Dendritic Nanogels Directed Dual-Encapsulation Topical Delivery System of Antimicrobial Peptides Targeting Skin Infections

Antimicrobial peptides (AMPs) are promising antibacterial agents in the fight against multidrug resistant pathogens. However, their application to skin infections is limited by the absence of a realizable topical delivery strategy. Herein, a hybrid hierarchical delivery system for topical delivery of AMPs is accomplished through the incorporation of AMPs into dendritic nanogels (DNGs) and their subsequent embedding into poloxamer gel. The high level of control over the crosslink density and the number of chosen functionalities makes DNGs ideal capsules with tunable loading capacity for DPK-060, a human kininogen-derived AMP. Once embedded into the poloxamer gel, DPK-060 encapsulated in DNGs displays a slower release rate compared to those entrapped directly in the gels. In vitro EpiDerm Skin Irritation Tests show good biocompatibility, while MIC and time-kill curves reveal the potency of the peptide toward Staphylococcus aureus. Anti-infection tests on ex vivo pig skin and in vivo mouse infection models demonstrate that formulations with 0.5% and 1% AMPs significantly inhibit the growth of S. aureus. Similar outcomes are observed for an in vivo mouse surgical site infection model. Importantly, when normalizing the bacteria inhibition to released/free DPK-060 at the wound site, all formulations display superior efficacy compared to DPK-060 in solution.

Levofloxacin in nanostructured lipid carriers: Preformulation and critical process parameters for a highly incorporated formulation

The first step of a successful nanoformulation development is preformulation studies, in which the best excipients, drug-excipient compatibility and interactions can be identified. During the formulation, the critical process parameters and their impact must be studied to establish the stable system with a high drug entrapment efficiency (EE). This work followed these steps to develop nanostructured lipid carriers (NLCs) to deliver the antibiotic levofloxacin (LV). The preformulation studies covered drug solubility in excipients and thorough characterization using thermal analysis, X-ray diffraction and spectroscopy. A design of experiment based on the process parameters identified nanoparticles with < 200 nm in size, polydispersity <= 0.3, zeta potential -21 to -24 mV, high EE formulations (>71 %) and an acceptable level of LV degradation products (0.37-1.13 %). To the best of our knowledge, this is the first time that a drug degradation is reported and studied in work on nanostructured lipids. LV impurities following the NLC production were detected, mainly levofloxacin N-oxide, a degradation product that has no antimicrobial activity and could interfere with LV quantification in spectrophotometric experiments. Also, the achievement of the highest EE in lipid nanoparticles than those described in the literature to date and the apparent protective action of NLC of entrapped-LV against degradation are important findings.

Understanding the Thermodynamic Mechanisms Leading to the Binding of Albumin to Lipid Nanocapsules

Lipid nanocapsules (LNCs) are drug delivery platforms designed for different administration routes including intravenous delivery. Nanocarrier binding with plasma proteins such as albumin is an important factor that influences the pharmacokinetics of the drug and the drug delivery system. The aim of this paper was to characterize LNCs with different surface compositions and hydrophobicities to study their interactions with albumin: binary LNCs [oil-glyceryl trioctanoate (TG) and PEGylated surfactant macrogol 15-hydroxystearate (MHS)] and ternary LNCs (TG, MHS, and Span 80). Span was found to stabilize and decrease the LNC size. The formation of a stable LNC/albumin complex in the ground state was demonstrated. Thermodynamic parameters indicated that complex formation was exothermic and spontaneous, and the interactions involved van der Waals forces and hydrogen bond formation. Ternary LNCs showed higher affinity for albumin than did binary LNCs (affinity constant 10-fold higher). This study is the first report on the thermodynamic mechanisms that lead to the formation of a complex between albumin and organic nanoparticles with different surface architectures.

Anticrystal Engineering of Ketoprofen and Ester Local Anesthetics: Ionic Liquids or Deep Eutectic Mixtures?

Ionic liquids (ILs) and deep eutectic mixtures (DEMs) are potential solutions to the problems of low solubility, polymorphism, and low bioavailability of drugs. The aim of this work was to develop and investigate ketoprofen (KET)-based ILs/DEMs containing an ester local anesthetic (LA): benzocaine (BEN), procaine (PRO) and tetracaine (TET) as the second component. ILs/DEMs were prepared via a mechanosynthetic process that involved the mixing of KET with an LA in a range of molar ratios and applying a thermal treatment. After heating above the melting point and quench cooling, the formation of supercooled liquids with Tgs that were dependent on the composition was observed for all KET-LA mixtures with exception of that containing 95 mol% of BEN. The KET-LA mixtures containing either ≥ 60 mol% BEN or 95 mol% of TET showed crystallization to BEN and TET, respectively, during either cooling or second heating. KET decreased the crystallization tendency of BEN and TET and increased their glass-forming ability. The KET-PRO systems showed good glass-forming ability and did not crystallize either during the cooling or during the second heating cycle irrespective of the composition. Infrared spectroscopy and molecular modeling indicated that KET and LAs formed DEMs, but in the KET-PRO systems small quantities of carboxylate anions were present.

A comparison of different strategies for antimicrobial peptides incorporation onto/into lipid nanocapsules

Aim: Over the last decade, antimicrobial peptides (AMPs) have emerged as a promising alternative for the treatment of various infections. The aim of this work is to explore the potential of lipid nanocapsules for the delivery of AMPs. Three approaches were compared in terms of encapsulation efficiency, peptide activity and protection against proteases: peptide encapsulation, surface adsorption or covalent attachment of three selected AMPs. Results: A potentiation of the antimicrobial activity and a partial protection of the peptides after adsorption were demonstrated compared with native peptides. Conversely, encapsulation allowed better peptide stability, correlated with higher encapsulation efficiencies and a preservation of the activity. Finally, the covalent attachment strategy turned out to be less conclusive due to peptide inactivation. Conclusion: In brief, a lipid nanocapsule-based platform appears suitable to deliver AMPs.

Characterization of the in vitro, ex vivo, and in vivo Efficacy of the Antimicrobial Peptide DPK-060 Used for Topical Treatment

Antimicrobial peptides, also known as host defense peptides, have recently emerged as a promising new category of therapeutic agents for the treatment of infectious diseases. This study evaluated the preclinical in vitro, ex vivo, and in vivo antimicrobial activity, as well as the potential to cause skin irritation, of human kininogen-derived antimicrobial peptide DPK-060 in different formulations designed for topical delivery. We found that DPK-060 formulated in acetate buffer or poloxamer gel caused a marked reduction of bacterial counts of Staphylococcus aureus in vitro (minimum microbicidal concentration <5 μg/ml). We also found that DPK-060 in poloxamer gel significantly suppressed microbial survival in an ex vivo wound infection model using pig skin and in an in vivo mouse model of surgical site infection (≥99 or ≥94% reduction in bacterial counts was achieved with 1% DPK-060 at 4 h post-treatment, respectively). Encapsulation of DPK-060 in different types of lipid nanocapsules or cubosomes did not improve the bactericidal potential of the peptide under the applied test conditions. No reduction in cell viability was observed in response to administration of DPK-060 in any of the formulations tested. In conclusion, the present study confirms that DPK-060 has the potential to be an effective and safe drug candidate for the topical treatment of microbial infections; however, adsorption of the peptide to nanocarriers failed to show any additional benefits.

Antimicrobial synergy of monolaurin lipid nanocapsules with adsorbed antimicrobial peptides against Staphylococcus aureus biofilms in vitro is absent in vivo

Bacterial infections are mostly due to bacteria in their biofilm-mode of growth, while penetrability of antimicrobials into infectious biofilms and increasing antibiotic resistance hamper infection treatment. In-vitro, monolaurin lipid nanocapsules (ML-LNCs) carrying adsorbed antimicrobial peptides (AMPs) displayed synergistic efficacy against planktonic Staphylococcus aureus, but it has not been demonstrated, neither in-vitro nor in-vivo, that such ML-LNCs penetrate into infectious S. aureus biofilms and maintain synergy with AMPs. This study investigates the release mechanism of AMPs from ML-LNCs and possible antimicrobial synergy of ML-LNCs with the AMPs DPK-060 and LL-37 against S. aureus biofilms in-vitro and in a therapeutic, murine, infected wound-healing model. Zeta potentials demonstrated that AMP release from ML-LNCs was controlled by the AMP concentration in suspension. Both AMPs demonstrated no antimicrobial efficacy against four staphylococcal strains in a planktonic mode, while a checkerboard assay showed synergistic antimicrobial efficacy when ML-LNCs and DPK-060 were combined, but not for combinations of ML-LNCs and LL-37. Similar effects were seen for growth reduction of staphylococcal biofilms, with antimicrobial synergy persisting only for ML-LNCs at the highest level of DPK-060 or LL-37 adsorption. Healing of wounds infected with bioluminescent S. aureus Xen36, treated with ML-LNCs alone, was faster when treated with PBS, while AMPs alone did not yield faster wound-healing than PBS. Faster, synergistic wound-healing due to ML-LNCs with adsorbed DPK-060, was absent in-vivo. Summarizing, antimicrobial synergy of ML-LNCs with adsorbed antimicrobial peptides as seen in-vitro, is absent in in-vivo healing of infected wounds, likely because host AMPs adapted the synergistic role of the AMPs added. Thus, conclusions regarding synergistic antimicrobial efficacy, should not be drawn from planktonic data, while even in-vitro biofilm data bear little relevance for the in-vivo situation.

Reverse micelle-lipid nanocapsules: a novel strategy for drug delivery of the plectasin derivate AP138 antimicrobial peptide

Introduction

Resistance to traditional antibiotics is an increasingly serious problem. Antimicrobial peptides (AMPs) have emerged as a new therapeutic class with great potential against infectious diseases, as they are less prone to induce resistance. Nanotechnology-based delivery strategies can improve the efficiency and stability of AMPs, particularly against proteolytic degradation. Lipid nanocapsules (LNCs) are a new generation of biomimetic nanocarriers and were used in this study to deliver peptides.

Methods

AMP-loaded reverse micelles (RM) were developed and incorpo rated into LNCs by the phase inversion process and the antimicrobial activity of the AMPs-loaded LNC was evaluated by the minimum inhibitory concentration method. We studied the activity of AMP solutions and AMP-loaded LNCs against Gram-positive and Gram-negative bacterial strains and then evaluated the encapsulation of a new cationic AMP called AP138. Finally, we analyzed the effect of enzymatic attack on AP138 and AP138-RM-LNCs after incubation with trypsin.

Results

AP138 was efficiently encapsulated in the LNCs (encapsulation efficiency = 97.8% at a drug loading of 0.151%), resulting in protection against degradation by proteases and the preservation of antimicrobial activity against Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus.

Conclusion

This study shows that RM-LNCs are an excellent candidate system to deliver AMPs.

Polymeric Nanoparticles for Increasing Oral Bioavailability of Curcumin

Despite the promising biological and antioxidant properties of curcumin, its medical applications are limited due to poor solubility in water and low bioavailability. Polymeric nanoparticles (NPs) adapted to oral delivery may overcome these drawbacks. Properties such as particle size, zeta potential, morphology and encapsulation efficiency were assessed. Then, the possibility of storing these NPs in a solid-state form obtained by freeze-drying, in vitro curcumin dissolution and cytocompatibility towards intestinal cells were evaluated. Curcumin-loaded Eudragit^® RLPO (ERL) NPs showed smaller particle diameters (245 ± 2 nm) and better redispersibility after freeze-drying than either poly(lactic-co-glycolic acid) (PLGA) or polycaprolactone (PCL) NPs. The former NPs showed lower curcumin encapsulation efficiency (62%) than either PLGA or PCL NPs (90% and 99%, respectively). Nevertheless, ERL NPs showed rapid curcumin release with 91 ± 5% released over 1 h. The three curcumin-loaded NPs proposed in this work were also compatible with intestinal cells. Overall, ERL NPs are the most promising vehicles for increasing the oral bioavailability of curcumin.

Freeze-dried and re-hydrated liquid crystalline nanoparticles stabilized with disaccharides for drug-delivery of the plectasin derivative AP114 antimicrobial peptide

Liquid crystalline nanoparticles (LCNPs), e.g. cubosomes and hexosomes, are receiving more and more attraction as drug delivery vehicles. Dry powder formulation that forms LCNPs upon hydration can be advantageous to make new routes of administration accessible. In this work, we investigate use of three disaccharides (lactose, trehalose and sucrose) as protective matrices for glycerol monooleate based LCNP forming powders produced by freeze-drying. Phase behavior, particle size and size distributions at the different preparation steps were monitored by small angle x-ray scattering (SAXS) and dynamic light scattering (DLS). Particle appearance was imaged by cryogenic transmission electron microscopy (cryo-TEM). Moreover, the therapeutic relevant antimicrobial peptide AP114 (plectasin derivative) was incorporated in the formulations. Peptide encapsulation and release as well as in vitro antibacterial effect were investigated. Results showed that all freeze-dried powders did form particles with liquid crystalline structure upon hydration. However, a phase transition from the bicontinuous cubic Pn3m to the reversed hexagonal was observed, as a consequence of sugar addition and the freeze-drying procedure. Data indicates that trehalose is the preferred choice of lyo-protectant in order to maintain a mono-modal particle size distribution. In addition, antimicrobial activity of AP114-containing formulations was found to be highest for the formulation containing trehalose. The release kinetics of AP114 from the nanoparticles was strongly affected by the dimensions of the hexagonal phase. Larger dimension of the hexagonal phase, significantly improved the release of AP114 and antimicrobial activity of the formulation.

Antibacterial activity of antipsychotic agents, their association with lipid nanocapsules and its impact on the properties of the nanocarriers and on antibacterial activity

Bacterial antibiotic resistance is an emerging public health problem worldwide; therefore, new therapeutic strategies are needed. Many studies have described antipsychotic compounds that present antibacterial activity. Hence, the aims of this study were to evaluate the in vitro antibacterial activity of antipsychotics belonging to different chemical families, to assess the influence of their association with lipid nanocapsules (LNCs) on their antimicrobial activity as well as drug release and to study the uptake of LNCs by bacterial cells. Antibacterial activity was evaluated against Gram-positive Staphylococcus aureus and Gram negative Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii by minimum inhibitory concentration (MIC) assay, and the capability of killing tested microorganisms was evaluated by time kill assay. LNCs were prepared by phase inversion method, and the antipsychotic agents were incorporated using pre-loading and post-loading strategies. Only phenothiazines and thioxanthenes showed antibacterial activity, which was independent of antibiotic-resistance patterns. Loading the nanocarriers with the drugs affected the properties of the former, particularly their zeta potential. The release rate depended on the drug and its concentration-a maximum of released drug of less than 40% over 24 hours was observed for promazine. The influence of the drug associations on the antibacterial properties was concentration-dependent since, at low concentrations (high nanocarrier/drug ratio), the activity was lost, probably due to the high affinity of the drug to nanocarriers and slow release rate, whereas at higher concentrations, the activity was well maintained for the majority of the drugs. Chlorpromazine and thioridazine increased the uptake of the LNCs by bacteria compared with blank LNCs, even below the minimum inhibitory concentration.

Surface active properties of lipid nanocapsules

Lipid nanocapsules (LNCs) are biomimetic nanocarriers used for the encapsulation of a broad variety of active ingredients. Similar to surface active compounds, LNCs contain both hydrophilic and hydrophobic parts in their structure. Moreover, the components of LNCs, macrogol 15 hydroxystearate (MHS) and lecithin, are known for their surface active properties. Therefore, the aim of this paper was to investigate the capability of the LNCs to decrease surface tension using two techniques: drop tensiometry and the Wilhelmy plate method. LNCs with diameters ranging from 30 to 100 nm were successfully obtained using a phase inversion technique. The LNCs' properties, such as size and zeta potential, depend on the composition. LNCs exhibit a lower limiting surface tension compared to MHS (34.8-35.0 mN/m and 37.7-38.8 mN/m, respectively), as confirmed by both drop tensiometry and the Wilhelmy plate method. LNCs have exhibited a saturated interfacial concentration (SIC) that was 10-fold higher than the critical micellar concentration (CMC) of MHS or the SIC of binary and ternary mixtures of LNC ingredients. The SIC of the LNC formulations depended on the mass mixing ratio of the MHS/triglycerides but not on the presence of lecithin. The CMC/SIC values measured by the Wilhelmy plate method were higher than those obtained using drop tensiometry because of the longer duration of the tensiometry measurement. In conclusion, the surfactant-like properties of the LNCs offer new possibilities for medical and pharmaceutical applications.

Synergistic interactions between antimicrobial peptides derived from plectasin and lipid nanocapsules containing monolaurin as a cosurfactant against Staphylococcus aureus

Development of effective antibacterial agents for the treatment of infections caused by Gram-positive bacteria resistant to existing antibiotics, such as methicillin-resistant Staphylococcus aureus (MRSA), is an area of intensive research. In this work, the antibacterial efficacy of two antimicrobial peptides derived from plectasin, AP114 and AP138, used alone and in combination with monolaurin-lipid nanocapsules (ML-LNCs) was evaluated. Several interesting findings emerged from the present study. First, ML-LNCs and both plectasin derivatives showed potent activity against all 14 tested strains of S. aureus, independent of their resistance phenotype. Both peptides displayed a considerable adsorption (33%-62%) onto ML-LNCs without having an important impact on the particle properties such as size. The combinations of peptide with ML-LNC displayed synergistic effect against S. aureus, as confirmed by two methods: checkerboard and time-kill assays. This synergistic interaction enables a dose reduction and consequently decreases the risk of toxicity and has the potential of minimizing the development of resistance. Together, these results suggest that ML-LNCs loaded with a plectasin derivative may be a very promising drug delivery system for further development as a novel antibacterial agent against S. aureus, including MRSA.

Amorphous Polymeric Drug Salts as Ionic Solid Dispersion Forms of Ciprofloxacin

Ciprofloxacin (CIP) is a poorly soluble drug that also displays poor permeability. Attempts to improve the solubility of this drug to date have largely focused on the formation of crystalline salts and metal complexes. The aim of this study was to prepare amorphous solid dispersions (ASDs) by ball milling CIP with various polymers. Following examination of their solid state characteristics and physical stability, the solubility advantage of these ASDs was studied, and their permeability was investigated via parallel artificial membrane permeability assay (PAMPA). Finally, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the ASDs were compared to those of CIP. It was discovered that acidic polymers, such as Eudragit L100, Eudragit L100-55, Carbopol, and HPMCAS, were necessary for the amorphization of CIP. In each case, the positively charged secondary amine of CIP was found to interact with carboxylate groups in the polymers, forming amorphous polymeric drug salts. Although the ASDs began to crystallize within days under accelerated stability conditions, they remained fully X-ray amorphous following exposure to 90% RH at 25 °C, and demonstrated higher than predicted glass transition temperatures. The solubility of CIP in water and simulated intestinal fluid was also increased by all of the ASDs studied. Unlike a number of other solubility enhancing formulations, the ASDs did not decrease the permeability of the drug. Similarly, no decrease in antibiotic efficacy was observed, and significant improvements in the MIC and MBC of CIP were obtained with ASDs containing HPMCAS-LG and HPMCAS-MG. Therefore, ASDs may be a viable alternative for formulating CIP with improved solubility, bioavailability, and antimicrobial activity.

Cubosomes post-loaded with antimicrobial peptides: characterization, bactericidal effect and proteolytic stability

Novel antibiotics, such as antimicrobial peptides (AMPs), have recently attended more and more attraction. In this work, dispersed cubic liquid crystalline gel (cubosomes) was used as drug delivery vehicles for three AMPs (AP114, DPK-060 and LL-37). Association of peptides onto cubosomes was studied at two cubosome/peptide ratios using high performance liquid chromatography, ζ-potential and circular dichroism measurements. AMPs impact on the cubosome structure was investigated using small angle x-ray scattering and cryogenic transmission electron microscopy. The antimicrobial effect of the AMP loaded cubosomes was studied in vitro by minimum inhibitory concentration and time-kill assays. Proteolytic protection was investigated by incubating the formulations with two elastases and the antimicrobial effect after proteolysis was studied using radial diffusion assay. Different association efficacy onto the cubosomes was observed among the AMPs, with LL-37 showing greatest association (>60%). AP114 loaded cubosomes displayed a preserved antimicrobial effect, whereas for LL-37 the broad spectrum bacterial killing was reduced to only comprise Gram-negative bacteria. Interestingly, DPK-060 loaded cubosomes showed a slight enhanced effect against S. aureus and E. coli strains. Moreover, the cubosomes were found to protect LL-37 from proteolytic degradation, resulting in a significantly better bactericidal effect after being subjected to elastase, compared to unformulated peptide.

Design of chondroitin sulfate-based polyelectrolyte nanoplexes: Formation of nanocarriers with chitosan and a case study of salmon calcitonin

The aim of this work was to examine the formation and properties of chondroitin sulfate (CHON)-based nanoparticles (NPs), namely CHON/chitosan (CHIT), CHON/CHIT/calcitonin (sCT) and CHON/sCT. Both, positively and negatively charged CHON/CHIT NPs have been successfully obtained with properties that were dependent on the polymer mixing ratio, polymer concentration and molecular weight of CHIT. sCT was successfully loaded into CHON/CHIT NPs with efficiency close to 100% and notably high loading (up to 33%). A new type of NPs composed of CHON and sCT (a binary system) has been successfully developed. CHON/sCT NPs offer the advantage of a very high drug loading up to 73%. The particle size of CHON-based NPs increased in PBS, acetate buffer and in HCl solution compared to that in water, but most of them remained in the nano-range even after 24h. The media and composition of the nanocarriers were found to affect the release of sCT.

Antibacterial action of lipid nanocapsules containing fatty acids or monoglycerides as co-surfactants

Lipid nanocapsules (LNCs) are a new generation of biomimetic nanocarriers obtained via a phase inversion temperature method and have an oily core of medium-chain triglycerides that is surrounded by a shelf containing a lipophilic surfactant (lecithin) and a hydrophilic surfactant macrogol 15-hydroxystearate. The aim of the present study was to produce LNCs with antibacterial activity by replacing lecithin with other lipophilic surface active compounds, namely medium-chain fatty acids and their 1-monoglycerides, which are known to have antimicrobial properties. Fatty acids and monoglycerides were found to affect the properties of LNCs, such as particle size and zeta potential. Incorporation of a co-surfactant decreased significantly particle size (p⩽0.0039). Furthermore, incorporation of either lecithin or fatty acids with at least 10 carbon atoms yielded LNCs with the zeta potential significantly more negative than that of LNCs composed solely of triglycerides and macrogol 15 hydroxystearate (p⩽0.0310). Moreover, they were capable of decreasing the phase inversion temperature. The activity of the LCNs against Gram-positive S. aureus, including a methicillin-resistant strain, increased with increases in the length of the hydrocarbon tail. Monoglyceride-LNCs were found to be more active than the corresponding fatty acids. The opposite behaviour was observed for Gram-negative bacteria, whereby only caproic acid- and caprylic acid-LNCs were found to be active against these organisms. The monoglyceride-LNCs were bactericidal, and they killed in a time-dependent manner. Fatty acid-LNCs killed in a concentration-dependent manner. A haemolysis assay was performed to obtain preliminary information on the safety of the tested LNCs. In the case of fatty acid-LNCs, the concentrations at which bacterial growth was inhibited were similar to the haemolytic concentrations. However, monoglyceride-LNCs showed antibacterial action at concentrations much lower than those at which haemolysis was observed. In conclusion, monoglyceride-LNCs are promising candidates as carriers for the encapsulation of antibacterial agents, particularly against S. aureus.

Lipid-Based Liquid Crystals As Carriers for Antimicrobial Peptides: Phase Behavior and Antimicrobial Effect

The number of antibiotic-resistant bacteria is increasing worldwide, and the demand for novel antimicrobials is constantly growing. Antimicrobial peptides (AMPs) could be an important part of future treatment strategies of various bacterial infection diseases. However, AMPs have relatively low stability, because of proteolytic and chemical degradation. As a consequence, carrier systems protecting the AMPs are greatly needed, to achieve efficient treatments. In addition, the carrier system also must administrate the peptide in a controlled manner to match the therapeutic dose window. In this work, lyotropic liquid crystalline (LC) structures consisting of cubic glycerol monooleate/water and hexagonal glycerol monooleate/oleic acid/water have been examined as carriers for AMPs. These LC structures have the capability of solubilizing both hydrophilic and hydrophobic substances, as well as being biocompatible and biodegradable. Both bulk gels and discrete dispersed structures (i.e., cubosomes and hexosomes) have been studied. Three AMPs have been investigated with respect to phase stability of the LC structures and antimicrobial effect: AP114, DPK-060, and LL-37. Characterization of the LC structures was performed using small-angle X-ray scattering (SAXS), dynamic light scattering, ζ-potential, and cryogenic transmission electron microscopy (Cryo-TEM) and peptide loading efficacy by ultra performance liquid chromatography. The antimicrobial effect of the LCNPs was investigated in vitro using minimum inhibitory concentration (MIC) and time-kill assay. The most hydrophobic peptide (AP114) was shown to induce an increase in negative curvature of the cubic LC system. The most polar peptide (DPK-060) induced a decrease in negative curvature while LL-37 did not change the LC phase at all. The hexagonal LC phase was not affected by any of the AMPs. Moreover, cubosomes loaded with peptides AP114 and DPK-060 showed preserved antimicrobial activity, whereas particles loaded with peptide LL-37 displayed a loss in its broad-spectrum bactericidal properties. AMP-loaded hexosomes showed a reduction in antimicrobial activity.

Intermolecular interactions between salmon calcitonin, hyaluronate, and chitosan and their impact on the process of formation and properties of peptide-loaded nanoparticles

The principal aim of this work was to study the formulation of a ternary complex comprising salmon calcitonin (sCT), hyaluronate (HA), and chitosan (CS) in a nanoparticle (NP) format. As interactions between the constituents are possible, their presence and component mass mixing ratio (MMR) and charge mixing ratio (CMR) were investigated to tune the properties of NPs. Intermolecular interactions between sCT and HA as well as sCT and CS were studied by infrared spectroscopy (FTIR) and dynamic viscosity. The impact of MMR, CMR, and HA molecular weight on the sCT loading capacity in NPs and in vitro release properties was determined. sCT complexes to HA via electrostatic interactions and a support for hydrophobic interactions between sCT and HA as well as sCT and CS was found by FTIR. The sCT/HA complex is soluble but, depending on the mass mixing ratio between sCT and HA, NPs and microparticles were also formed indicative of associative phase separation between HA and sCT. The negatively charged HA/CS/sCT NPs were characterized by very high values (above 90%) of peptide association for the systems tested. Also, high sCT loading up to 50% were achieved. The peptide loading capacity and in vitro release properties were dependent on the NP composition. The zeta potential of the NPs without sCT was negative and ranging from -136 to -36 mV, but increased to -84 to -19 mV when the peptide was loaded. The particle size was found to be smaller and ranging 150-230 nm for sCT/NPs in comparison to NPs without sCT (170-260 nm). Short-term storage studies in liquid dispersions showed that the colloidal stability of NPs was acceptable and no release of sCT was observed for up to 3 days. In conclusion, a range of NP systems comprising sCT, HA, and CS was successfully developed and characterized. Such NPs may be considered as a suitable nanoparticulate format for the delivery of sCT.

An intra-articular salmon calcitonin-based nanocomplex reduces experimental inflammatory arthritis

Prolonged inappropriate inflammatory responses contribute to the pathogenesis of rheumatoid arthritis (RA) and to aspects of osteoarthritis (OA). The orphan nuclear receptor, NR4A2, is a key regulator and potential biomarker for inflammation and represents a potentially valuable therapeutic target. Both salmon calcitonin (sCT) and hyaluronic acid (HA) attenuated activated mRNA expression of NR4A1, NR4A2, NR4A3, and matrix metalloproteinases (MMPs) 1, 3 and 13 in three human cell lines: SW1353 chondrocytes, U937 and THP-1 monocytes. Ad-mixtures of sCT and HA further down-regulated expression of NR4A2 compared to either agent alone at specific concentrations, hence the rationale for their formulation in nanocomplexes (NPs) using chitosan. The sCT released from NP stimulated cAMP production in human T47D breast cancer cells expressing sCT receptors. When NP were injected by the intra-articular (I.A.) route to the mouse knee during on-going inflammatory arthritis of the K/BxN serum transfer model, joint inflammation was reduced together with NR4A2 expression, and local bone architecture was preserved. These data highlight remarkable anti-inflammatory effects of sCT and HA at the level of reducing NR4A2 mRNA expression in vitro. Combining them in NP elicits anti-arthritic effects in vivo following I.A. delivery.

Exploring the assembly process and properties of novel crosslinker-free hyaluronate-based polyelectrolyte complex nanocarriers

The aim of this work was to study the formulation of pharmaceutically relevant polyelectrolyte complex nanoparticles (NPs) composed of hyaluronic acid (HA) and chitosan (CS) containing no crosslinkers. The influence of polymer mixing ratio, concentration and molecular weight as well as the type of counterion in chitosan salt on properties of the resulting NPs was examined. Formulations and their components were studied by laser light scattering, viscosity, infrared spectroscopy and microscopy. Physical stability, isoelectric points and cytotoxicity of selected NPs were determined. By appropriate modification of HA molecular weight, stable and non-sedimenting NPs were successfully formed. Sonication was found to be an effective method to reduce the molecular weight of HA from 2882±25 to 176±4 kDa with no chemical changes in the HA structure observed. High molecular weight CS formed micron-sized entities at all compositions investigated. Positively and negatively charged NPs were obtained depending on the mixing ratio of the polymers, with CS glutamate NPs yielding more negatively charged particles compared to CS chloride NPs. The smallest NPs (149±11 nm) were formed using HA with molecular weight of 176 kDa. Cytotoxicity of NPs was dependent on environmental pH but HA was found to exert cytoprotective effects on Caco-2 cells.