Controlled release of vancomycin from poloxamer 407 gels

Improving material properties of a poloxamer P407 hydrogel-based hydroxyapatite bone substitute material by adding silica-A comparative in vivo study

The structure and handling properties of a P407 hydrogel-based bone substitute material (BSM) might be affected by different poloxamer P407 and silicon dioxide (SiO2) concentrations. The study aimed to compare the mechanical properties and biological parameters (bone remodeling, BSM degradation) of a hydroxyapatite: silica (HA)-based BSM with various P407 hydrogels in vitro and in an in vivo rat model. Rheological analyses for mechanical properties were performed on one BSM with an SiO2-enriched hydrogel (SPH25) as well on two BSMs with unaltered hydrogels in different gel concentrations (PH25 and PH30). Furthermore, the solubility of all BSMs were tested. In addition, 30 male Wistar rats underwent surgical creation of a well-defined bone defect in the tibia. Defects were filled randomly with PH30 (n = 15) or SPH25 (n = 15). Animals were sacrificed after 12 (n = 5 each), 21 (n = 5 each), and 63 days (n = 5 each). Histological evaluation and histomorphometrical quantification of new bone formation (NB;%), residual BSM (rBSM;%), and soft tissue (ST;%) was conducted. Rheological tests showed an increased viscosity and lower solubility of SPH when compared with the other hydrogels. Histomorphometric analyses in cancellous bone showed a decrease of ST in PH30 (p = .003) and an increase of NB (PH30: p = .001; SPH: p = .014) over time. A comparison of both BSMs revealed no significant differences. The addition of SiO2 to a P407 hydrogel-based hydroxyapatite BSM improves its mechanical stability (viscosity, solubility) while showing similar in vivo healing properties compared to PH30. Additionally, the SiO2-enrichment allows a reduction of poloxamer ratio in the hydrogel without impairing the material properties.

Fosfatriclaben, a prodrug of triclabendazole: Preparation, stability, and fasciolicidal activity of three new intramuscular formulations

In this study, we present the preparation, stability, and in vivo fasciolicidal activity of three new intramuscular formulations in sheep of a prodrug based on triclabendazole, named fosfatriclaben. The new formulations were ready-to-use aqueous solutions with volumes recommended for intramuscular administration in sheep. The use of poloxamers (P-407 and P-188) and polysorbates (PS-20 and PS-80) in the new formulations improved the aqueous solubility of fosfatriclaben by 8-fold at pH 7.4. High-performance liquid chromatography with UV detection was used to evaluate the stability of fosfatriclaben in the three formulations. High recovery (> 90%) of fosfatriclaben was found for all formulations after exposure at 57 ± 2 °C for 50 h. The three intramuscular formulations showed high fasciolicidal activity at a dose of 6 mg/kg, which was equivalent to the triclabendazole content. The fasciolicidal activity of fosfatriclaben was similar to commercial oral (Fasimec®) and intramuscular (Endovet®) triclabendazole formulations at a dose of 12 mg/kg. In the in vivo experiments, all formulations administered intramuscularly reduced egg excretion by 100%, and formulations F1, F2, and F3 presented fasciolicidal activities of 100%, 100%, and 99.6%, respectively.

Selection of Excipients for the Preparation of Vancomycin-Loaded Poly(D,L-lactide-co-glycolide) Microparticles with Extended Release by Emulsion Spray Drying

The aim of this study was to relate the composition of the W/O emulsion used as a starting fluid in the spray-drying process to the quality of the dry polymer particles obtained in terms of physical-chemical properties, compatibility and drug release performance. Four W/O emulsions containing vancomycin hydrochloride (VAN), an encapsulating PLGA polymer and Poloxamer® 407, chitosan and/or sorbitan monooleate as stabilisers were spray-dried using an ultrasonic atomising nozzle. The microparticles obtained were micron-sized, with a volume mean diameter between 43.2 ± 0.3 and 64.0 ± 12.6 µm, and spherical with a mostly smooth, non-porous surface and with high drug loading (between 14.5 ± 0.6 and 17.1 ± 1.9% w/w). All formulations showed a prolonged and biphasic VAN release profile, with diffusion being the primary release mechanism. Microparticles prepared from the emulsions with Poloxamer® 407 and sorbitan monooleate released VAN rapidly and completely within one day. The release of VAN from microparticles prepared from the emulsion without additives or with chitosan in the inner aqueous phase was significantly decreased; after four days, a cumulative release of 65% and 61%, respectively, was achieved. Microparticles with encapsulated chitosan had the largest mean particle diameter and the slowest release of VAN.

Pluronic F-68 and F-127 Based Nanomedicines for Advancing Combination Cancer Therapy

Pluronics are amphiphilic triblock copolymers composed of two hydrophilic poly (ethylene oxide) (PEO) chains linked via a central hydrophobic polypropylene oxide (PPO). Owing to their low molecular weight polymer and greater number of PEO segments, Pluronics induce micelle formation and gelation at critical micelle concentrations and temperatures. Pluronics F-68 and F-127 are the only United States (U.S.) FDA-approved classes of Pluronics and have been extensively used as materials for living bodies. Owing to the fascinating characteristics of Pluronics, many studies have suggested their role in biomedical applications, such as drug delivery systems, tissue regeneration scaffolders, and biosurfactants. As a result, various studies have been performed using Pluronics as a tool in nanomedicine and targeted delivery systems. This review sought to describe the delivery of therapeutic cargos using Pluronic F-68 and F-127-based cancer nanomedicines and their composites for combination therapy.

Boosting the photodynamic activity of erythrosine B by using thermoresponsive and adhesive systems containing cellulose derivatives for topical delivery

Erythrosine displays potential photodynamic activity against microorganisms and unhealthy cells. However, erythrosine has high hydrophilicity, negatively impacting on permeation through biological membranes. Combining biological macromolecules and thermoresponsive polymers may overcome these erythrosine-related issues, enhancing retention of topically applied drugs. The aim of this work was to investigate the performance of adhesive and thermoresponsive micellar polymeric systems, containing erythrosine in neutral (ERI) or disodium salt (ERIs) states. Optimized combinations of poloxamer 407 (polox407) and sodium carboxymethylcellulose (NaCMC) or hydroxypropyl methylcellulose (HPMC) were used as platforms for ERI/ERIs delivery. The rheological and mechanical properties of the systems was explored. Most of the formulations were plastic, thixotropic and viscoelastic at 37 °C, with suitable gelation temperature for in situ gelation. Mechanical parameters were reduced in the presence of the photosensitizer, improving the softness index. Bioadhesion was efficient for all hydrogels, with improved parameters for mucosa in contrast to skin. Formulations composed of 17.5 % polox407 and 3 % HPMC or 1 % NaCMC with 1 % (w/w) ERI/ERIs could release the photosensitizer, reaching different layers of the skin/mucosa, ensuring enough production of cytotoxic species for photodynamic therapy. Functional micelles could boost the photodynamic activity of ERI and ERIs, improving their delivery and contact time with the cells.

Lyotropic liquid crystal elastomers for drug delivery

Silicone elastomers like polydimethylsiloxane (PDMS) possess a combination of attractive material and biological properties motivating their widespread use in biomedical applications. Development of elastomers with capacity to deliver active therapeutic substances in the form of drugs is of particular interest to produce medical devices with added functionality. In this work, silicone-based lyotropic liquid crystal elastomers with drug-eluting functionality were developed using PDMS and triblock copolymer (diacrylated Pluronic F127, DA-F127). Various ternary PDMS-DA-F127-H₂O compositions were explored and evaluated. Three compositions were found to have specific properties of interest and were further investigated for their nanostructure, mechanical properties, water retention capacity, and morphology. The ability of the elastomers to encapsulate and release polar and nonpolar substances was demonstrated using vancomycin and ibuprofen as model drugs. It was shown that the materials could deliver both types of drugs with a sustained release profile for up to 6 and 5 days for vancomycin and ibuprofen, respectively. This works demonstrates a lyotropic liquid crystal, silicone-based elastomer with tailorable mechanical properties, water retention capacity and ability to host and release polar and nonpolar active substances.

Multifunctional Surface Modification of PDMS for Antibacterial Contact Killing and Drug-Delivery of Polar, Nonpolar, and Amphiphilic Drugs

Medical device-associated infections pose major clinical challenges that emphasize the need for improved anti-infective biomaterials. Polydimethylsiloxane (PDMS), a frequently used elastomeric biomaterial in medical devices, is inherently prone to bacterial attachment and associated infection formation. Here, PDMS surface modification strategy is presented consisting of a cross-linked lyotropic liquid crystal hydrogel microparticle coating with antibacterial functionality. The microparticle coating composed of cross-linked triblock copolymers (diacrylated Pluronic F127) was deposited on PDMS by physical immobilization via interpenetrating polymer network formation. The formed coating served as a substrate for covalent immobilization of a potent antimicrobial peptide (AMP), RRPRPRPRPWWWW-NH₂, yielding high contact-killing antibacterial effect against Staphylococcus epidermidis and Staphylococcus aureus. Additionally, the coating was assessed for its ability to selectively host polar, amphiphilic, and nonpolar drugs, resulting in sustained release profiles. The results of this study put forward a versatile PDMS modification strategy for both contact-killing antibacterial surface properties and drug-delivery capabilities, offering a solution for medical device-associated infection prevention.

Case report: Use of penicillin G potassium in poloxamer 407 gel to aid in healing of an equine sublingual abscess

The use of poloxamer 407 gels have been reported in several studies to prolong the release of drugs at the injection site. Oral lesions unrelated to dental disease are rare but may result in ulceration and sequestration of bone. To date, there have been no reports on the use of penicillin G potassium poloxamer 407 gel and its effect on wound healing. The present case report describes the use of a penicillin G potassium poloxamer 407 gel for the treatment of a sublingual abscess involving the mandible in a 20 year old Arabian mare who initially presented with acute onset of dysphagia, hypersalivation, and a mass under the tongue. A presumptive diagnosis of lingual cellulitis was made, and a sublingual abscess ruptured on day 7 of hospitalization. In this case, poloxamer 407 gel was used to decrease wound contamination, protect the exposed mandible, and potentially prolong the release of penicillin G potassium into the wound.

Sustained Delivery of Lactoferrin Using Poloxamer Gels for Local Bone Regeneration in a Rat Calvarial Defect Model

Lactoferrin (LF) is a multifunctional milk glycoprotein that promotes bone regeneration. Local delivery of LF at the bone defect site is a promising approach for enhancement of bone regeneration, but efficient systems for sustained local delivery are still largely missing. The aim of this study was to investigate the potential of the poloxamers for sustained delivery of LF to enhance local bone regeneration. The developed LF/poloxamer formulations were liquid at room temperature (20 °C) transforming to a sustained releasing gel depot at body temperature (37 °C). In vitro release studies demonstrated an initial burst release (~50%), followed by slower release of LF for up to 72 h. Poloxamer, with and without LF, increased osteoblast viability at 72 h (p < 0.05) compared to control, and the immune response from THP-1 cells was mild when compared to the suture material. In rat calvarial defects, the LF/poloxamer group had lower bone volume than the controls (p = 0.0435). No difference was observed in tissue mineral density and lower bone defect coverage scores (p = 0.0267) at 12 weeks after surgery. In conclusion, LF/poloxamer formulations support cell viability and do not induce an unfavourable immune response; however, LF delivery via the current formulation of LF200/poloxamer gel did not demonstrate enhanced bone regeneration and was not compatible with the rat calvarial defect model.

Enhancing the therapeutic use of biofilm-dispersing enzymes with smart drug delivery systems

Biofilm-dispersing enzymes degrade the extracellular polymeric matrix surrounding bacterial biofilms, disperse the microbial community and increase their susceptibility to antibiotics and immune cells. Challenges for the clinical translation of biofilm-dispersing enzymes involve their susceptibility to denaturation, degradation, and clearance upon administration in vivo. Drug delivery systems aim to overcome these limitations through encapsulation, stabilization and protection from the exterior environment, thereby maintaining the enzymatic activity. Smart drug delivery systems offer target specificity, releasing payloads at the site of infection while minimizing unnecessary systemic exposure. This review highlights critical advances of biofilm-dispersing enzymes as a novel therapeutic approach for biofilm-associated infections. We explore how smart, bio-responsive delivery systems overcome the limiting factors of biofilm-dispersing enzymes and summarize the key systems designed. This review will guide future developments, focusing on utilizing selective and specific therapies in a targeted fashion to meet the unmet therapeutic needs of biofilm infections.

Calcium-Enriched Nanofibrillated Cellulose/Poloxamer in-situ Forming Hydrogel Scaffolds as a Controlled Delivery System of Raloxifene HCl for Bone Engineering

PURPOSE

TEMPO-oxidized nanofibrillated cellulose (TONFC) originating from an agricultural waste (sugar cane) was utilized to prepare injectable in-situ forming hydrogel scaffolds (IHS) for regenerative medicine.

METHODS

TONFC was prepared and characterized for its morphology and chemical structure using TEM and FT-IR, respectively. The cold method was applied to prepare hydrogels. Various concentrations of poloxamer 407 were added to the prepared TONFC (0.5%w/w). Different sources of calcium, Fujicalin® (DCP) or hydroxyapatite (TCP), were used to formulate the aimed calcium-enriched raloxifene hydrochloride-loaded IHS. Gelation temperature, drug content, injectability and in-vitro drug release were evaluated along with the morphological characters. Cytocompatibility studies and tissue regeneration properties were assessed on Saos-2 cells.

RESULTS

TEM photograph of TONFC showed fibrous nanostructure. The selected formulation "Ca-IHS4" composed of TONFC+15% P407+10% TCP showed the most prolonged release pattern for 12 days with the least burst effect (about 25% within 24 h). SEM micro-photographs of the in-situ formed scaffolds showed a highly porous 3D structure. Cytocompatibility studies of formulation "Ca-IHS4" revealed the biocompatibility as well as improved cell adhesion, alkaline phosphatase enzyme activity and calcium ion deposition.

CONCLUSION

The outcomes suggest that Ca-IHS4 presents a simple, safe-line and non-invasive strategy for bone regeneration.

A novel BMP-2-loaded hydroxyapatite/beta-tricalcium phosphate microsphere/hydrogel composite for bone regeneration

Although bone morphogenetic protein (BMP) has potent osteoinductivity, the potential adverse events attributed to its burst release prevent its widespread clinical application. Therefore, there is a strong need for BMP delivery systems that maximize osteoinductivity while preventing adverse effects. We evaluated the bone-regenerating potential of NOVOSIS putty (NP), a novel composite combining hydroxyapatite, beta-tricalcium phosphate microsphere/poloxamer 407-based hydrogel, and recombinant human (rh) BMP-2. In vitro assessment of release kinetics by enzyme-linked immunosorbent assay demonstrated sustained release of rhBMP-2 from NP and burst release from collagen sponge (CS), and in vivo assessment of release kinetics by longitudinal tracking of fluorescently labeled rhBMP-2 showed a longer biological half-life of rhBMP-2 with NP than with CS. Furthermore, osteogenic gene expression in MC3T3-E1 cells was significantly higher after co-culture with NP than after co-culture with CS, suggesting that the sustained release of rhBMP-2 from NP effectively contributed to the differentiation of osteoblasts. In a rat spinal fusion model, the volume and quality of newly formed bone was higher in the NP group than in the CS group. Use of NP results in efficient bone regeneration through sustained release of rhBMP-2 and improves the quality of BMP-induced bone.

Vesicular drug delivery for the treatment of topical disorders: current and future perspectives

OBJECTIVES

Vesicular drug delivery has become a useful approach for therapeutic administration of pharmaceutical compounds. Lipid vesicles have found application in membrane biology, immunology, genetic engineering and theragnostics. This review summarizes topical delivery, specifically dermal/transdermal, ocular and transungual, via these vesicles, including future formulation perspectives.

KEY FINDINGS

Liposomes and their subsequent derivatives, viz. niosomes, transferosomes, pharmacososmes and ethosomes, form a significant part of vesicular systems that have been successfully utilized in treating an array of topical disorders. These vesicles are thought to be a safe and effective mode of improving the delivery of lipophilic and hydrophilic drugs.

SUMMARY

Several drug molecules are available for topical disorders. However, physicochemical properties and undesirable toxicity have limited their efficacy. Vesicular delivery systems have the potential to overcome these shortcomings due to properties such as high biocompatibility, simplicity of surface modification and suitability as controlled delivery vehicles. However, incorporating these systems into environmentally responsive dispersants such as hydrogels, ionic liquids and deep eutectic solvents may further enhance therapeutic prowess of these delivery systems. Consequently, improved vesicular drug delivery can be achieved by considering combining some of these formulation approaches.

Development and In Vitro Evaluation of Controlled Release Viagra® Containing Poloxamer-188 Using Gastroplus™ PBPK Modeling Software for In Vivo Predictions and Pharmacokinetic Assessments

Sildenafil is the active substance in Viagra^® tablets, which is approved by the FDA to treat sexual dysfunction in men. Poor solubility and short half-life, however, can limit the span of its effectiveness. Therefore, this study focused on an oral controlled release matrix system with the aim to improve solubility, control the drug release, and sustain the duration of drug activity. The controlled release matrices were prepared with poloxamer-188, hydroxypropyl methylcellulose, and magnesium stearate. Various formulations of different ratios were developed, evaluated in vitro, and assessed in silico. Poloxamer-188 appeared to have a remarkable influence on the release profile of sildenafil citrate. In general, the rate of drug release decreased as the amount of polymer was gradually increased in the matrix system, achieving a maximum release period over 12 h. The in silico assessment by using the GastroPlus™ PBPK modeling software predicted a significant variation in C_max, t_max, t_1/2, and AUC_0-t among the formulations. In conclusion, the combination of polymers in matrix systems can have substantial impact on controlling and modifying the drug release pattern.

(Macro)molecular self-assembly for hydrogel drug delivery

Hydrogels prepared via self-assembly offer scalable and tunable platforms for drug delivery applications. Molecular-scale self-assembly leverages an interplay of attractive and repulsive forces; drugs and other active molecules can be incorporated into such materials by partitioning in hydrophobic domains, affinity-mediated binding, or covalent integration. Peptides have been widely used as building blocks for self-assembly due to facile synthesis, ease of modification with bioactive molecules, and precise molecular-scale control over material properties through tunable interactions. Additional opportunities are manifest in stimuli-responsive self-assembly for more precise drug action. Hydrogels can likewise be fabricated from macromolecular self-assembly, with both synthetic polymers and biopolymers used to prepare materials with controlled mechanical properties and tunable drug release. These include clinical approaches for solubilization and delivery of hydrophobic drugs. To further enhance mechanical properties of hydrogels prepared through self-assembly, recent work has integrated self-assembly motifs with polymeric networks. For example, double-network hydrogels capture the beneficial properties of both self-assembled and covalent networks. The expanding ability to fabricate complex and precise materials, coupled with an improved understanding of biology, will lead to new classes of hydrogels specifically tailored for drug delivery applications.

A meta-analysis of bone cement mediated antibiotic release: Overkill, but a viable approach to eradicate osteomyelitis and other infections tied to open procedures

A number of clinical studies have highlighted the success of antibiotics formulated at concentrations between 0 and 6% w/w into bone cements to address localized infections. Separately, some commercial manufacturers have produced gentamycin-infused bone cement mixtures as a countermeasure to infection. The anecdotal evidence suggests that antibiotic infused cements can help eradicate or delay the onset of infections. Quantifying the functionality of that response is more challenging. We have surveyed the literature to identify studies in which controlled drug release or mechanical behavioral assessments have been conducted on drug-infused cements. The focus here is on vancomycin (VAN) in part due to its higher potency relative to gentamycin and its more common usage for staph infections. Takeaways from the limited pool of research studies indicate that large fractions (>99%) of the infused vancomycin remain sequestered in the cement and aren't bioavailable after solidification. Antibiotic fluence ranged from 1 to 283 μg/cm²hr. The initial strength of the various antibiotic loaded samples as produced were 52-96 MPa. Simulated exposures in a fluid environment by submersion reduced the antibiotic loaded strengths between 3 and 29%. Some strength measurements were noted below the ASTM F451 standard for acrylic bone cement although drug releasing spacers likely have different requirements. The glassy behavior of the cured cement led to both vancomycin and gentamicin having low permeability and a burst response. Smaller drug molecules and more gel-like immobilization matrices with lower glass transition temperatures offer higher potential for larger and more comprehensive drug bioavailability.

Thermosensitive Gels Used to Improve Microneedle-Assisted Transdermal Delivery of Naltrexone

Transdermal delivery of naltrexone (NTX) can be enhanced using microneedles, although micropores generated this way can reseal by 48 h in humans, which prevents further drug delivery from a formulation. Poloxamer 407 (P407) is a thermosensitive polymer that may extend microneedle-assisted NTX delivery time by creating an in situ gel depot in the skin. We characterized gelation temperature, drug release, and permeation of P407 gels containing 7% NTX-HCl. To investigate microneedle effects on NTX-HCl permeation, porcine skin was treated with microneedles (600 or 750 μm length), creating 50 or 100 micropores. The formulations were removed from the skin at 48 h to simulate the effect of micropores resealing in vivo, when drug delivery is blunted. Gelation temperature increased slightly with addition of NTX-HCl. In vitro NTX-HCl release from P407 formulations demonstrated first order release kinetics. Microneedle treatment enhanced NTX-HCl permeation both from aqueous solution controls and P407 gels. Steady-state flux was overall lower in the P407 conditions compared to the aqueous solution, though ratios of AUCs before and after gel removal demonstrate that P407 gels provide more sustained release even after gel removal. This may be beneficial for reducing the required application frequency of microneedles for ongoing treatment.

Autoclaving of Poloxamer 407 hydrogel and its use as a drug delivery vehicle

With antibiotic-resistant bacteria becoming increasingly prevalent, biomaterials capable of targeted, in situ drug delivery are urgently needed. The synthetic polymer Poloxamer 407 (P407) is of particular interest due to its thermoreversible gelation. Clinical use of P407 typically involves sterilization via autoclaving, but the effects of these extreme environmental conditions on hydrogel water content, rheological properties and efficacy as a drug delivery vehicle remain unknown. The aim of this study was to investigate the effects of autoclaving on the properties of P407 hydrogel. Autoclaving reduced hydrogel water content due to evaporation, thus increasing the polymer weight fraction of the hydrogels. In contrast, except for a reduction in gelation temperature following autoclaving, autoclaved hydrogels had similar rheological properties as nonautoclaved hydrogels. In vitro, autoclaving did not hinder the hydrogel's efficacy as a carrier for vancomycin antibiotic, and P407 (with and without vancomycin) had a bactericidal effect on planktonic Staphylococcus aureus. An in vivo pilot study using P407 to deliver bacteriophage highlighted the need for additional understanding of the functionality of the hydrogel for surgical applications. In conclusion, P407 hydrogel water content and gelation temperature were reduced by autoclave sterilization, while other rheological properties and the efficacy of the biomaterial as a delivery vehicle for vancomycin in vitro were unaffected.

Nano Co-Crystal Embedded Stimuli-Responsive Hydrogels: A Potential Approach to Treat HIV/AIDS

Currently, the human immunodeficiency virus (HIV) that causes acquired immunodeficiency syndrome (AIDS) can only be treated successfully, using combination antiretroviral (ARV) therapy. Lamivudine (3TC) and zidovudine (AZT), two compounds used for the treatment of HIV and prevention of disease progression to AIDS are used in such combinations. Successful therapy with 3TC and AZT requires frequent dosing that may lead to reduced adherence, resistance and consequently treatment failure. Improved toxicity profiles of 3TC and AZT were observed when combined as a nano co-crystal (NCC). The use of stimuli-responsive delivery systems provides an opportunity to overcome the challenge of frequent dosing, by controlling and/or sustaining delivery of drugs. Preliminary studies undertaken to identify a suitable composition for a stimulus-responsive in situ forming hydrogel carrier for 3TC-AZT NCC were conducted, and the gelation and erosion time were determined. A 25% w/w Pluronic® F-127 thermoresponsive hydrogel was identified as a suitable carrier as it exhibited a gelation time of 5 min and an erosion time of 7 days. NCC-loaded hydrogels were evaluated using in vitro dissolution and cytotoxicity assays. In vitro dissolution undertaken using membrane-less diffusion over 168 h revealed that 3TC and AZT release from NCC-loaded hydrogels was complete and followed zero-order kinetic processes, whereas those loaded with the micro co-crystal and physical mixture were incomplete and best described using the Korsmeyer-Peppas kinetic model. The release of AZT and 3TC from the physical mixture and MCC-loaded gel exhibited a value for n of 0.595 for AZT release from the physical mixture and 0.540 for the MCC technology, whereas the release exponent for 3TC was 0.513 for the physical mixture and 0.557 for the MCC technology indicating that diffusion and erosion controlled 3TC and AZT release. In vitro cytotoxicity assay data revealed that the addition of NCC to the thermoresponsive hydrogel resulted in an improved cell viability of 88.0% ± 5.0% when compared to the cell viability of the NCC of 76.9% ± 5.0%. The results suggest that the use of a thermoresponsive nanosuspension may have the potential to be delivered as an intramuscular injection that can subsequently increase bioavailability and permit dose reduction and/or permit use of a longer dosing frequency.

Characterization of a Topically Testable Model of Burn Injury on Human Skin Explants

Severe burn injuries remain a major health problem due to high rates of mortality, residual morbidity, and/or aesthetic damages. To find new therapies aimed at promoting a harmonious healing of skin burns, it is important to develop models which take into account the unique properties of the human skin. Based on previously described models of burn injury performed on human skin explants, we hypothesized that maintaining explants under constant tension forces would allow to more closely reproduce the pathophysiological processes of skin remodeling. We thus. Here, we set up and characterized an improved model of deep second-degree burn injury on ex vivo cultured human skin explants at air-liquid interface and maintained under conditions of constant tension forces. A spontaneous re-epithelialization of the lesion was observed 8 to 9 days post burn and was found to rely on the proliferation of basal keratinocytes at the wound edges. Collagen VII at the dermo-epidermal junction reformed along with the progression of re-epithelializatio and a synthesis of procollagen III was observed in the dermis at the wound site. These findings indicate that our model is suitable for the assessment of clinically-relevant therapies aimed at modulating the kinetics of re-epithelialization and/or the activation of fibroblasts following skin burn injuries. In this regard, we evaluated the use of a thermoreversible poloxamer hydrogel as a vehicle for topically-testable therapeutic molecules. Our data showed that, although useful for drug formulation, the p407/p188 poloxamer hydrogel induces a delay of skin re-epithelialization in humans skin explants submitted to experimental burn injury.

Investigating the Potential to Deliver and Maintain Plasma and Brain Levels of a Novel Practically Insoluble Methuosis Inducing Anticancer Agent 5-Methoxy MOMIPP Through an Injectable In Situ Forming Thermoresponsive Hydrogel Formulation

A new indole based chalcone molecule MOMIPP induced methuosis mediated cell death in gliobastoma and other cancer cell lines. But the drug was insoluble in water and had a very short plasma half-life. The purpose of this work was to develop a formulation that can provide sustained levels of MOMIPP in vivo. Initial studies established drug solubility in various solvents. N-methyl pyrrolidone (NMP) was determined as an excellent solvent for the drug. Subsequently a poloxamer-407 based thermoreversible gel containing NMP was used to develop the formulation. Rheological studies were performed via oscillatory temperature mode, continuous shear analysis, and oscillatory frequency mode experiments. The mechanical properties of the formulations were tested using a texture profile analyzer. The gelation temperature and time of formulations increased with increasing amounts of NMP. However, the viscosity at 20 °C and storage modulus decreased as the amount of NMP increased. Characterization studies helped to identify the gel formulation that was used to administer the drug orally, sub-cutaneously, and intra-peritoneally. When the gel was given intraperitoneally the target plasma and brain levels of over 5 μM was maintained for about 8 h. Thus, a thermoreversible gel formulation that can deliver MOMIPP in animal studies was successfully developed.

The Rheolaser Master™ and Kinexus Rotational Rheometer® to Evaluate the Influence of Topical Drug Delivery Systems on Rheological Features of Topical Poloxamer Gel

Poloxamer 407 copolymer is a versatile and widely used thermo-reversible material. Its use has many advantages, such as bio-adhesion, enhanced solubilization of poorly water-soluble drugs and many applications fields like oral, rectal, topical, nasal drug administration. Hydrogels made up of Poloxamer 407 are characterized by specific rheological features, which are affected by temperature, concentration and presence of other compounds. A strategic approach in topical therapeutic treatments may be the inclusion of drug delivery systems, such as ethosomes, transfersomes and niosomes, into hydrogel poloxamer formulation. The evaluation of the interaction between colloidal carriers and the Poloxamer 407 hydrogel network is essential for a suitable design of an innovative topical dosage form. For this reason, the Rheolaser Master™, based on diffusing wave spectroscopy, and a Kinexus Rotational Rheometer were used to evaluate the influence of nanocarriers on the microrheological features of hydrogels. The advantages of the Rheolaser Master™ analyzer are: (i) its ability to determine viscoelastic parameter, without altering or destroying the sample and at rest (zero shear); (ii) possibility of aging analysis on the same sample. This study provide evidence that vesicular systems do not influence the rheological features of the gel, supporting the possibility to encapsulate an innovative system into a three-dimensional network.

In vitro elution of amikacin and Dispersin B from a polymer hydrogel

OBJECTIVE

To characterize the in vitro elution of amikacin and Dispersin B (β-N-acetylglucosaminidase) in a degradable hydrogel.

STUDY DESIGN

In vitro, prospective study.

METHODS

Amikacin (group A; 40 mg/mL), Dispersin B (group D; 70 μg/mL), or combined amikacin and Dispersin B (group AD; 40 mg/mL and 70 μg/mL, respectively) were added to a hydrogel. Ten aliquots per group were incubated in phosphate-buffered saline that was exchanged at 1, 4, 8, 12, and 24 hours and then once daily for 10 days. Eluted amikacin and Dispersin B were quantitated by using an amikacin reagent kit and a Dispersin B enzyme-linked immunosorbent assay kit, respectively. Time point drug concentrations were compared between groups by using repeated-measures analysis of variance, and total drug elution was compared by using an area under the curve calculation.

RESULTS

Amikacin alone, Dispersin B alone, and amikacin and Dispersin B combined together underwent rapid elution in the first 24 hours, followed by a gradual decrease over 10 days. The concentration of Dispersin B eluted in group D was higher at 1 day and lower from day 5 to day 10 compared with that in group AD. The concentration of amikacin eluted in group A was higher at 1, 4, and 8 hours and on day 10 and lower on day 1 compared with that in group AD. The total elution of amikacin was greater from group AD compared with that from group A (P = .02).

CONCLUSION

Combining amikacin and Dispersin B had an affect on the total elution of amikacin but not Dispersin B.

CLINICAL SIGNIFICANCE

The combination of amikacin and Dispersin B in a degradable hydrogel could allow local treatment of complex infections without the requirement for multiple invasive procedures.

Advances in Therapeutics and Delayed Drug Release

Reducing the frequency of drug administration in the treatment of exotic pets is advantageous because it may decrease handling frequency and thus potential stress and injury risk for the animal, increase owner compliance with the prescribed treatment, and decrease need for general anesthesia in patients that cannot be handled safely. Increasing efficient drug plasma concentration using sustained-released delivery systems is an appealing solution. Potential candidates that could provide a promising solution have been investigated in exotic pets. In this article, the technologies that are the closest to being integrated in exotic pet medicine are reviewed: osmotic pumps, nanoparticles, and hydrogels.

Theoretical Investigation of Design Space for Multi Layer Drug Eluting Bioresorbable Suture Threads

Background:

The work presented here is focused on the development of a comprehensive theoretical model for the description of drug release from a double - layer bioresorbable suture thread and the therapeutic efficacy of the active compounds delivered in the surrounding tissue.

Methods:

In particular, the system under investigation is composed of a core of slow-degrading polylactic- acid-co-ε-caprolactone (PLCL), where an antibiotic compound (Vancomycin) is loaded, surrounded by a shell of a fast-degrading polylactic-co-glycolic acid (PLGA) which contains an anesthetic drug (Lidocaine hydrochloride) for the post-surgical pain relief.

Results:

This system is of potential interest for the combined effects provided by the different active molecules, but the different release and polymer degradation dynamics, as well as their mutual influence, do not allow an intuitive a priori evaluation of device behavior, which can be rationalized through mathematical modeling. The model takes into account the main involved phenomena (polymer degradation and diffusion of the drugs within the device and the tissue, where they are metabolized) and their synergic effects on the overall system behavior.

Conclusion:

Model results are discussed in order to quantify the impact of the main design parameters on device performances, thanks to the use of phase diagrams (which show drug effect in time and space) whose insights are summarized in order to determine a design space according to the specific needs.

In vitro evaluation of poloxamer in situ forming gels for bedaquiline fumarate salt and pharmacokinetics following intramuscular injection in rats

The objective of this study was to evaluate in vitro and in vivo drug release from in situ forming gels prepared with poloxamer 338 (P338) and/or 407 (P407) in N-methyl-2-pyrrolidone (NMP)/water mixtures for the model compound bedaquiline fumarate salt. The impact of total poloxamer concentration (20%–25% (w/w)), P338/P407 ratio (100/0%–0/100% (w/w)) and NMP/water ratio (0/100%–25/75% (v/v)) on gel point temperature (GPT) was investigated via a design of experiments (DoE), showing that GPT decreased mainly with increasing poloxamer concentration and decreasing P338/P407 ratio, while the relation with NMP/water ratio was more complex resulting in a flexion. Based on the DoE, four formulations with 10 mg/g bedaquiline fumarate salt, a fixed NMP/water ratio of 25/75% (v/v) and varying total poloxamer concentration and P338/P407 ratio were selected for evaluation of gel erosion in vitro. The fastest eroding formulation had the lowest total poloxamer concentration (20% (w/w)) and the lowest P338/P407 ratio (20.4/79.6% (w/w)), while the formulation with the highest total poloxamer concentration (23.5% (w/w)) and highest P338/P407 ratio (100/0% (w/w)) showed the lowest gel erosion rate. These fast and slow eroding formulations showed a similar trend for in vitro drug release and in vivo pharmacokinetics after intramuscular (IM) injection in rats. In vivo t_max of the IM administered poloxamer in situ forming gels was about 6 h and a short-term sustained drug release was observed in vivo in rats up to 24 h after dosing, similar to a solution of bedaquiline fumarate salt in polyethylene glycol (PEG400)/water. In conclusion, IM administration of the evaluated poloxamer in situ forming gels may be useful for drugs that require a short-term sustained release, but is not able to extend drug release rates up to weeks or months.

Transforming an inert nanopolymer into broad-spectrum bactericidal by superstructure tuning

Poloxamer block copolymers (also known as Pluronic®) are particularly useful for drug delivery and self-assembly techniques. These nanopolymers are generally considered to be biologically inert and they were used to generate only bacteria repellent surfaces but keeps bacteria alive and as a latent threat. However, the inherent capabilities of these nanopolymers to kill bacteria have been largely overlooked. Here, we report that Pluronic shaped as superstructures (self-organized array of micelles) in fact possess a broad-spectrum bactericidal activity (capability of killing bacteria) similar to that shown for some antibiotics. This further represents the first report that shows that appropriate control of superstructured mesophase architecture is a key parameter for bactericidal efficacy. Based on this finding, we have developed a highly bactericidal coating (>99.9% kill) against all tested Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Salmonella typhimurium LT2, Escherichia coli K12 and Pseudomonas aeruginosa PAO1) bacteria which moreover allows the adhesion and proliferation of mammalian cells. The inexpensiveness and ease of production make these versatile nanopolymer structures a powerful tool for the development of a new generation of highly effective antimicrobial coatings.

Drug-Loaded Biocompatible Nanocarriers Embedded in Poloxamer 407 Hydrogels as Therapeutic Formulations

Hydrogels are three-dimensional networks of hydrophilic polymers able to absorb and retain a considerable amount of water or biological fluid while maintaining their structure. Among these, thermo-sensitive hydrogels, characterized by a temperature-dependent sol–gel transition, have been massively used as drug delivery systems for the controlled release of various bioactives. Poloxamer 407 (P407) is an ABA-type triblock copolymer with a center block of hydrophobic polypropylene oxide (PPO) between two hydrophilic polyethyleneoxide (PEO) lateral chains. Due to its unique thermo-reversible gelation properties, P407 has been widely investigated as a temperature-responsive material. The gelation phenomenon of P407 aqueous solutions is reversible and characterized by a sol–gel transition temperature. The nanoencapsulation of drugs within biocompatible delivery systems dispersed in P407 hydrogels is a strategy used to increase the local residence time of various bioactives at the injection site. In this mini-review, the state of the art of the most important mixed systems made up of colloidal carriers localized within a P407 hydrogel will be provided in order to illustrate the possibility of obtaining a controlled release of the entrapped drugs and an increase in their therapeutic efficacy as a function of the biomaterial used.

A Novel Thermoresponsive Gel as a Potential Delivery System for Lipoxin

The objective of this study was to evaluate a novel thermoresponsive polyisocyanopeptide (PIC)–based hydrogel as an injectable carrier for local drug delivery for periodontal applications. Three formulations of PIC gels, 0.2%, 0.5%, and 1% w/w, were prepared. As controls, commercially available poloxamer 407 (P407) gels of 20% and 26% w/w were used. Lipoxin A₄ (LXA₄), a proresolving drug, was suspended into the gel solutions. The systems were evaluated regarding dynamic mechanical properties, injectability and stability, release and bioactivity of LXA₄, and cytocompatibility. Results showed that the gelation temperatures of PIC and P407 gels were around 13°C to 23°C. PIC gels were less viscous and mechanically weaker than P407 gels due to the low polymer concentrations. However, PIC gels kept gel integrity for at least 2 wk when incubated with phosphate-buffered saline, whereas P407 gels were disintegrated totally within 1 wk. LXA₄ was chemically stable in both neutral and alkaline medium for over 1 mo. The release of LXA₄ from either 1% PIC or 26% P407 gels depicted an initial burst release followed by a sustained release for around 4 d. The extent of burst release was negatively correlated to the polymer concentration. LXA₄ remained bioactive after release from PIC gels. No cytotoxicity was observed for 1% PIC gel. However, 26% P407 inhibited periodontal ligament cell and gingival epithelial cell growth. In conclusion, the thermoresponsive PIC gel is a potential candidate for periodontal drug delivery.

Mucosal Applications of Poloxamer 407-Based Hydrogels: An Overview

Poloxamer 407, also known by the trademark Pluronic^® F127, is a water-soluble, non-ionic triblock copolymer that is made up of a hydrophobic residue of polyoxypropylene (POP) between the two hydrophilic units of polyoxyethylene (POE). Poloxamer 407-based hydrogels exhibit an interesting reversible thermal characteristic. That is, they are liquid at room temperature, but they assume a gel form when administered at body temperature, which makes them attractive candidates as pharmaceutical drug carriers. These systems have been widely investigated in the development of mucoadhesive formulations because they do not irritate the mucosal membranes. Based on these mucoadhesive properties, a simple administration into a specific compartment should maintain the required drug concentration in situ for a prolonged period of time, decreasing the necessary dosages and side effects. Their main limitations are their modest mechanical strength and, notwithstanding their bioadhesive properties, their tendency to succumb to rapid elimination in physiological media. Various technological approaches have been investigated in the attempt to modulate these properties. This review focuses on the application of poloxamer 407-based hydrogels for mucosal drug delivery with particular attention being paid to the latest published works.

Synthesis of Zwitterionic Pluronic Analogs

Novel polymer amphiphiles with chemical structures designed as zwitterionic analogs of Pluronic block copolymers were prepared by controlled free radical polymerization of phosphorylcholine (PC) or choline phosphate (CP) methacrylate monomers from a difunctional poly(propylene oxide) (PPO) macroinitiator. Well-defined, water-dispersible zwitterionic triblock copolymers, or "zwitteronics", were prepared with PC content ranging from 5 to 47 mol percent and composition-independent surfactant characteristics in water, which deviate from the properties of conventional Pluronic amphiphiles. These PC-zwitteronics assembled into nanoparticles in water, with tunable sizes and critical aggregation concentrations (CACs) based on their hydrophilic-lipophilic balance (HLB). Owing to the lower critical solution temperature (LCST) miscibility of the hydrophobic PPO block in water, PC-zwitteronics exhibited thermoreversible aqueous solubility tuned by block copolymer composition. The chemical versatility of this approach was demonstrated by embedding functionality, in the form of alkyne groups, directly into the zwitterion moieties. These alkynes proved ideal for cross-linking the zwitteronic nanoparticles and for generating nanoparticle-cross-linked hydrogels using UV-initiated thiol-yne "click" chemistry.

In Vitro ADME Properties of Two Novel Antimicrobial Peptoid-Based Compounds as Potential Agents against Canine Pyoderma

Antimicrobial peptides (AMPs) hold promise as the next generation of antimicrobial agents, but often suffer from rapid degradation in vivo. Modifying AMPs with non-proteinogenic residues such as peptoids (oligomers of N-alkylglycines) provides the potential to improve stability. We have identified two novel peptoid-based compounds, B1 and D2, which are effective against the canine skin pathogen Staphylococcus pseudintermedius, the main cause of antibiotic use in companion animals. We report on their potential to treat infections topically by characterizing their release from formulation and in vitro ADME properties. In vitro ADME assays included skin penetration profiles, stability to proteases and liver microsomes, and plasma protein binding. Both B1 and D2 were resistant to proteases and >98% bound to plasma proteins. While half-lives in liver microsomes for both were >2 h, peptoid D2 showed higher stability to plasma proteases than the peptide-peptoid hybrid B1 (>2 versus 0.5 h). Both compounds were suitable for administration in an oil-in-water cream formulation (50% release in 8 h), and displayed no skin permeation, in the absence or presence of skin permeability modifiers. Our results indicate that these peptoid-based drugs may be suitable as antimicrobials for local treatment of canine superficial pyoderma and that they can overcome the inherent limitations of stability encountered in peptides.

Development and characterisation of levosulpiride-loaded suppositories with improved bioavailability in vivo

The purpose of this study was to develop and characterize levosulpiride loaded liquid suppository with improved bioavailability. The content of levosulpiride-loaded liquid suppositories were optimized in a series of experiments using various weight ratios of P188, P407, Tween 80, and drug. The suppositories were liquid at room temperature, however, when rectally administered, they became gel at body temperature. Their rheological properties and release characteristics were determined in vitro while pharmacokinetic study was performed after its rectal administration in rats and compared with drug suspension. Poloxamer 188 and Twee 80 decreased the gelation temperature and gelation time, but increased the gel strength and mucoadhesive force of liquid suppositories. Liquid suppository composed of [Levosulpiride/P 188/P 407/Tween 80 (1/15/17/3%)] with a gelation temperature of about 30.7 °C remained liquid at 25 °C, but converted to gel at 30-36.5 °C, resulting in easy administration and rapid gelation inside the body. This liquid suppository gave a considerably increased dissolution rate reflected in a meaningfully higher plasma concentration and 7.1-fold AUC values of levosulpiride in rats as compared to the drug suspension. Hence, liquid suppository system could be used for enhanced bioavailability of levosulpiride-loaded pharmaceutical products.

Pharmacokinetics of butorphanol tartrate in a long-acting poloxamer 407 gel formulation administered to Hispaniolan Amazon parrots (Amazona ventralis)

OBJECTIVE To determine pharmacokinetics of butorphanol tartrate incorporated into poloxamer 407 (P407) after SC administration to Hispaniolan Amazon parrots (Amazona ventralis). ANIMALS 11 adult Hispaniolan Amazon parrots (6 males and 5 females; 11 to 27 years old). PROCEDURES A sterile formulation of butorphanol in P407 (But-P407) 25% (percentage determined as [weight of P407/weight of diluent] × 100]) was created (8.3 mg/mL). Five preliminary experiments (2 birds/experiment) were performed to determine the ideal dose for this species. The formulation then was administered (12.5 mg/kg, SC) to 8 birds. Blood samples were collected before (time 0) and 0.08, 0.5, 1, 2, 4, 8, 12, and 24 hours after drug administration. Some birds were used more than once, with a washout period of ≥ 3 months between subsequent treatments. Butorphanol concentrations were quantitated by use of liquid chromatography-tandem mass spectrometry. Pharmacokinetic analysis was performed by use of noncompartmental analysis. RESULTS Maximal plasma butorphanol concentration was reached at 1.31 hours. Plasma concentrations of butorphanol remained > 100 ng/mL for > 3 hours (all birds) or > 4 hours (5/8 birds) but < 8 hours (all birds). Half-life of the terminal slope was 3.41 hours. No adverse effects were detected. CONCLUSIONS AND CLINICAL RELEVANCE Butorphanol was absorbed well from the But-P407 25% by Hispaniolan Amazon parrots, and absorption followed a pharmacokinetic profile compatible with a sustained-release drug. A dose of 12.5 mg/kg, SC, would theoretically provide analgesia for 4 to 8 hours. No adverse effects were detected. Studies on the pharmacodynamics of this formulation are necessary to confirm the degree and duration of analgesia.

Hyaluronic Acid-Based Hydrogel Coating Does Not Affect Bone Apposition at the Implant Surface in a Rabbit Model

BACKGROUND

Uncemented orthopaedic implants rely on the bone-implant interface to provide stability, therefore it is essential that a coating does not interfere with the bone-forming processes occurring at the implant interface. In addition, local application of high concentrations of antibiotics for prophylaxis or treatment of infection may be toxic for osteoblasts and could impair bone growth.

QUESTIONS/PURPOSES

In this animal study, we investigated the effect of a commercially available hydrogel, either unloaded or loaded with 2% vancomycin. We asked, does unloaded hydrogel or hydrogel with vancomycin (1) interfere with bone apposition and timing of bone deposition near the implant surface; and (2) induce a local or systemic inflammatory reaction as determined by inflammation around the implant and hematologic parameters.

METHODS

In 18 New Zealand White rabbits, an uncoated titanium rod (n = 6), a rod coated with unloaded hydrogel (n = 6), or a rod coated with 2% vancomycin-loaded hydrogel (n = 6) was implanted in the intramedullary canal of the left tibia. After 28 days, the bone volume fraction near the implant was measured with microCT analysis, inflammation was semiquantitatively scored on histologic sections, and timing of bone apposition was followed by semiquantitative scoring of fluorochrome incorporation on histologic sections. Two observers, blinded to the treatment, scored the sections and reconciled their scores if there was a disagreement. The hematologic inflammatory reaction was analyzed by measuring total and differential leukocyte counts and erythrocyte sedimentation rates in blood. With group sizes of six animals per group, we had 79% power to detect a difference of 25% in histologic scoring for infection and inflammation.

RESULTS

No differences were found in the amount of bone apposition near the implant in the No Gel group (48.65% ± 14.95%) compared with the Gel group (59.97% ± 5.02%; mean difference [MD], 11.32%; 95% CI, -3.89% to 26.53%; p = 0.16) or for the Van2 group (56.12% ± 10.06%; MD, 7.46; 95% CI, -7.75 to 22.67; p = 0.40), with the numbers available. In addition, the scores for timing of bone apposition did not differ between the No Gel group (0.50 ± 0.55) compared with the Gel group (0.33 ± 0.52; MD, -0.17; 95% CI, -0.86 to 0.53; p = 0.78) or the Van2 group (0.83 ± 0.41; MD, 0.33; 95% CI, -0.36 to 1.03; p = 0.42). Furthermore, we detected no differences in the histopathology scores for inflammation in the No Gel group (2.33 ± 1.67) compared with the Gel group (3.17 ± 1.59; MD, 0.83; 95% CI, -0.59 to 2.26; p = 0.31) or to the Van2 group (2.5 ± 1.24; MD, 0.17; 95% CI, -1.26 to 1.59; p = 0.95). Moreover, no differences in total leukocyte count, erythrocyte sedimentation rate, and neutrophil, monocyte, eosinophil, basophil, and lymphocyte counts were present between the No Gel or Van2 groups compared with the Gel control group, with the numbers available.

CONCLUSION

The hydrogel coated on titanium implants, unloaded or loaded with 2% vancomycin, had no effect on the volume or timing of bone apposition near the implant, and did not induce an inflammatory reaction in vivo, with the numbers available.

CLINICAL RELEVANCE

Antibiotic-loaded hydrogel may prove to be a valuable option to protect orthopaedic implants from bacterial colonization. Future clinical safety studies will need to provide more evidence that this product does not impair bone formation near the implant and prove the safety of this product.

Smart polymers in drug delivery: a biological perspective

Key to the widespread application of smart polymers in drug delivery is understanding the mechanistic interplay, as well as consequence, of the presence of these macromolecules within living systems.

Injectable gentamicin-loaded thermo-responsive hyaluronic acid derivative prevents infection in a rabbit model

Despite the use of systemic antibiotic prophylaxis, the surgical fixation of open fractures with osteosynthesis implants is associated with high infection rates. Antibiotic-loaded biomaterials (ALBs) are increasingly used in implant surgeries across medical specialties to deliver high concentrations of antibiotics to the surgical site and reduce the risk of implant-associated infection. ALBs which are either less or not restricted in terms of spatial distribution and which may be applied throughout complex wounds could offer improved protection against infection in open fracture care. A thermo-responsive hyaluronic acid derivative (hyaluronic acid-poly(N-isopropylacrylamide) (HApN)) was prepared by a direct amidation reaction between the tetrabutyl ammonium (TBA) salt of hyaluronic acid and amine-terminated poly(N-isopropylacrylamide) (pN). The degree of grafting, and gelation properties of this gel were characterized, and the composition was loaded with gentamicin. The rheological- and release properties of this gentamicin-loaded HApN composition were tested in vitro and its efficacy in preventing infection was tested in a rabbit model of osteosynthesis contaminated with Staphylococcus aureus. The gentamicin-loaded HApN composition was able to prevent bacterial colonization of the implant site as shown by quantitative bacteriology. This finding was supported by histopathological evaluation of the humeri samples where no bacteria were found in the stained sections. In conclusion, this gentamicin-loaded HApN hydrogel effectively prevents infection in a complex wound, simulating a contaminated fracture treated with plating osteosynthesis.

STATEMENT OF SIGNIFICANCE

Fracture fixation after trauma is associated with high infection rates. Antibiotic loaded biomaterials (ALBs) can provide high local concentrations without systemic side effects. However, the currently available ALBs have limited accessibility to contaminated tissues in open fractures because of predetermined shape. Thus, a novel thermo-responsive hyaluronan based hydrogel with control over gelation temperature is reported. The efficacy of this gentamicin loaded hyaluronan derivative is demonstrated in an in vivo fracture model in the presence of fracture fixation hardware. The bacterial burden is cleared in all of the inoculated rabbits in the presence of the ALB. Thus, the proposed injectable thermo-responsive hyaluronan presents an effective ALB for the prevention of infection.

Injectable thermosensitive gelling delivery system for the sustained release of lidocaine. Ther Deliv. 2016;7:359-368. [PMID: 27250538 DOI: 10.4155/tde-2016-0014]

BACKGROUND

Patients undergoing arthroplasty require appropriate postsurgical pain relief. Analgesia is typically achieved through bolus doses of short-acting local anesthetics and with oral analgesics such as opiates, which are associated with systemic side effects. By formulating an injectable thermosensitive gelling system containing lidocaine, sustained and local delivery can be achieved following a single administration.

RESULTS

Poloxamer-based thermosensitive gelling formulations were prepared. Altering the weight ratios of poloxamers affected the sol-to-gel transition temperature, mechanical and rheological properties and in vitro drug release. Desirable formulations gelled between 28 and 33°C providing sustained release of lidocaine over 48 h.

CONCLUSION

Thermosensitive gelling systems are promising for sustained drug release following patient administration and may be beneficial in addressing postoperative pain.