Imaging, NIR-Responsive Drug Release, and Synergistic Therapy

Applications of hydrophobic drug-based nanocarriers (NCs) remain largely limited because of their low loading capacity. Here, development of a multifunctional hybrid NC made of a magnetic Fe3O4 core and a mesoporous silica shell embedded with carbon dots (CDs) and paclitaxel (PTX), and covered by another layer of silica is reported. The NC is prepared via a one-pot process under mild condition. The PTX loading method introduced in this study simplifies drug loading process and demonstrates a high loading capacity due to mesoporous silica dual-shell structure, supramolecular π-stacking between conjugated rings of PTX molecules, and aromatic rings of the CDs in the hybrid NC. The CDs serve as both confocal and two-photon fluorescence imaging probes, while the Fe3O4 core serves as a magnetic resonance imaging contrast agent. Significantly, NC releases PTX in response to near infrared irradiation as a result of local heating of the embedded CDs and the heating of CDs also provides an additional therapeutic effect by thermally killing cancer cells in tumor in addition to the chemotherapeutic effect of released PTX. Both in vitro and in vivo results show that NC demonstrates high therapeutic efficacy through a synergistic effect from the combined chemo-photothermal treatments.

Hydrogels with smart systems for delivery of hydrophobic drugs

INTRODUCTION

Smart hydrogel systems present opportunities to not only provide hydrophobic molecule encapsulation capability but to also respond to specific delivery routes. Areas covered: An overview of the design principles, preparation methods and applications of hydrogel systems for delivery of hydrophobic drugs is given. It begins with a summary of the advantages of hydrogels as delivery vehicles over other approaches, particularly macromolecular nanocarriers, before proceeding to address the design and preparation strategies and chemistry involved, with a particular focus on the introduction of hydrophobic domains into (naturally) hydrophilic hydrogels. Finally, the applications in different delivery routes are discussed. Expert opinion: Modifications to conventional hydrogels can endow them with the capability to carry hydrophobic drugs but other functions as well, such as the improved mechanical stability, which is important for long-term in vivo residence and/or self-healing properties useful for injectable delivery pathways. These modifications harness hydrophobic-hydrophobic forces, physical interactions and inclusion complexes. The lack of in-depth understanding of these interactions, currently limits more delicate and application-oriented designs. Increased efforts are needed in (i) understanding the interplay of gel formation and simultaneous drug loading; (ii) improving hydrogel systems with respect to their biosafety; and (iii) control over release mechanism and profile.

Interfacial Cohesion and Assembly of Bioadhesive Molecules for Design of Long-Term Stable Hydrophobic Nanodrugs toward Effective Anticancer Therapy

The majority of anticancer drugs are poorly water-soluble and thus suffer from rather low bioavailability. Although a variety of delivery carriers have been developed for bioavailability improvement, they are severely limited by low drug loading and undesired side effects. The optimum delivery vehicle would be a biocompatible and biodegradable drug nanoparticle of uniform size with a thin but stable shell, making it soluble, preventing aggregation and enabling targeting. Here, we present a general strategy for the rational design of hydrophobic drug nanoparticles with high drug loading by means of interfacial cohesion and supramolecular assembly of bioadhesive species. We demonstrate that the pathway is capable of effectively suppressing and retarding Ostwald ripening, providing drug nanoparticles with small and uniform size and long-term colloidal stability. The final complex drug nanoparticles provide higher tumor accumulation, negligible toxicity, and enhanced antitumor activity, superior to commercial formulations. Our findings demonstrate that local, on-demand coating of hydrophobic nanoparticles is achievable through cooperation and compromise of interfacial adhesion and assembly.

Hydrogel-Based Drug Delivery Systems for Poorly Water-Soluble Drugs

Hydrogels are three-dimensional materials that can withstand a great amount of water incorporation while maintaining integrity. This allows hydrogels to be very unique biomedical materials, especially for drug delivery. Much effort has been made to incorporate hydrophilic molecules in hydrogels in the field of drug delivery, while loading of hydrophobic drugs has not been vastly studied. However, in recent years, research has also been conducted on incorporating hydrophobic molecules within hydrogel matrices for achieving a steady release of drugs to treat various ailments. Here, we summarize the types of hydrogels used as drug delivery vehicles, various methods to incorporate hydrophobic molecules in hydrogel matrices, and the potential therapeutic applications of hydrogels in cancer.

Advances in lipid-based drug delivery: enhancing efficiency for hydrophobic drugs

INTRODUCTION

Many drug candidates with high therapeutic efficacy have low water solubility, which limits the administration and transport across physiological barriers, for example, the tumor tissue barrier. Therefore, strategies are needed to permeabilize the physiological barriers safely so that hydrophobic drugs may be delivered efficiently.

AREAS COVERED

This review focuses on prospects for therapeutic application of lipid-based drug delivery carriers that increase hydrophobic drugs to improve their solubility, bioavailability, drug release, targeting and absorption. Moreover, novel techniques to prepare for lipid-based drug delivery to extend pharmaceuticals with poor bioavailability such as surface modifications of lipid-based drug delivery are presented. Industrial developments of several drug candidates employing these strategies are discussed, as well as applications and clinical trials.

EXPERT OPINION

Overall, hydrophobic drugs can be encapsulated in the lipid-based drug delivery systems, represent a relatively safe and promising strategy to extend drug retention, lengthen the lifetime in the circulation, and allow active targeting to specific tissues and controllable drug release in the desirable sites. However, there are still noticeable gaps that need to be filled before the theoretical advantage of these formulations may truly be realized such as investigation on the use of lipid-based drug delivery for administration routes. This research may provide further interest within the area of lipid-based systems, both in industry and in the clinic.

Improvement in solubility of poor water-soluble drugs by solid dispersion

This article is intended to combine recent literature on solid dispersion technology for solubility enhancement with special emphasis on mechanism responsible for the same by solid dispersion, various preparation methods, and evaluation parameters. Solubility behavior is the most challenging aspect for various new chemical entities as 60% of the new potential products possess solubility problems. This is the biggest reason for new drug molecules not reaching to the market or not reaches to full potential. There are various techniques to enhance the drug solubility such as particle size reduction, nanosuspension, use of surfactants, salt formation, solid dispersion, etc. From this article it may be concluded that solid dispersion is an important approach for improvement of bioavailability of poor water-soluble drugs.