The effect of freeze-drying on mucoadhesion and transport of acrylated chitosan nanoparticles

Comparative analysis of classic network vs. nanogel junction network in konjac glucomannan/kappa carrageenan hybrid hydrogels

The three-dimensional network architecture of hydrogels significantly influences their mechanical and physical properties; therefore, understanding them is essential for designing optimized hydrogel-based biomaterials. This study presents a comparative analysis of two hybrid hydrogels composed of konjac glucomannan (KGM) and kappa carrageenan (KCAR) with the same stiffness (5.2-5.7 kPa and 1.6-1.7 kPa) thus similar cross-linking density but different network architectures: a classic network formed by extended polysaccharide interactions and a nanogel junction network where nanoscale cross-linked KCAR (KCAR-NGs) links KGM chains. The mechanical behavior, dissolution, and diffusion characteristics were examined, revealing that the classic network demonstrates superior tensile resistance, elongation, and solvent-induced swelling resistance, leading to slower dissolution rates and higher viscosity. Conversely, the nanogel junction network offers higher permeability for small molecules and faster dissolution, suggesting a more open network structure. These findings highlight the nanogel-based hydrogels' advantages for biomedical applications requiring stability, permeability, and rapid dissolution without high temperatures or chelating agents. This study underscores the potential of nanogel junction networks to balance hydrogel stiffness and permeability, advancing the design of hydrogel-based biomaterials.

Exploring Mucoadhesive and Toxicological Characteristics Following Modification of Linear Polyethylenimine with Various Anhydrides

Linear polyethylenimine (L-PEI) has numerous applications, such as in pharmaceutical formulations, gene delivery, and water treatment. However, due to the presence of secondary amine groups, L-PEI shows a relatively high toxicity and low biocompatibility. Here, various organic anhydrides were used to modify L-PEI to reduce its toxicity and enhance its functionality. We selected methacrylic anhydride, crotonic anhydride, maleic anhydride, and succinic anhydride to modify L-PEI. The structure of the resulting derivatives was characterized using 1H NMR and FTIR spectroscopies, and their behavior in aqueous solutions was studied using turbidimetric and electrophoretic mobility measurements over a broad range of pHs. A fluorescence flow through method determined the mucoadhesive properties of the polymers to the bovine palpebral conjunctiva. Methacrylated L-PEI and crotonylated L-PEI showed strong mucoadhesive properties at pH 7.4, likely due to covalent bonding with mucin thiol groups. In contrast, maleylated and succinylated L-PEI were poorly mucoadhesive as the pH was above their isoelectric point, resulting in electrostatic repulsion between the polymers and mucin. The toxicity of these polymers was evaluated using in vivo assays with planaria and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) cell viability assay in human alveolar epithelial cells. Moreover, the irritancy of polymers was assessed using a slug mucosa irritation assay. The results demonstrated that anhydride modification mitigated the adverse toxicity effects seen for parent L-PEI.

Chrysin loaded bilosomes improve the hepatoprotective effects of chrysin against CCl4 induced hepatotoxicity in mice

In the present work, chrysin loaded bilosomes were formulated, characterized and evaluated to enhance the hepatoprotective activity of drug. Accordingly, chrysin loaded bilosomes were prepared by applying the thin film hydration method; also, fractional factorial design was used to optimize the production conditions of nanoformulations. The prepared formulations were subjected to different methods of characterization; then the hepatoprotective activity of the optimized one was evaluated in the CCl4 hepatointoxicated mice model. Optimized chrysin loaded bilosomes showed a spherical shape with a particle size of 232.97 ± 23 nm, the polydispersity index of 0.35 ± 0.01, the zeta potential of -44.5 ± 1.27 mv, the entrapment efficiency of 96.77 ± 0.18%, the drug loading % of 6.46 ± 0.01 and the release efficiency of 42.25 ± 1.04 during 48 h. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging assay demonstrated the superiority of the anti-oxidant potential of chrysin loaded bilosomes, as compared to pure chrysin. This was in agreement with histopathological investigations, showing significant improvement in serum hepatic biomarkers of CCl4 intoxicated mice treated with chrysin loaded bilosomes, as compared with free chrysin. These results, thus, showed the potential use of bilosomes to enhance the hepatoprotective activity of chrysin via oral administration.

Lyophilization for Formulation Optimization of Drug-Loaded Thermoresponsive Polyelectrolyte Complex Nanogels from Functionalized Hyaluronic Acid

The lyophilization of nanogels is practical not only for their long-term conservation but also for adjusting their concentration and dispersant type during reconstitution for different applications. However, lyophilization strategies must be adapted to each kind of nanoformulation in order to minimize aggregation after reconstitution. In this work, the effects of formulation aspects (i.e., charge ratio, polymer concentration, thermoresponsive grafts, polycation type, cryoprotectant type, and concentration) on particle integrity after lyophilization and reconstitution for different types of polyelectrolyte complex nanogels (PEC-NGs) from hyaluronic acid (HA) were investigated. The main objective was to find the best approach for freeze-drying thermoresponsive PEC-NGs from Jeffamine-M-2005-functionalized HA, which has recently been developed as a potential platform for drug delivery. It was found that freeze-drying PEC-NG suspensions prepared at a relatively low polymer concentration of 0.2 g.L−1 with 0.2% (m/v) trehalose as a cryoprotectant allow the homogeneous redispersion of PEC-NGs when concentrated at 1 g.L−1 upon reconstitution in PBS without important aggregation (i.e., average particle size remaining under 350 nm), which could be applied to concentrate curcumin (CUR)-loaded PEC-NGs for optimizing CUR content. The thermoresponsive release of CUR from such concentrated PEC-NGs was also reverified, which showed a minor effect of freeze-drying on the drug release profile.

Recent Advances in Freeze-Drying: Variables, Cycle Optimization, and Innovative Techniques

Freeze-drying (FD) is the most substantial drying technique utilized in the pharmaceutical and biopharmaceutical industries. It is a drying process where the solvent is crystallized at low temperatures and then sublimed from the solid-state directly into the vapor phase. Although FD possesses several merits as its suitability for thermolabile materials and its ability to produce dry products with high-quality attributes, it is a complex and prolonged process that requires optimization of both; process and formulation variables. This review attains to disassemble freeze-drying complications through a detailed explanation of the lyophilization concept, stages, the factors influencing the process including controlled ice nucleation, and the modified and innovative freeze-drying technologies proposed in recent years to overcome the shortage of traditional freeze-drying. In addition, this work points out the quality by design (QbD), critical quality of attributes (CQAs), limitations, and drawbacks of lyophilization.HighlightsLyophilization is a propitious drying technique for thermolabile materials.Optimizing the lyophilization cycle requires controlling the process parameters.The formulation excipients and the dispersion medium play crucial roles in designing a successful process.Numerous approaches were developed to ameliorate the lyophilization performance.

Recent advances in functionally modified polymers for mucoadhesive drug delivery

Novel methods for the delivery of drugs other than the conventional method of oral administration have been a thrust area of research for a few decades. Mucoadhesive delivery of drugs opened up a new domain where rapid and patient-friendly delivery of drugs can be achieved. Delivery of drugs through the mucosal sites such as buccal, nasal, ocular, sublingual, rectal and vaginal facilitates bypassing the first-pass metabolism and the drug reaches the systemic circulation directly. This helps to increase the bioavailability of the drug. The study of the chemical characteristics of polymers with mucoadhesive properties and how the molecules or the pharmaceuticals are transported across the mucosa is very much needed for the advancement of research in this field. And at the same time, it is very pertinent to know about the anatomy and the physiology of the mucosal tissue and its variation in different regions of the body. In this review, we try to present a comprehensive understanding of relevant topics of mucoadhesion giving more emphasis on the mechanism of transport of drugs across mucosa, and different possible functional modifications of polymers to enhance the property of mucoadhesion.

Nanostructured polyelectrolyte complexes based on chitosan and sodium alginate containing rifampicin for the potential treatment of tuberculosis

Nanostructured polyelectrolyte complexes (nano PECs) were obtained by polyelectrolyte complexation technique from chitosan (CS) and sodium alginate (SA). Different polymer proportions were tested, as well as the addition order and homogenization type, to assess the influence on the nano PECs characteristics. The spherical shape and nanometric scale of the systems were observed by scanning electron microscopy (SEM). Nano PECs size, PDI and zeta potential ranged from 252 to 616 nm, from 0.22 to 0.73 and -50 to 30 mV, respectively. The increase of polymer proportion and the ultra-turrax homogenization led to the enlargement of particles size and PDI. However, no influence was observed on the zeta potential. The NP1s-Rb and NP4s-Rb, obtained through the sonicator with rifampicin (RIF) added before the CS and SA complexation, were selected due to the most promising characteristics of diameter (301 and 402 nm), PDI (0.27 and 0.26) and RIF incorporation (78 and 69%,). The release profiles of RIF incorporated in both nano PECs were similar, with a sustained release of the drug for 180 minutes in phosphate buffer pH (7.2). The Weibull and the Korsmeyer-Peppas models better describe the RIF release from NP1s-Rb and NP4s-Rb, respectively, demonstrating that the release process was driven by different mechanism according the particle composition. The nano PECs were lyophilized to prolong it stability and for possible nebulization. The addition of dextrose to the system allowed for resuspension after lyophilization. Therefore, with the results obtained, the incorporation of RIF in nano PECs based on CS and SA presents a promising system for the treatment of tuberculosis.

Influence of the Dispersion Medium and Cryoprotectants on the Physico-Chemical Features of Gliadin- and Zein-Based Nanoparticles

The evaluation of the physico-chemical features of nanocarriers is fundamental because the modulation of these parameters can influence their biological and in vivo fate. This work investigated the feasibility of saline, 5% w/v glucose and phosphate-buffered saline solution, as polar media for the development of nanoparticles made up of two vegetal proteins, zein from corn and gliadin from wheat, respectively. The physico-chemical features of the various systems were evaluated using dynamic and multiple light scattering techniques, and the results demonstrate that the 5% w/v glucose solution is a feasible medium to be used for their development. Moreover, the best formulations were characterized by the aforementioned techniques following the freeze-drying procedure. The aggregation of the zein nanoparticles prepared in water or glucose solution was prevented by using various cryoprotectants. Mannose confirmed its crucial role in the cryopreservation of the gliadin nanosystems prepared in both water and glucose solution. Sucrose and glucose emerged as additional useful excipients when they were added to gliadin nanoparticles prepared in a 5% glucose solution. Specifically, their protective effect was in the following order: mannose > sucrose > glucose. The results obtained when using specific aqueous media and cryoprotectants permitted us to develop stable zein or gliadin nanoparticles as suspension or freeze-dried formulations.

Functionalized Particles Designed for Targeted Delivery

Pure bioactive compounds alone can only be exceptionally administered in medical treatment. Usually, drugs are produced as various forms of active compounds and auxiliary substances, combinations assuring the desired healing functions. One of the important drug forms is represented by a combination of active substances and particle-shaped polymer in the nano- or micrometer size range. The review describes recent progress in this field balanced with basic information. After a brief introduction, the paper presents a concise overview of polymers used as components of nano- and microparticle drug carriers. Thereafter, progress in direct synthesis of polymer particles with functional groups is discussed. A section is devoted to formation of particles by self-assembly of homo- and copolymer-bearing functional groups. Special attention is focused on modification of the primary functional groups introduced during particle preparation, including introduction of ligands promoting anchorage of particles onto the chosen living cell types by interactions with specific receptors present in cell membranes. Particular attention is focused on progress in methods suitable for preparation of particles loaded with bioactive substances. The review ends with a brief discussion of the still not answered questions and unsolved problems.

Freeze-drying of nanoparticles: How to overcome colloidal instability by formulation and process optimization

Lyophilization of nanoparticle (NP) suspensions is a promising technology to improve stability, especially during long-term storage, and offers new routes of administration in solid state. Although considered as a gentle drying process, freeze-drying is also known to cause several stresses leading to physical instability, e.g. aggregation, fusion, or content leakage. NPs are heterogeneous regarding their physico-chemical properties which renders them different in their sensitivity to lyophilization stress and upon storage. But still basic concepts can be deducted. We summarize basic colloidal stabilization mechanisms of NPs in the liquid and the dried state. Furthermore, we give information about stresses occurring during the freezing and the drying step of lyophilization. Subsequently, we review the most commonly investigated NP types including lipophilic, polymeric, or vesicular NPs regarding their particle properties, stabilization mechanisms in the liquid state, and important freeze-drying process, formulation and storage strategies. Finally, practical advice is provided to facilitate purposeful formulation and process development to achieve NP lyophilizates with high colloidal stability.

Evaluation of the bioaccessibility of tetrahydrocurcumin-hyaluronic acid conjugate using in vitro and ex vivo models

Tetrahydrocurcumin-hyaluronic acid (THC-HA) conjugate was synthesized in order to improve the bioaccessibility of tetrahydrocurcumin (THC). The successful conjugation was confirmed by the results from ¹H-nuclear magnetic resonance (¹H NMR), Differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Bioaccessibility enhancement from the THC-HA conjugate compared to the free crystalline THC suspension was demonstrated by the results from ex vivo Franz diffusion cell using small intestine from porcine and in vitro TNO dynamic gastrointestinal model-1 (TIM-1). Additionally, in vitro release was studied, and the integrity of the conjugate in both simulated gastric and intestinal conditions was found to maintain for up to 4 h. Mucoadhesive assay and rheological results indicated that the mucoadhesive property of THC-HA, in combination with the aqueous solubility enhancement, might contribute to the increased bioaccessibility. This study provides a promising approach to enhance the bioaccessibility of tetrahydrocurcumin through the innovative conjugation with hyaluronic acid.

Development of a chitosan-modified PLGA nanoparticle vaccine for protection against Escherichia coli K1 caused meningitis in mice

Background

Escherichia coli K1 (E. coli K1) caused neonatal meningitis remains a problem, which rises the urgent need for an effective vaccine. Previously, we rationally designed and produced the recombinant protein OmpAVac (Vo), which elicited protective immunity against E. coli K1 infection. However, Vo has limited stability, which hinders its future industrial application.

Method

Chitosan-modified poly (lactic-co-glycolic acid) (PLGA) nanoparticles were prepared and used as carried for the recombinant Vo. And the safety, stability and immunogenicity of Vo delivered by chitosan-modified PLGA nanoparticles were tested in vitro and in a mouse model of bacteremia.

Results

We successfully generated chitosan-modified PLGA nanoparticles for the delivery of recombinant Vo (VoNP). In addition, we found that a freeze-drying procedure increases the stability of the VoNPs without changing the shape, size distribution and encapsulation of the Vo protein. Unlike aluminum adjuvant, the nanoparticles that delivered Vo were immunoprotective in mice even after storage for as long as 180 days.

Conclusions

We identified an effective strategy to improve the stability of Vo to maintain its immunogenicity, which will contribute to the future development of vaccines against E. coli K1.

Molecular and cellular cues governing nanomaterial-mucosae interactions: from nanomedicine to nanotoxicology

Mucosal tissues constitute the largest interface between the body and the surrounding environment and they regulate the access of molecules, supramolecular structures, particulate matter, and pathogens into it. All mucosae are characterized by an outer mucus layer that protects the underlying cells from physicochemical, biological and mechanical insults, a mono-layered or stratified epithelium that forms tight junctions and controls the selective transport of solutes across it and associated lymphoid tissues that play a sentinel role. Mucus is a gel-like material comprised mainly of the glycoprotein mucin and water and it displays both hydrophilic and hydrophobic domains, a net negative charge, and high porosity and pore interconnectivity, providing an efficient barrier for the absorption of therapeutic agents. To prolong the residence time, absorption and bioavailability of a broad spectrum of active compounds upon mucosal administration, mucus-penetrating and mucoadhesive particles have been designed by tuning the chemical composition, the size, the density, and the surface properties. The benefits of utilizing nanomaterials that interact intimately with mucosae by different mechanisms in the nanomedicine field have been extensively reported. To ensure the safety of these nanosystems, their compatibility is evaluated in vitro and in vivo in preclinical and clinical trials. Conversely, there is a growing concern about the toxicity of nanomaterials dispersed in air and water effluents that unintentionally come into contact with the airways and the gastrointestinal tract. Thus, deep understanding of the key nanomaterial properties that govern the interplay with mucus and tissues is crucial for the rational design of more efficient drug delivery nanosystems (nanomedicine) and to anticipate the fate and side-effects of nanoparticulate matter upon acute or chronic exposure (nanotoxicology). This review initially overviews the complex structural features of mucosal tissues, including the structure of mucus, the epithelial barrier, the mucosal-associated lymphatic tissues and microbiota. Then, the most relevant investigations attempting to identify and validate the key particle features that govern nanomaterial-mucosa interactions and that are relevant in both nanomedicine and nanotoxicology are discussed in a holistic manner. Finally, the most popular experimental techniques and the incipient use of mathematical and computational models to characterize these interactions are described.

Production and Characterization of Anti-CCR5 siRNA-Loaded Polycaprolactone Nanoparticles for Topical Pre-exposure Prophylaxis

Topical posttranscriptional silencing of host factors involved in HIV-1 sexual transmission, such as CCR5, presents the potential to prevent new cases of infection. However, issues concerning proper engineering of safe and effective delivery systems for anti-CCR5 siRNA may impair the ability to yield suitable silencing at the mucosal level. Here we describe the production protocol of anti-CCR5 siRNA-loaded polycaprolactone-based nanoparticles (≈100 nm). Furthermore, we present data regarding the physicochemical and in vitro biological characterization of obtained nanosystems, which support their potential as microbicide candidates for topical pre-exposure prophylaxis of HIV-1 infection.

The Vaginal-PVPA: A Vaginal Mucosa-Mimicking In Vitro Permeation Tool for Evaluation of Mucoadhesive Formulations

Drug administration to the vaginal site has gained increasing attention in past decades, highlighting the need for reliable in vitro methods to assess the performance of novel formulations. To optimize formulations destined for the vaginal site, it is important to evaluate the drug retention within the vagina as well as its permeation across the mucosa, particularly in the presence of vaginal fluids. Herewith, the vaginal-PVPA (Phospholipid Vesicle-based Permeation Assay) in vitro permeability model was validated as a tool to evaluate the permeation of the anti-inflammatory drug ibuprofen from liposomal formulations (i.e., plain and chitosan-coated liposomes). Drug permeation was assessed in the presence and absence of mucus and simulated vaginal fluid (SVF) at pH conditions mimicking both the healthy vaginal premenopausal conditions and vaginal infection/pre-puberty/post-menopause state. The permeation of ibuprofen proved to depend on the type of formulation (i.e., chitosan-coated liposomes exhibited lower drug permeation), the mucoadhesive formulation properties and pH condition. This study highlights both the importance of mucus and SVF in the vaginal model to better understand and predict the in vivo performance of formulations destined for vaginal administration, and the suitability of the vaginal-PVPA model for such investigations.