Towards Formulation of Highly Acidic Active Ingredients: Development of Clinically Effective Concentrated Trichloroacetic Acid Gel for Wart Management.

Common warts are benign skin lesions caused by the human papillomavirus. Although they are usually not harmful, they can cause pain, depending on their location. While many modalities are available for treatment of warts, none is a gold standard, and many are not affordable and/or have suboptimal outcomes. Trichloroacetic acid (TCA) is a chemical tissue-destroying agent used as a highly concentrated solution for wart management. While available and efficient, it is difficult to handle as the solution spreads to tissue surrounding the wart causing pain and burning. Hence, we developed a new polymer-based gel of high TCA content (100% w/v). Gels were formed successfully as hydroxyethyl cellulose (HEC) and chitosan were used to impart viscosity and bioadhesion. Formulae of different concentrations were tested for their physical properties, and the optimal formulation was selected for clinical evaluation. A combination of 3% HEC and 2% chitosan provided optimal viscosity and limited water content and have acceptable stability. The efficacy and safety of the biweekly application of TCA gel were evaluated in 30 patients. The clinical study revealed gel's efficacy and tolerability; half of the patients showed a complete cure, and 90% showed improvement within 6 weeks. Only 10-12% of the patients reported side effects. In summary, transforming TCA solution into a gel enabled its application and handling in a practical manner by physicians and patients alike, while maintaining its efficacy as a tissue-destroying agent. Moreover, it is economic and easy to apply, rendering it a promising formulation for similar conditions requiring controlled tissue ablation.

Spidroin in carbopol-based gel promotes wound healing in earthworm's skin model.

Spider silk's regenerative, biocompatible, and antimicrobial properties render it a promising biomaterial for wound healing promotion. Spidroin as the main protein component of spider silks was used in this study to evaluate the potential effects on wound healing via topical application of novel spidroin-containing carbopol 934 (CP934) gel. Spidroin was extracted, formulated into CP934 gel, and characterized both in vitro and in vivo. Spidroin gel was translucent and brownish-yellow in color. An optimum viscosity was obtained at 0.6% CP934 at neutral pH. Optimized spidroin gel (0.6% CP934) effectively inhibited the growth of clinical bacterial isolates of methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA) and Escherichia coli at 440 µg/mL with MIC values of 0.98, 4.6, and 8.2 µg/mL, respectively. Optimized spidroin gel was evaluated for wound healing via topical application on wounds surgically induced in Allolobophora caliginosa earthworms used as a robust human skin model. After application for three consecutive days, dramatic reductions in wound closure and reepithelialization duration were observed macroscopically and via histological studies (light and electron microscopy) when compared with control. In conclusion, these results show that spidroin gel is a promising promoter for wound healing, and further studies would be directed toward investigating mechanisms underlying this effect.

Release kinetics study of poorly water-soluble drugs from nanoparticles: are we doing it right?

In vitro drug release kinetics studies are routinely performed to examine the ability of new drug formulations to modulate drug release. The underlying assumption is that the studies are performed in a sufficiently dilute solution, where the drug release is not limited by the solubility and the difference in release kinetics profile reflects the performance of a drug carrier in vivo. This condition is, however, difficult to meet with poorly water-soluble drug formulations, as it requires a very large volume of release medium relative to the formulation mass, which makes it challenging to measure the drug concentration accurately. These difficulties are aggravated with nanoparticle (NP) formulations, which are hard to separate from the release medium and thus require a dialysis bag or repeated high-speed centrifugation for sampling. Perhaps for these reasons, drug release kinetics studies of NPs of poorly water-soluble drugs are often performed in suboptimal conditions in which the NPs are not sufficiently diluted. However, such a practice can potentially underestimate drug release from NPs, leading to an inaccurate prediction that the NPs will attenuate the drug activity in vivo. Here we perform release kinetics studies of two different NP formulations of paclitaxel, a representative poorly water-soluble drug, according to common practices in the literature. We find that the drug release from NPs can be substantially underestimated depending on the choice of the release medium, NP/medium ratio, and handling of release samples. We discuss potential consequences of underestimating drug release, ending with suggestions for future studies with NP formulations of poorly water-soluble drugs.

Dual-responsive in situ gelling polymer matrix for tunable ketamine general anesthesia in experimental animals.

Animal experimentation is a critical part of the drug development process and pharmaceutical research. General anesthesia is one of the most common procedures. Careful administration and dosing of anesthetics ensure animal safety and study success. However, repeated injections are needed to maintain anesthesia, leading to adverse effects. Ketamine, a dissociative anesthetic, is commonly used for inducing anesthesia in animals and suffers from a short half-life requiring repeated dosing. Herein, we report a novel system for controlled anesthesia post-intraperitoneal administration. A polymer solution called "premix" was developed using two stimuli-responsive polymers, Pluronic (PF) and Carbopol (CP). As the premix was mixed with ketamine solution and injected, it underwent in situ gelation, hence controlling ketamine release and anesthesia. The PF and CP concentrations were optimized for the gelation temperature and viscosity upon mixing with the ketamine solution. The optimal premix/ketamine formulation (1.5:1) was liquid at room temperature and gel at physiological conditions with favorable mucoadhesion and rheology. Premix retarded the release of ketamine, translating to tunable anesthesia in vivo. Anesthesia duration and recovery were tunable per ketamine dose with minimal side effects. Therefore, we propose the implementation of PF/CP premix as a vehicle for general anesthesia in animals for optimal duration and effect.

Nanoparticle characterization: state of the art, challenges, and emerging technologies.

Nanoparticles have received enormous attention as a promising tool to enhance target-specific drug delivery and diagnosis. Various in vitro and in vivo techniques are used to characterize a new system and predict its clinical efficacy. These techniques enable efficient comparison across nanoparticles and facilitate a product optimization process. On the other hand, we recognize their limitations as a prediction tool, due to inadequate applications and overly simplified test conditions. We provide a critical review of in vitro and in vivo techniques currently used for evaluation of nanoparticles and introduce emerging techniques and models that may be used complementarily.

Design and optimization of metformin hydrophobic ion pairs for efficient encapsulation in polymeric drug carriers.

Loading small molecular weight hydrophilic drugs into polymeric carriers is a challenging task. Metformin hydrochloride (MET) is a highly soluble oral antidiabetic drug of small size and high cationic charge. Hydrophobic ion pairing (HIP) is an approach for reversible modulation of solubility and hydrophilicity of water-soluble drugs via complexation with oppositely charged molecules. Herein, we prepared MET ion pairs and carefully studied and characterized MET interaction with different ligands, with the aim of increasing MET lipophilicity and loading efficiency. HIP was successful using three hydrophilic anionic ligands; sodium dodecyl sulphate (SDS) Carbopol (CB) and tannic acid (TA). Electrostatic interaction and hydrogen bonding drove the complexation per spectroscopic and thermal studies. Complexation efficiency depended on ligand type and charge ratio. While complexes had varying interaction strengths, the excessive stability of TA/MET resulted in unfavorable poor MET dissociation. Notably, HIP imparted a 450 and tenfold lipophilicity increase for SDS/MET and CB/MET, respectively. The latter showed favorable controlled, yet complete release of MET at pH 6.8 and was loaded into alginate beads. Complex bulkiness and decreased lipophilicity resulted in a dramatic 88% increase of MET loading, demonstrating the success of HIP as a simple, efficient and applicable approach for modulating drug's properties.

Ionic liquid of ketoprofen-piperine modulates the pharmaceutical and therapeutic characters of ketoprofen.

Efficiency of drug delivery is product of drug properties and formulation design. Modulating drug's unfavorable properties such as poor solubility or permeation is the first step towards optimum delivery. By combining a drug with a selected bulky counter ion, it can be transformed into a low-melting point salt, i.e., an ionic liquid (IL), with favorable physicochemical properties. In this study, we prepared a novel IL of anti-inflammatory drug, ketoprofen (KP), to enable its transdermal administration. KP was paired with piperine (PI) forming equimolar KP-PI IL, via solvent evaporation. KP-PI IL showed extended stability. Thermal analysis and X-ray diffractometry proved that KP was transformed into a low-melting point amorphous form, while spectroscopic analysis and computational studies demonstrated that KP-PI interaction was mediated by hydrogen bonding. In the IL form, KP's solubility increased due to IL formation by 71 to 83%, while 218% more KP was permeated through rat skin in the IL form, than in a KP/PI mixture. Importantly, upon transdermal administration to rats with induced paw edema; KP-PI IL resulted in a 68% less paw swelling than KP/PI mixture. These findings demonstrate the utility of IL as an economic, simple and efficient strategy for improving the therapeutic application of drugs/drug combinations.

Self-assembled tannic acid complexes for pH-responsive delivery of antibiotics: Role of drug-carrier interactions.

Self-assembled particles, based on non-covalent interactions, are attractive drug carriers with a relatively simple structure and easy preparation. Tannic acid (TA) is an anionic polyphenolic compound with a wide range of molecular interactions and diverse applications in drug delivery research. Here, we propose the use of TA complexes with cationic antibiotics as a new pH-responsive drug carrier of high drug loading and optimal stability. TA complexes were prepared with three water-soluble antibiotics; colistin sulfate (COL), gentamicin sulfate (GEN) and gatifloxacin (GAT). Complexes' size ranged from several-hundred nanometers to few microns. For selected particles, drug loading ranged from 30 to 36%. Importantly, we demonstrate the impact of drug-carrier interactions, studied via infrared spectroscopy and molecular modeling, on final complex stability and performance; the complexes resisted dissociation in presence of serum at physiological pH to variable degrees and showed different drug release profiles. However, all complexes dissociated upon medium acidification, releasing their drug payload and demonstrating expected antibacterial effect. These results demonstrate that TA/antibiotic self-assembled complexes represent an excellent carrier for pH-sensitive delivery of water-soluble drugs. In addition to system's simplicity and low cost, complexes were easily prepared with high drug loading and desirable pH-dependent association/dissociation profile.

Dual-responsive lidocaine in situ gel reduces pain of intrauterine device insertion.

The most effective and safe contraceptive method, intrauterine devices (IUDs), is still underutilized due to the pain barrier during IUD insertion. Lidocaine, a well-known local anesthetic, can be used to relieve IUD insertion pain. This study aimed at formulation, in vitro, in vivo and clinical evaluation of a novel lidocaine dual-responsive in situ gel. Pluronic and Gelrite® were used as thermosenstive and ion-activated polymers, respectively. In situ gels containing 2% lidocaine, pluronics and/or Gelrite® were prepared. The optimized dual-responsive formula (F5) was clear, with 95% drug content, free flowing at room temperature and gel at vaginal temperature (Tgel of 28 °C). This optimized dual-responsive in situ gel was found to be superior to single-responsive one due to presence of Gelrite®, imparting resistance to dilution effect of simulated vaginal fluids. DSC thermograms revealed no interaction between formulation components. Biocompatibility study showed no degeneration, necrosis or inflammation. Optimized dual-responsive in situ gel was further evaluated for pain reduction efficiency via a pilot randomized, double-blinded, placebo-controlled clinical trial showing ease of self-administeration by patients and significant pain reduction induced at all steps of IUD insertion. In conclusion, lidocaine dual-responsive in situ gel can be effectively used in prevention of pain during IUD insertion.

Surface functionalization of polymeric nanoparticles for tumor drug delivery: approaches and challenges.

INTRODUCTION: For years, injectable polymeric nanoparticles (NPs) have been developed for delivering therapeutic agents to the tumors. Frequently, NPs surface have been modified with different moieties and/or ligands to impart stealth effect and/or elicit specific cellular interactions, both known to dramatically affect the in vivo fate and efficacy of these NPs. Areas covered: We discuss different types of ligands and molecules used for surface functionalization of polymeric NPs for tumor drug delivery. First, we summarize methods used through the literature for surface modification of polymeric NPs, then discuss challenges that face researchers either in decorating NPs with desired surface functionalities, characterizing functionalized surfaces or achieving intended cellular interactions and in vivo effects. Expert opinion: Modification of NP surfaces dramatically alters their behavior and favorably enhances their therapeutic efficacy. Choice of surface ligand/functionality should be based on intended therapeutic outcomes, taking into consideration the potential of clinical translation and scale up of the developed systems.

Tannic acid-mediated surface functionalization of polymeric nanoparticles.

Polymeric nanoparticles (NPs) are decorated with various types of molecules to control their functions and interactions with specific cells. We previously used polydopamine (pD) to prime-coat poly(lactic-co-glycolic acid) (PLGA) NPs and conjugated functional ligands onto the NPs via the pD coating. In this study, we report tannic acid (TA) as an alternative prime coating that is functionally comparable to pD but does not have drawbacks of pD such as optical properties and interference of ligand characterization. TA forms a stable and optically inert coating on PLGA NPs, which can accommodate albumin, chitosan, and folate-terminated polyethylene glycol to control the cell-NP interactions. Moreover, TA coating allows for surface loading of polycyclic planar aromatic compounds. TA is a promising reactive intermediate for surface functionalization of polymeric NPs.

Polymer-iron oxide composite nanoparticles for EPR-independent drug delivery.

Nanoparticle (NP)-based approaches to cancer drug delivery are challenged by the heterogeneity of the enhanced permeability and retention (EPR) effect in tumors and the premature attrition of payload from drug carriers during circulation. Here we show that such challenges can be overcome by a magnetophoretic approach to accelerate NP delivery to tumors. Payload-bearing poly(lactic-co-glycolic acid) NPs were converted into polymer-iron-oxide nanocomposites (PINCs) by attaching colloidal Fe3O4 onto the surface, via a simple surface modification method using dopamine polymerization. PINCs formed stable dispersions in serum-supplemented medium and responded quickly to magnetic field gradients above 1 kG/cm. Under the field gradients, PINCs were rapidly transported across physical barriers and into cells and captured under flow conditions similar to those encountered in postcapillary venules, increasing the local concentration by nearly three orders of magnitude. In vivo magnetophoretic delivery enabled PINCs to accumulate in poorly vascularized subcutaneous SKOV3 xenografts that did not support the EPR effect. In vivo magnetic resonance imaging, ex vivo fluorescence imaging, and tissue histology all confirmed that the uptake of PINCs was higher in tumors exposed to magnetic field gradients, relative to negative controls.

Low molecular weight chitosan-coated polymeric nanoparticles for sustained and pH-sensitive delivery of paclitaxel.

Low molecular weight chitosan (LMWC) is a promising polymer for surface modification of nanoparticles (NPs), which can impart both stealth effect and electrostatic interaction with cells at mildly acidic pH of tumors. We previously produced LMWC-coated NPs via covalent conjugation to poly(lactic-co-glycolic) acid (PLGA-LMWC NPs). However, this method had several weaknesses including inefficiency and complexity of the production as well as increased hydrophilicity of the polymer matrix, which led to poor drug release control. Here, we used the dopamine polymerization method to produce LMWC-coated NPs (PLGA-pD-LMWC NPs), where the core NPs were prepared with PLGA that served best to load and retain drugs and then functionalized with LMWC via polydopamine layer. The PLGA-pD-LMWC NPs overcame the limitations of PLGA-LMWC NPs while maintaining their advantages. First of all, PLGA-pD-LMWC NPs attenuated the release of paclitaxel to a greater extent than PLGA-LMWC NPs. Moreover, PLGA-pD-LMWC NPs had a pH-dependent surface charge profile and cellular interactions similar to PLGA-LMWC NPs, enabling acid-specific NP-cell interaction and enhanced drug delivery to cells in weakly acidic environment. Although the LMWC layer did not completely prevent protein binding in serum solution, PLGA-pD-LMWC NPs showed less phagocytic uptake than bare PLGA NPs.

Extracellularly activatable nanocarriers for drug delivery to tumors.

INTRODUCTION: Nanoparticles (NPs) for drug delivery to tumors need to satisfy two seemingly conflicting requirements: they should maintain physical and chemical stability during circulation and be able to interact with target cells and release the drug at desired locations with no substantial delay. The unique microenvironment of tumors and externally applied stimuli provide a useful means to maintain a balance between the two requirements. AREAS COVERED: We discuss nanoparticulate drug carriers that maintain stable structures in normal conditions but respond to stimuli for the spatiotemporal control of drug delivery. We first define the desired effects of extracellular activation of NPs and frequently used stimuli and then review the examples of extracellularly activated NPs. EXPERT OPINION: Several challenges remain in developing extracellularly activatable NPs. First, some of the stimuli-responsive NPs undergo incremental changes in response to stimuli, losing circulation stability. Second, the applicability of stimuli in clinical settings is limited due to the occasional occurrence of the activating conditions in normal tissues. Third, the construction of stimuli-responsive NPs involves increasing complexity in NP structure and production methods. Future efforts are needed to identify new targeting conditions and increase the contrast between activated and nonactivated NPs while keeping the production methods simple and scalable.