Biomedical applications of amino acid-modified chitosans: A review

Advances in Polysaccharides for Cartilage Tissue Engineering Repair: A Review

Cartilage repair has been a significant challenge in orthopedics that has not yet been fully resolved. Due to the absence of blood vessels and the almost cell-free nature of mature cartilage tissue, the limited ability to repair cartilage has resulted in significant socioeconomic pressures. Polysaccharide materials have recently been widely used for cartilage tissue repair due to their excellent cell loading, biocompatibility, and chemical modifiability. They also provide a suitable microenvironment for cartilage repair and regeneration. In this Review, we summarize the techniques used clinically for cartilage repair, focusing on polysaccharides, polysaccharides for cartilage repair, and the differences between these and other materials. In addition, we summarize the techniques of tissue engineering strategies for cartilage repair and provide an outlook on developing next-generation cartilage repair and regeneration materials from polysaccharides. This Review will provide theoretical guidance for developing polysaccharide-based cartilage repair and regeneration materials with clinical applications for cartilage tissue repair and regeneration.

Carrageenan-xanthan nanocomposite film with improved bioadhesion and permeation profile in human skin: A cutaneous-friendly platform for ketoprofen local delivery

Ketoprofen (KET), commonly used for inflammation in clinical settings, leads to systemic adverse effects with prolonged use, mitigated by topical administration. Nanotechnology-based cutaneous forms, like films, may enhance KET efficacy. Therefore, this study aimed to prepare and characterize films containing KET nanoemulsions (F-NK) regarding mechanical properties, chemical composition and interactions, occlusive potential, bioadhesion, drug permeation in human skin, and safety. The films were prepared using a κ-carrageenan and xanthan gum blend (2 % w/w, ratio 3: 1) plasticized with glycerol through the solvent casting method. Non-nanoemulsioned KET films (F-K) were prepared for comparative purposes. F-NK was flexible and hydrophilic, exhibited higher drug content and better uniformity (94.40 ± 3.61 %), maintained the NK droplet size (157 ± 12 nm), and was thinner and lighter than the F-K. This film also showed increased tensile strength and Young's modulus values, enhanced bioadhesion and occlusive potential, and resulted in more of the drug in the human skin layers. Data also suggested that nano-based formulations are homogeneous and more stable than F-KET. Hemolysis and chorioallantoic membrane tests suggested the formulations' safety. Thus, the nano-based film is suitable for cutaneous KET delivery, which may improve the drug's efficacy in managing inflammatory conditions.

Fucoidan/chitosan hydrogels as carrier for sustained delivery of platelet-rich fibrin containing bioactive molecules

Platelet-rich fibrin (PRF), derived from human blood, rich in wound healing components, has drawbacks in direct injections, such as rapid matrix degradation and growth factor release. Marine polysaccharides, mimicking the human extracellular matrix, show promising potential in tissue engineering. In this study, we impregnated the self-assembled fucoidan/chitosan (FU_CS) hydrogels with PRF obtaining PRF/FU_CS hydrogels. Our objective was to analyze the properties of a hydrogel and the sustained release of growth factors from the hydrogel that incorporates PRF. The results of SEM and BET-BJH demonstrated the relatively porous nature of the FU_CS hydrogels. ELISA data showed that combining FU_CS hydrogel with PRF led to a gradual 7-day sustained release of growth factors (VEGF, EGF, IL-8, PDGF-BB, TGF-β1), compared to pure PRF. Histology confirmed ELISA data, demonstrating uniform PRF fibrin network distribution within the FU_CS hydrogel matrix. Furthermore, the FU_CS hydrogels revealed excellent cell viability. The results revealed that the PRF/FU_CS hydrogel has the potential to promote wound healing and tissue regeneration. This would be the first step in the search for improved growth factor release.

Facilitation of Cell Cycle and Cellular Migration of Rat Schwann Cells by O-Carboxymethyl Chitosan to Support Peripheral Nerve Regeneration

O-carboxymethyl chitosan (CM-chitosan), holds high potential as a valuable biomaterial for nerve guidance conduits (NGCs). However, the lack of explicit bioactivity on neurocytes and poor duration that does not match nerve repair limit the restorative effects. Herein, CM-chitosan-based NGC is designed to induce the reconstruction of damaged peripheral nerves without addition of other activation factors. CM-chitosan possesses excellent performance in vitro for nerve tissue engineering, such as increasing the organization of filamentous actin and the expression of phospho-Akt, and facilitating the cell cycle and migration of Schwann cells. Moreover, CM-chitosan exhibits increased longevity upon cross-linking (C-CM-chitosan) with 1, 4-Butanediol diglycidyl ether, and C-CM-chitosan fibers possess appropriate biocompatibility. In order to imitate the structure of peripheral nerves, multichannel bioactive NGCs are prepared from lumen fillers of oriented C-CM-chitosan fibers and outer warp-knitted chitosan pipeline. Implantation of the C-CM-chitosan NGCs to rats with 10-mm defects of peripheral nerves effectively improve nerve function reconstruction by increasing the sciatic functional index, decreasing the latent periods of heat tingling, enhancing the gastrocnemius muscle, and promoting nerve axon recovery, showing regenerative efficacy similar to that of autograft. The results lay a theoretical foundation for improving the potential high-value applications of CM-chitosan-based bioactive materials in nerve tissue engineering.

New N-Methylimidazole-Functionalized Chitosan Derivatives: Hemocompatibility and Antibacterial Properties

Novel imidazole derivatives of the low molecular weight chitosan N-(2-hydroxypropyl)-1H-1,2,3-triazol-4-yl)methyl)-1-methyl-1H-imidazol-3-ium chitosan chloride (NMIC) were synthesized using copper-catalyzed azide-alkyne cycloaddition (CuAAC). The degrees of substitution (DSs) for the new derivatives were 18-76%. All chitosan derivatives (2000 µg/mL) were completely soluble in water. The antimicrobial activity of the new compounds against E. coli and S. epidermidis was studied. The effect of chitosan derivatives on blood and its components was studied. NMIC samples (DS 34-76%) at a concentration <10 μg/mL had no effect on blood and plasma coagulation. Chitosan derivatives (DS 18-76%) at concentrations of ≥83 μg/mL in blood and ≥116.3 μg/mL in plasma resulted in a prolongation of the clotting time of blood and plasma, positively related to the DS. At concentrations up to 9.1 μg/mL, NMIC did not independently provoke platelet aggregation. The degree of erythrocyte hemolysis upon contact with NMIC samples (2.5-2500 μg/mL) was below 4%. The inhibition of blood/plasma coagulation indicates the promising use of the studied samples to modify the surface of medical materials in order to achieve thromboresistance.

Formation of Robust and Adaptive Biopolymers via Non-Covalent Supramolecular Interactions

Biomass-originated materials are the future's next-tier polymers. This work suggests improving mechanical and barrier properties of nature-sourced polymers using non-covalent supramolecular interactions. Polysaccharide chitosan is modified with amino acids via an esterification pathway using a systematic variation of hydrogen bond and aromatic domains (Degrees of substitution 12-49%). These controlled modifications improve stability due to non-covalent interactions, resulting in biopolymers with tailored thermal (decomposition temperature 232-275 °C), mechanical (Young's modulus 540-2667 MPa), and surface properties (roughness 4-40 nm). Chitosan and natural amino acids that are already manufactured at scale are purposely selected. The facile synthesis, controlled properties, stimuli-responsive potential, and inexhaustible origin of the raw materials provide the presented findings with the potential to become the method for the formation of high-performance biodegradable alternatives to petroleum-based polymers that can be used in packaging, food, agriculture, and medicine.

An injectable hydrogel combining medicine and matrix with anti-inflammatory and pro-angiogenic properties for potential treatment of myocardial infarction

One of the main illnesses that put people's health in jeopardy is myocardial infarction (MI). After MI, damaged or dead cells set off an initial inflammatory response that thins the ventricle wall and degrades the extracellular matrix. At the same time, the ischemia and hypoxic conditions resulting from MI lead to significant capillary obstruction and rupture, impairing cardiac function and reducing blood flow to the heart. Therefore, attenuating the initial inflammatory response and promoting angiogenesis are very important for the treatment of MI. Here, to reduce inflammation and promote angiogenesis in infarcted area, we report a new kind of injectable hydrogel composed of puerarin and chitosan via in situ self-assembly with simultaneous delivery of mesoporous silica nanoparticles (CHP@Si) for myocardial repair. On the one hand, puerarin degraded from CHP@Si hydrogel modulated the inflammatory response via inhibiting M1-type polarization of macrophages and expression of pro-inflammatory factors. On the other hand, silica ions and puerarin released from CHP@Si hydrogel showed synergistic activity to improve the cell viability, migration and angiogenic gene expression of HUVECs in both conventional and oxygen/glucose-deprived environments. It suggests that this multifunctional injectable CHP@Si hydrogel with good biocompatibility may be an appropriate candidate as a bioactive material for myocardial repair post-MI.

Multifunctional amphiphilic peptide dendrimer as nonviral gene vectors for effective cancer therapy via combined gene/photodynamic therapies

Gene therapy holds great promise for treatment of gene-associated diseases. However, safe and successful clinical application urgently requires further advancement of constructing efficient delivery systems. Herein, three amphiphilic peptide dendrimers (TTC-L-KRR/KKK/KHH), containing the natural amino acid residues (lysine K, arginine R, and histidine H) and AIE-based photosensitizer (tetraphenylethenethiophene modified cyanoacrylate, TTC) modified with alkyl chain (L), have been designed and prepared for improving therapeutic potency via the combination of gene therapy (GT) and photodynamic therapy (PDT). All three compounds possessed typical aggregation-induced emission (AIE) characteristics and ultralow critical micelle concentrations (CMCs). The liposomes consisting of amphiphilic peptide dendrimers and dioleoylphosphatidylethanolamine (DOPE) can effectively bind DNA into nanoparticles with appropriate sizes, regular morphology and good biocompatibility. Among them, liposomes TTC-L-KKK/DOPE exhibited the highest transfection efficiency up to 5.7-fold as compared with Lipo2000 in HeLa cells. Meanwhile, rapid endocytosis, successful endo/lysosomal escape, gene release and rapid nuclear delivery of DNA revealed the superiority of liposomes TTC-L-KKK/DOPE during gene delivery process. More importantly, efficient reactive oxygen species (ROS) generation by TTC-L-KKK/DOPE led to effective PDT, thus improving therapeutic potency via combining with p53 mediated-gene therapy. Our work brought novel insight and direction for the construction of bio-safe and bio-imaging liposome as the multifunctional nonviral gene vectors for the effective combined gene/photodynamic therapies.

Tissue-engineered bones with adipose-derived stem cells - composite polymer for repair of bone defects

Background: Development of alternative bone tissue graft materials based on tissue engineering technology has gradually become a research focus. Engineered bone composed of biodegradable, biosafe and bioactive materials is attractive, but also challenging. Materials & methods: An adipose-derived stem cell/poly(L-glutamic acid)/chitosan composite scaffold was further developed for construction of biodegradable and bone-promoting tissue-engineered bone. A series of composite scaffold materials with different physical properties such as structure, pore size, porosity and pore diameter was developed. Results: The composite scaffold showed good biodegradability and water absorption, and exhibited an excellent ability to promote bone differentiation. Conclusion: This type of biodegradable scaffold is expected to be applied to the field of bone repair or bone tissue engineering.

Dendrimers as nanoscale vectors: Unlocking the bars of cancer therapy

Chemotherapy is the first choice in the treatment of cancer and is always preferred to other approaches such as radiation and surgery, but it has never met the need of patients for a safe and effective drug. Therefore, new advances in cancer treatment are now needed to reduce the side effects and burdens associated with chemotherapy for cancer patients. Targeted treatment using nanotechnology are now being actively explored as they could effectively deliver therapeutic agents to tumor cells without affecting normal cells. Dendrimers are promising nanocarriers with distinct physiochemical properties that have received considerable attention in cancer therapy studies, which is partly due to the numerous functional groups on their surface. In this review, we discuss the progress of different types of dendrimers as delivery systems in cancer therapy, focusing on the challenges, opportunities, and functionalities of the polymeric molecules. The paper also reviews the various role of dendrimers in their entry into cells via endocytosis, as well as the molecular and inflammatory pathways in cancer. In addition, various dendrimers-based drug delivery (e.g., pH-responsive, enzyme-responsive, redox-responsive, thermo-responsive, etc.) and lipid-, amino acid-, polymer- and nanoparticle-based modifications for gene delivery, as well as co-delivery of drugs and genes in cancer therapy with dendrimers, are presented. Finally, biosafety concerns and issues hindering the transition of dendrimers from research to the clinic are discussed to shed light on their clinical applications.

Some Well-Known Alginate and Chitosan Modifications Used in Adsorption: A Review

Owing to environmental pollution and increasingly strict regulations, heavy metals have attracted the attention of many researchers in various disciplines. Alginate and chitosan derivatives have gained popularity as biosorbents for water treatment. An increase in the number of publications on modified biosorbents for the biosorption of toxic compounds reveals widespread interest in examining the requirements and positive contribution of each modification type. This paper reviews the advantages and disadvantages of using alginate and chitosan for adsorption. Well-known modifications based on chitosan and alginate, namely, grafting, functionalization, copolymerization and cross-linking, as well as applications in the field of adsorption processes, especially amino acid functionalization, are reviewed. The selection criteria for the best biosorbents and their effectiveness and proposed mechanism of adsorption are discussed critically. In the conclusion, the question of why these adsorbents need modification before use is addressed.

Nanotechnologies in Delivery of DNA and mRNA Vaccines to the Nasal and Pulmonary Mucosa

Recent advancements in the field of in vitro transcribed mRNA (IVT-mRNA) vaccination have attracted considerable attention to such vaccination as a cutting-edge technique against infectious diseases including COVID-19 caused by SARS-CoV-2. While numerous pathogens infect the host through the respiratory mucosa, conventional parenterally administered vaccines are unable to induce protective immunity at mucosal surfaces. Mucosal immunization enables the induction of both mucosal and systemic immunity, efficiently removing pathogens from the mucosa before an infection occurs. Although respiratory mucosal vaccination is highly appealing, successful nasal or pulmonary delivery of nucleic acid-based vaccines is challenging because of several physical and biological barriers at the airway mucosal site, such as a variety of protective enzymes and mucociliary clearance, which remove exogenously inhaled substances. Hence, advanced nanotechnologies enabling delivery of DNA and IVT-mRNA to the nasal and pulmonary mucosa are urgently needed. Ideal nanocarriers for nucleic acid vaccines should be able to efficiently load and protect genetic payloads, overcome physical and biological barriers at the airway mucosal site, facilitate transfection in targeted epithelial or antigen-presenting cells, and incorporate adjuvants. In this review, we discuss recent developments in nucleic acid delivery systems that target airway mucosa for vaccination purposes.

Application of Non-Viral Vectors in Drug Delivery and Gene Therapy

Vectors and carriers play an indispensable role in gene therapy and drug delivery. Non-viral vectors are widely developed and applied in clinical practice due to their low immunogenicity, good biocompatibility, easy synthesis and modification, and low cost of production. This review summarized a variety of non-viral vectors and carriers including polymers, liposomes, gold nanoparticles, mesoporous silica nanoparticles and carbon nanotubes from the aspects of physicochemical characteristics, synthesis methods, functional modifications, and research applications. Notably, non-viral vectors can enhance the absorption of cargos, prolong the circulation time, improve therapeutic effects, and provide targeted delivery. Additional studies focused on recent innovation of novel synthesis techniques for vector materials. We also elaborated on the problems and future research directions in the development of non-viral vectors, which provided a theoretical basis for their broad applications.

Editing the Shape Morphing of Monocomponent Natural Polysaccharide Hydrogel Films

Shape-morphing hydrogels can be widely used to develop artificial muscles, reconfigurable biodevices, and soft robotics. However, conventional approaches for developing shape-morphing hydrogels highly rely on composite materials or complex manufacturing techniques, which limit their practical applications. Herein, we develop an unprecedented strategy to edit the shape morphing of monocomponent natural polysaccharide hydrogel films via integrating gradient cross-linking density and geometry effect. Owing to the synergistic effect, the shape morphing of chitosan (CS) hydrogel films with gradient cross-linking density can be facilely edited by changing their geometries (length-to-width ratios or thicknesses). Therefore, helix, short-side rolling, and long-side rolling can be easily customized. Furthermore, various complex artificial 3D deformations such as artificial claw, horn, and flower can also be obtained by combining various flat CS hydrogel films with different geometries into one system, which can further demonstrate various shape transformations as triggered by pH. This work offers a simple strategy to construct a monocomponent hydrogel with geometry-directing programmable deformations, which provides universal insights into the design of shape-morphing polymers and will promote their applications in biodevices and soft robotics.

Development and Evaluation of Curcumin Encapsulated Self-assembled Nanoparticles as Potential Remedial Treatment for PCOS in a Female Rat Model

PURPOSE

Polycystic ovary syndrome (PCOS) is one of the most common endocrinopathies affecting women of reproductive age and leads to metabolic disorders and infertility. The present study was conducted to investigate the therapeutic effects of curcumin (Cur) encapsulated arginine (Arg) and N-acetyl histidine (NAcHis) modified chitosan (Arg-CS-NAcHis/Cur) nanoparticles (NPs).

METHODS

In this study, amphiphilic chitosan (CS) conjugate was developed by modification with hydrophilic arginine (Arg) and hydrophobic N-acetyl histidine (NAcHis) group (Arg-CS-NAcHis). The synthesized conjugate was well characterized by FTIR and NMR studies. Self-assembled nanoparticles based on the synthesized conjugate were developed by simple sonication method and characterized for the physicochemical properties of zeta potential, particle size and drug encapsulation. Next, in vitro drug release, cytotoxicity, and cellular uptake studies of the NPs were evaluated. Finally, the developed nanoparticles were examined for their therapeutic potential against estradiol valerate (EV) induced PCOS rats by evaluating hormone level changes and ovarian morphology.

RESULTS

The results showed that zeta potential of the nanoparticles was 39.8±2.52 mV and the average size was 200 nm. The in vitro drug release profile showed sustained release pattern. Cytotoxicity and cellular uptake studies also showed preferential effectiveness than free curcumin. Both the biochemical and histopathological studies showed positive effects in reverting the symptoms of PCOS rats to normalcy.

CONCLUSION

Curcumin encapsulated arginine and N-acetyl histidine modified chitosan (Arg-CS-NAcHis/Cur) nanoparticles have been successfully developed. The present study suggested that treatment of the nanoparticles might reverse many of the PCOS symptoms. Therefore, these nanoparticles might be used as promising new candidate for delivery of curcumin to treat PCOS.

Preparation and application of chitosan biomaterials in dentistry

Chitosan is a biodegradable and biocompatible natural polysaccharide that has a wide range of applications in the field of dentistry due to its functional versatility and ease of access. Recent studies find that chitosan and its derivatives can be embedded in materials for dental adhesives, barrier membranes, bone replacement, tissue regeneration, and antimicrobial agent to better manage oral diseases. In this paper, we provide a comprehensive overview on the preparation, applications, and major breakthroughs of chitosan biomaterials. Furthermore, incorporation of chitosan additives for the modification and improvement of dental materials has been discussed in depth to promote more advanced chitosan-related research in the future.

L-Lysine Amino Acid Adsorption on Zeolite L: a Combined Synchrotron, X-Ray and Neutron Diffraction Study

Combined neutron and X-ray powder diffraction techniques highlighted the sorption capacity of the acidic L zeolite towards the L-lysine amino acid. The role of zeolite channels in the stabilization of the lysine absorbed and the effect of water on protein structure are elucidated at atomistic level. The stabilization of the L α-helical conformation is related to strong H-bonds between the tail aminogroups of lysine molecules and the Brønsted acid site as well as to complex intermolecular H-bond system between water molecules, zeolite and amino acid. This finding is relevant in the catalytic synthesis of polypeptide, as well as in industrial biotechnology by qualitatively predicting binding behaviour.

A Theoretical Multifractal Model for Assessing Urea Release from Chitosan Based Formulations

This paper reports the calibration of a theoretical multifractal model based on empirical data on the urea release from a series of soil conditioner systems. To do this, a series of formulations was prepared by in situ hydrogelation of chitosan with salicylaldehyde in the presence of different urea amounts. The formulations were morphologically characterized by scanning electron microscopy and polarized light microscopy. The in vitro urea release was investigated in an environmentally simulated medium. The release data were fitted on five different mathematical models, Korsmeyer–Peppas, Zero order, First order, Higuchi and Hixson–Crowell, which allowed the establishment of a mechanism of urea release. Furthermore, a multifractal model, used for the fertilizer release for the first time, was calibrated using these empirical data. The resulting fit was in good agreement with the experimental data, validating the multifractal theoretical model.

Porous chitosan by crosslinking with tricarboxylic acid and tuneable release

Chitosan hydrogels crosslinked with 1,3,5-benzene tricarboxylic acid (BTC) are readily prepared at room temperature by adding aqueous chitosan solution dropwise into BTC-ethanol solution. Highly interconnected porous chitosan materials are subsequently prepared by freeze-drying the chitosan hydrogels. These chitosan materials show porous structures with smaller pores than conventionally prepared chitosan hydrogels via crosslinking with NaOH, genipin or sodium triphosphate. This method of forming chitosan hydrogels with BTC provides the advantage of facile encapsulation of both hydrophobic and hydrophilic compounds, as demonstrated with the model dyes (Oil Red O and Rhodamine B). The release of the hydrophilic dye from the chitosan hydrogels is demonstrated and can be tuned by BTC/chitosan concentrations and the hydrogel drying methods. However, the release of encapsulated hydrophobic dye is negligible.

[Synthesis and cell biological properties of polyaspartic acid drug/gene vector]

OBJECTIVE

Taking polysuccinimide as the main chain, amine side chain and alkyl side chain were grafted to prepare the drug/gene co-delivery vector. The property of the polymers with various side links were investigated to select an optimal vector.

METHODS

Poly-D, L-polysuccinimide was synthesized by polymerization reaction of D, L-aspartic acid as monomer. Therefore, N, N-dimethylenedipropyl-triamine and 3, 3'-diaminodipropylamine were grafted with dodecylamine/adecylamine/octadecylamine at different proportions by ring-opening reaction to obtain amphiphilic PEECs. The structure of the material was confirmed by ¹H NMR; the particle size and surface potential of the micelles were measured by dynamic light scattering; the critical micelle concentration (CMC) was determined by pyrene fluorescent probe; the RNA blocking ability was characterized by agarose gel electrophoresis; the release behavior of the PEECs was examined and the cytotoxicity, cellular uptake and gene silencing efficiency of the PEECs were studied at the cellular level.

RESULTS

A series of PEECs with different grafting rates was successfully synthesized. The particle sizes and surface potential of the PEEC derived micelles were between 250 nm and 350 nm and 27 mV and 45 mV, respectively, with a small CMC value. The RNA binding ratio of PEECs was at a mass ratio of about 0.8:1. MTT assay demonstrated that PEEC micelles had certain cytotoxicity. PEECs had excellent micelle formation, drug-loading and gene binding abilities, particularly, PEEC₁₆-2 showed high gene silencing efficiency at the cellular level.

CONCLUSIONS

PEECs are able to co-delivery drug and gene, and PEEC₁₆-2 micelles have the best ability of drug encapsulation and gene delivery.

Bioinspired Multifunctional Protein Coating for Antifogging, Self-Cleaning, and Antimicrobial Properties

A multifunctional coating with antifogging, self-cleaning, and antimicrobial properties has been prepared based on a mussel-inspired chimeric protein MP-KE, which is the first example that these proteins were successfully applied to fabricate antifogging surfaces. The coating exhibits super hydrophilic properties, as indicated by contact angles less than 5° and high light transmittance similar to bare glass substrates about 90%. The zwitterionic peptides of MP-KE empower water molecules to expand into thin hydrated films rapidly, providing the protein coating with diverse surface functions. Moreover, the coatings have excellent stability and a convenient preparation process because of the mussel adhesive motif of MP-KE which makes the coating anchor onto the surface strongly. As a protein material, this multifunctional coating possesses remarkable biocompatibility and has a potential application prospects in the biomedical and pharmaceutical fields.

Structural and mechanical characteristics of collagen tissue coated with chitosan in a liquid CO2/water system at different pressures

Chitosan coatings of biological heart-valve prostheses enhance their biocompatibility, resistance to pathogenic microflora and lifetime. Collagen tissues can be coated with chitosan in aqueous solution acidified, to make chitosan soluble, with H₂CO₃ formed from a coexisting liquid CO₂ phase under pressure. The advantage of H₂CO₃ is that it can be easily removed after the coating procedure. This study assessed the effects of 6-50 MPa CO₂ pressure during the coating procedure on the structure and mechanical properties of the resulting biocomposite matrices. The dependence of chitosan adsorption on CO₂ pressure was bell-shaped, reaching a maximum adsorption of 0.8 mass % at 40 MPa. Tissue surface became highly porous upon pressure treatment. At 50 MPa, the pores merged to form furrows with lengths of several hundred micrometers, accompanied by collagen fibril reorganisation. Chitosan coating did not affect tissue tensile strength in the axial direction, but increased it by 75% in the radial direction in the tissue coated at 50 MPa pressure. Strain at break, a measure of elasticity, increased in both directions by up to 100% upon coating with chitosan. CO₂ pressure of 30-50 MPa seems thus optimal in terms of chitosan incorporation and tissue mechanical properties.

Regioselective β-Csp3-Arylation of β-Alanine: An Approach for the Exclusive Synthesis of Diverse β-Aryl-β-amino Acids

An approach for the synthesis of a variety of new β-aryl-β-amino acids has been developed via a palladium-catalyzed auxiliary-directed regioselective Csp³-H arylation of the unactivated β-methylene bond of β-alanine. The use of 8-aminoquinoline amide as an auxiliary efficiently directs the desired regioselective β-Csp³-H functionalization. The developed protocol enables the easy and straightforward access to several high-value β-aryl-β-amino acids useful for peptide engineering, starting from inexpensive and readily available β-alanine precursors in moderate to excellent yields.

In vivo nose-to-brain delivery of the hydrophilic antiviral ribavirin by microparticle agglomerates

Nasal administration has been proposed as a potential approach for the delivery of drugs to the central nervous system. Ribavirin (RBV), an antiviral drug potentially useful to treat viral infections both in humans and animals, has been previously demonstrated to attain several brain compartments after nasal administration. Here, a powder formulation in the form of agglomerates comprising micronized RBV and spray-dried microparticles containing excipients with potential absorption enhancing properties, i.e. mannitol, chitosan, and α-cyclodextrin, was developed for nasal insufflation. The agglomerates were characterized for particle size, agglomeration yield, and ex vivo RBV permeation across rabbit nasal mucosa as well as delivery from an animal dry powder insufflator device. Interestingly, permeation enhancers such as chitosan and mannitol showed a lower amount of RBV permeating across the excised nasal tissue, whereas α-cyclodextrin proved to outperform the other formulations and to match the highly soluble micronized RBV powder taken as a reference. In vivo nasal administration to rats of the agglomerates containing α-cyclodextrin showed an overall higher accumulation of RBV in all the brain compartments analyzed as compared with the micronized RBV administered as such without excipient microparticles. Hence, powder agglomerates are a valuable approach to obtain a nasal formulation potentially attaining nose-to-brain delivery of drugs with minimal processing of the APIs and improvement of the technological and biopharmaceutical properties of micronized API and excipients, as they combine optimal flow properties for handling and dosing, suitable particle size for nasal deposition, high surface area for drug dissolution, and penetration enhancing properties from excipients such as cyclodextrins.

Balancing antimicrobial activity with biological safety: bifunctional chitosan derivative for the repair of wounds with Gram-positive bacterial infections

Because of the balance between antimicrobial activity and biological safety, the bifunctional chitosan derivative could control infections and promote healing simultaneously.

Drug nanocarrier agents based on starch-g-amino acids

Introduction: In the recent decades, starch has been modified using different methods for the various forms of applications. Some new starch derivatives were prepared through a simple and convenient method in the grafting of amino acids: L-alanine, L-leucine and L-phenyl alanine to starch. Methods: First, the amine groups of amino acids were protected using phthalic anhydride then the acidic side of amino acids were activated with chlorination using thionyl chloride, and the resultant acid chlorides were reacted with starch in aqueous media at room temperature. Results: Performing the various spectroscopy experiments on the obtained compounds showed that the new derivative of starch has been formed. The structure of all synthesized materials was determined and confirmed using common spectroscopy methods and their thermal behavior was examined using DSC experiment. Conclusion: New amino acid derivatives of starch and their nanocarriers successfully prepared through a simple and convenient method. The size of nanocarriers evaluated using DLS and TEM experiments. The spherical shape of particles shows that nanocarriers have been formed and the size of these particles are approximately 92, 137 and 97 nm. Performing the wettability test determined that all the resulted materials are soluble in water. Nanocarriers of the obtained modified starches were prepared using dialysis method and naproxen was utilized as a model drug molecule. The drug release dynamics in buffered solution were studied and investigation of the drug release mechanism showed that in case of L-alanine- and L-phenylalanine-modified starches, drug release followed the Fickian diffusion with a slight deviation.

Development of genipin-crosslinked fucoidan/chitosan-N-arginine nanogels for preventing Helicobacter infection

AIM

This study aims to validate the anti-Helicobacter pylori efficacy of amoxicillin-loaded nanoparticles and nanogels with pH-responsive and site-specific drug release properties against H. pylori infection.

MATERIALS & METHODS

Genipin-crosslinked low molecular weight fucoidan/chitosan-N-arginine nanogels (FCSA) were prepared for targeted delivery of amoxicillin to the site of H. pylori infected AGS gastric epithelial cells.

RESULTS

The negatively charged nanogels (n-FCSA) adhered to H. pylori and exhibited pH-responsive drug release property to reduce cytotoxic effects in H. pylori infected AGS cells.

CONCLUSION

These in vitro findings suggest that n-FCSA nanogels are potential carriers for H. pylori specific delivery of antibacterial agents, and provide the basis for further studies on the clinical use of the nanogels.

pH Triggered Size Increasing Gene Carrier for Efficient Tumor Accumulation and Excellent Antitumor Effect

High efficiency and serum resistant capacity are important for gene carrier in vivo usage. In this study, transfection efficiency and cell toxicity of polyethylenimine (PEI) (branched, Mw = 25K) was remarkably improved, when mixed with polyanion (polyethylene glycol-polyglutamic acid (PEG-PLG) or polyglutamic acid (PLG)). Different composite orders of PEI, polyanion, and gene, for example, PEI is first complexed with DNA, and then with polyanion, or PEI is first complexed with polyanion, and then with DNA, were studied. Results showed that only the polyanion/PEI complexes exhibited additional properties, such as decreased pH, resulting in increased particle size, as well as enhanced serum resistance capability and improved tumor accumulation. The prepared gene carrier showed excellent antitumor effect, with no damage on major organs, which is suitable for in vivo gene antitumor therapy.

Non-viral strategies for ocular gene delivery

The success of gene therapy relies on efficient gene transfer and stable transgene expression. The in vivo efficiency is determined by the delivery vector, route of administration, therapeutic gene, and target cells. While some requirements are common to several strategies, others depend on the target disease and transgene product. Consequently, it is unlikely that a single system is suitable for all applications. This review examines current gene therapy strategies, focusing on non-viral approaches and the use of natural polymers with the eye, and particularly the retina, as their gene delivery target.