Designing Formulation Strategies for Enhanced Stability of Therapeutic Peptides in Aqueous Solutions: A Review

Comprehensive analyses of meat quality and metabolome alterations with aging under different aging methods in beef

The impacts of various aging techniques on meat quality and metabolism alterations over time were investigated. Meat tenderness improved with aging, whereas prolonged aging negatively impacted color and oxidative stability. Dry-aging (DA) group exhibited significantly higher (P < 0.05) weight loss, lipid oxidation, and carbonyl contents, along with significantly lower (P < 0.05) centrifugal loss, cooking loss, a* value, and sulfhydryl content compared to wet-aging (WA) group. Substantial amounts of small peptides, amino acids, and amino acid derivatives were detected in the 28 d aged samples. Higher abundances of benzenoids, lipids and lipid-like molecules, amino acids and their derivatives, and alkyl phosphates were found in the WA group, while dialkyl ethers, fatty acids, fatty acid metabolites, and hydroxy acids showed higher intensities in the DA and dry-aging in bag groups. These findings provide comprehensive metabolome information and their underlying relation with meat quality changes during aging under different aging methods.

Engineering the Bioactive Profile of Medicinal Peptides by Multiarm Polyethylene Glycol Conjugation

PEGylation plays a crucial role in peptide modification and has been widely applied in the field of biomedicine, demonstrating significant potential for enhancing peptide drug performance. Herein, we synthesized melittin peptides modified with single arm, double arm, and four arm of PEG12, utilizing lysine side chains as branching points, to systematically investigate the effects of multiarm PEGylation on toxicity, hemolytic activity, stability, and membrane-disrupting ability. Our results revealed that increasing the number of PEG arms significantly reduced the cytotoxicity and hemolytic activity of melittin (with IC50 increasing approximately 20-fold) while simultaneously enhancing serum stability. These effects were attributed to the improved water solubility and altered hydrophilicity/hydrophobicity balance at the N-terminus, which modulated the interactions with cell membranes and reduced the membrane penetration capacity. Meanwhile, the steric hindrance effect that was caused by multiarm PEG modification prevented the destruction of cell membranes by melittin. The strategy of terminal PEGylation was expected to minimize systemic toxicity and in vivo degradation. Collectively, our findings highlight the critical role of the topological structure PEG in fine-tuning peptide drug performance, providing valuable insights for the design of safer and more effective peptide-based therapeutics.

Understanding peptide hormones: from precursor proteins to bioactive molecules

Peptide hormones are fundamental regulators of biological processes involved in homeostasis regulation and are often dysregulated in endocrine diseases. Despite their biological significance and established therapeutic potential, there is still a gap in our knowledge of their processing and post-translational modifications, as well as in the technologies for their discovery and detection. In this review, we cover insights into the peptidome landscape, including the proteolytic processing and post-translational modifications of peptide hormones. Understanding the full landscape of peptide hormones and their modifications could provide insights into leveraging proteolytic mechanisms to identify novel peptides with therapeutic potential. Therefore, we also discuss the need for future research aiming at better predicting, detecting, and characterizing new peptides with biological activities.

Effect of osmolytes on the conformational stability of Aβ(25-35): A circular dichroism analysis

Alzheimer's (AD) is a neurodegenerative disease characterized by the onset and progression of mental decline. AD aetiopathogenesis is still questioned; however, according to one of the most accredited hypotheses, the accumulation of amyloid plaques formed by aggregated Aβ peptides is the primary cause of neuronal function loss. Accordingly, hundreds of molecules have been screened for their possible action to prevent or destroy amyloid aggregates. Following this track, osmolytes, naturally occurring small molecules produced by several organisms in response to external stressors, were recently evaluated as modulators of Aβ aggregation. In this study, we examined the conformational stability of Aβ(25-35) when exposed to the osmolytes acetylcholine (ACh), succinylcholine (SCh), and betaine (Bet). Aβ(25-35) is the shortest fragment known for replicating the aggregation process seen in Aβ peptides. By collecting circular dichroism (CD) spectra in water and different membrane-mimicking systems, we investigated the potential of the mentioned osmolytes to stabilize the soluble conformations of Aβ(25-35) and preserve them from denaturing conditions. Our data suggest that Bet is a promising small molecule that can safeguard the soluble form of Aβ peptide and is effective in counteracting environmental conditions by favoring the amyloid aggregation associated with pathology progression.

Dental plaque-inspired peptide engineered to control plaque accumulation

Effective control of plaque accumulation is an important strategy for reducing the risk of both localized oral health issues and systemic diseases associated with plaque. However, existing approaches for preventing plaque accumulation exhibit some limitations, such as insufficient compatibility with the oral microbiota and tissues, as well as inconvenience in their use. Herein, inspired by dental plaque, a new class of peptides featuring excellent anti-fouling performance is successfully developed. Our peptides consist of a salivary-acquired peptide with tooth surface-selective adhesion, a zwitterionic peptide with anti-adhesion property, and four proline residues that provide structural rigidity. We conduct a series of progressive experiments, including molecular dynamics simulation and assessments of the anti-fouling performance of our peptides on hydroxyapatite slices, human tooth enamel slices, and ex vivo human teeth. The results demonstrate that our peptides possess the abilities of rapid anchoring on tooth surfaces and effective inhibiting protein and bacterial adhesion. These characteristics enable our peptide to efficiently control plaque accumulation through rinsing or spraying while preserving the balance of the oral microbiota. These findings open an appealing avenue for the development of anti-fouling agents for controlling plaque accumulation on tooth surfaces.

Advancing Nanotechnology: Targeting Biofilm-Forming Bacteria with Antimicrobial Peptides

Nanotechnology offers innovative solutions for addressing the challenges posed by biofilm-forming bacteria, which are highly resistant to conventional antimicrobial therapies. This review explores the integration of pharmaceutical nanotechnology with antimicrobial peptides (AMPs) to enhance the treatment of biofilm-related infections. The use of various nanoparticle systems-including inorganic/metallic, polymeric, lipid-based, and dendrimer nanostructures-provides promising avenues for improving drug delivery, targeting, and biofilm disruption. These nanocarriers facilitate the penetration of biofilms, down-regulate biofilm-associated genes, such as ALS1, ALS3, EFG1, and HWP1, and inhibit bacterial defense mechanisms through membrane disruption, reactive oxygen species generation, and intracellular targeting. Furthermore, nanoparticle formulations such as NZ2114-NPs demonstrate enhanced efficacy by reducing biofilm bacterial counts by several orders of magnitude. This review highlights the potential of combining nanotechnology with AMPs to create novel, targeted therapeutic approaches for combatting biofilm-related infections and overcoming the limitations of traditional antimicrobial treatments.

Synthesis of a retro-GFOGER Adamantane-Based Collagen Mimetic Peptide Imbibed in a Hyaluronic Acid Hydrogel for Enhanced Wound Healing

This study reported the synthesis and formulation of an adamantane-based collagen mimetic peptide (CMP) hydrogel containing the integrin-binding motif retro-GFOGER, designed to enable the controlled delivery of CMPs with the ability of direct wound healing for the potential treatment of acute wounds. Initially, two adamantane-functionalized CMPs (peptides NL008 and NL010) were synthesized, characterized, and comparatively screened for their in vitro biocompatibility and bioactivity. In vitro evaluations of scratch closure and biocompatibility were assessed on human-derived keratinocytes. Release and permeation of the peptides were evaluated in vitro and ex vivo. Wound closure rates and histological evaluations were performed on male Sprague-Dawley rats over 3, 7, and 14 days for the NL010-HAgel formulation. Peptide NL010 was found to be the most suitable candidate among the adamantane CMPs. For a comparative study, peptide NL010 and its palmitic acid analogue, NL009, were loaded into a hyaluronic acid (HA) hydrogel and lyophilized. The CMP hydrogels exhibited porosity (<30 μm) and were viscoelastic solids. The physicomechanical properties of the formulations showed optimal characteristics for application as wound dressings in terms of textural profile. Peptide NL008 exhibited lower bioactivity and cell viability compared to NL009 and NL010 across various concentrations and cell lines. Peptide release from NL009-HAgel and NL010-HA gel was 74% and 83%, respectively. Across an ex vivo porcine skin membrane, the CMP-HAgel showed good permeation and was retained in the epidermis and superficial dermis. CMP-HAgel at 0.1% (w/v) showed better HaCaT cell viabilities. In vitro assays demonstrated that the NL010-HA gel achieved scratch closure (99.9%) within 24 h, while the NL009-HAgel showed scratch closure (93.7%) within the same time frame. In vivo, NL010-HAgel improved healing by enhancing epithelialization and granulation tissue deposition (via fibroblast and collagen responses). The findings of this study suggested that the CMP cell-instructive hydrogel is a promising platform with the potential to accelerate wound healing.

New approaches for screening grape seed peptides as colourimetric modulators by malvidin-3-O-glucoside stabilisation

The colour of red wine is due to the presence of anthocyanins and their derived pigments, with malvidin-3-O-glucoside being the most predominant. Due to their chemical conformation, anthocyanins are susceptible to several conditions and have limited stability. Through copigmentation processes, anthocyanins can interact non-covalently with other molecules to enhance their stability. As a natural source of proteins and peptides, grape seeds are of particular interest because they may be of significant techno-functional value in the modulation of wine quality characteristics, such as acting as copigments to enhance colour stability. The proposed methodology allowed predicting in-depth insights into the molecular-level nature of interaction between the identified peptides when complexed with malvidin 3-O-glucoside and their colour stabilising properties. Thereby, allowing a prior screening in silico to facilitate their future application in experimental assays, such as obtaining the tested peptides with the characteristics already studied by means of grape seed meal directed hydrolysis.

Cleaving the way for heterologous peptide production: An overview of cleavage strategies

One of the main bottlenecks for recombinant peptide production is choosing the proper cleavage method to remove fusion protein tags from target peptides. While these tags are crucial for inhibiting the activity of the target peptide during heterologous expression, incorporating a cleavage site is essential for their later removal, ensuring the pure sequencing of the peptide. This review evaluates different cleavage methods, including protease-mediated, self-cleavable protein, and chemical-mediated sites, regarding their advantages and limitations. For instance, intein, Npro EDDIE, enterokinase, factor Xa, SUMO, and CNBr are options for residue-free cleavage. Although protease-mediated cleavage is widely used, it can be expensive, due to its own cost added to the whole process. As an alternative, self-cleavable sites eliminate the requirement for proteinases. Another crucial step in defining the proper cleavage method is cost consideration, which relates to the purpose of peptide production. Here, we explore a range of cleavage approaches, meeting the needs of both cost-constrained applications and a more flexible budget. Overall, selecting the most suitable cleavage method should be based on careful consideration of toxicity, cost, accuracy, and specific application requirements to ensure a state-of-the-art approach.

Role of Copper and Zinc Ions in the Hydrolytic Degradation of Neurodegeneration-Related Peptides

Spontaneous cleavage reactions normally occur in vivo on amino acid peptide backbones, leading to fragmentation products that can have different physiological roles and toxicity, particularly when the substrate of the hydrolytic processes are neuronal peptides and proteins highly related to neurodegeneration. We report a hydrolytic study performed with the HPLC-MS technique at different temperatures (4 °C and 37 °C) on peptide fragments of different neuronal proteins (amyloid-β, tau, and α-synuclein) in physiological conditions in the presence of Cu2+ and Zn2+ ions, two metal ions found at millimolar concentrations in amyloid plaques. The coordination of these metal ions with these peptides significantly protects their backbones toward hydrolytic degradation, preserving the entire sequences over two weeks in solution, while the free peptides in the same buffer are fully fragmented after the same or even shorter incubation period. Our data show that peptide cleavage is not only ruled by the chemical sensitivity of amino acids, but the peptide conformation changes induced by metal coordination influence hydrolytic reactions. The enhanced stability of neuronal peptides provided by metal coordination can increase local levels of amyloidogenic species capable of seeding fibril growth, resulting in aberrant protein depositions and deficits in neuronal activity.

Elucidation of Mg2+ induced size and charge heterogeneity in monoclonal antibody therapeutics

Changes in charge variant profile are known to affect mAb stability and vice versa. This report elucidates the effects of magnesium metal (0.5 mM Mg2+) on trastuzumab (IgG1 antibody). Mg2+ is often used as an excipient (50-100 mM) and lubricant (5-10 % w/w) in biopharmaceutical formulations. Analytical size-exclusion chromatography (SEC) and cation-exchange chromatography (CEX) coupled with mass spectrometry (MS) were used to evaluate the size and charge heterogeneity in the thermal and metal stressed samples and compared to the control sample (room temperature). The present study unveils that presence of Mg2+ significantly increases the rate of aggregation with 9 % aggregation observed in Mg2+ stressed samples as compared to that from thermal stress (~2 %) or control sample (<1 %). Similarly, a 2-fold elevation in acidic variants was observed both in presence of Mg2+ and thermal stress, when contrasted with the control sample. Application of stress also led to the formation of 17 additional chemical modifications (7 due to thermal stress and 10 due to Mg2+ stress) which were not identified in control, predominantly involving deamidation, isomerization of aspartic acid, oxidation, and succinimide modifications. The results indicate the need for a detailed analysis of the impact of presence of metals in biotherapeutic formulations.

M2e-Derived Peptidyl and Peptide Amphiphile Micelles as Novel Influenza Vaccines

Background: A significant problem with current influenza vaccines is their reliance on predictions of the most prevalent strains for the upcoming season, with inaccurate forecasts greatly reducing the overall efficacy of the immunization campaign. A universal influenza vaccine, which leverages epitopes conserved across many, if not all, strains of influenza, could reduce the need for extremely accurate forecasting. The highly conserved ectodomain of the influenza M2 protein contains a B cell epitope in the M22-16 region, making it a promising candidate as a universal influenza vaccine. Unfortunately, free peptide antigens alone are limited as vaccines due to their poor stability and weak immunogenicity in vivo. To improve the potential of peptide vaccines, immunostimulatory micellar nanoparticles can be generated from them by lipid conjugation (i.e., peptide amphiphiles-PAs). Methods: M22-16 peptides and Palm2K-M22-16-(KE)4 PAs were synthesized and characterized. BALB/c mice were subcutaneously vaccinated with these formulations, and ELISAs were conducted on serum collected from the vaccinated mice to evaluate induced antibody responses. Results: Unlike other peptide antigens previously studied, the unmodified M22-16 peptide micellized without any peptidyl or lipid modifications. M22-16 peptidyl micelles (PMs) were spherical with largely undefined secondary structure somewhat different from the cylindrical, β-sheet-containing Palm2K-M22-16-(KE)4 peptide amphiphile micelles (PAMs). Differences in physical properties were found to correlate with slightly different immune responses with PAMs eliciting higher antibody titers after the initial immunization, whereas both micelle types elicited strong IgG titers after a prime-boost regimen. Conclusions: These results suggest the viability of PAMs as single-dose vaccines, while both PMs and PAMs show potential using a multi-dose immunization approach.

A Comprehensive Study on the Amino Acids and Tryptophan-Derived Molecules in Iberian Wine Vinegar

Wine vinegar, valued for its ancient origins and culinary versatility, has garnered scientific interest due to its complex composition and potential health benefits. This study aims to explore the nutritional and bioactive properties of different wine vinegars, focusing on their amino acid content, particularly tryptophan-derived molecules such as serotonin and melatonin. White wine vinegar, red wine vinegar, port wine vinegar, and balsamic vinegar from the Douro and Rioja regions were analyzed using high-performance liquid chromatography and solid-phase extraction (HPLC-SPE). The study examined the amino acid profiles and the presence of serotonin and melatonin across the samples. The analysis revealed the presence of significant bioactive amino acids, including arginine (found in sample 059 at 61.21 mmol/L), alanine (in a concentration of 30.33 mmol/L in sample 209), and threonine (sample 336 presented the highest concentration-71.47 mmol/L), which have been linked to cardiovascular health, immune system support, and mucosal regulation. The amino acid content varied among the vinegar types, with slower acetification and prolonged aging reducing their concentrations. Tryptophan was mainly found in sample 059 (30.54 mmol/L). These findings, with their potential to influence the scientific community's understanding of the health-promoting properties of wine vinegar, particularly its amino acid content and the potential influence of production processes on bioactive molecules, are of great interest.

Hybrid Diffusion Model for Stable, Affinity-Driven, Receptor-Aware Peptide Generation

The convergence of biotechnology and artificial intelligence has the potential to transform drug development, especially in the field of therapeutic peptide design. Peptides are short chains of amino acids with diverse therapeutic applications that offer several advantages over small molecular drugs, such as targeted therapy and minimal side effects. However, limited oral bioavailability and enzymatic degradation have limited their effectiveness. With advances in deep learning techniques, innovative approaches to peptide design have become possible. In this work, we demonstrate HYDRA, a hybrid deep learning approach that leverages the distribution modeling capabilities of a diffusion model and combines it with a binding affinity maximization algorithm that can be used for de novo design of peptide binders for various target receptors. As an application, we have used our approach to design therapeutic peptides targeting proteins expressed by Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) genes. The ability of HYDRA to generate peptides conditioned on the target receptor's binding sites makes it a promising approach for developing effective therapies for malaria and other diseases.

Origami of KR-12 Designed Antimicrobial Peptides and Their Potential Applications

This review describes the discovery, structure, activity, engineered constructs, and applications of KR-12, the smallest antibacterial peptide of human cathelicidin LL-37, the production of which can be induced under sunlight or by vitamin D. It is a moonlighting peptide that shows both antimicrobial and immune-regulatory effects. Compared to LL-37, KR-12 is extremely appealing due to its small size, lack of toxicity, and narrow-spectrum antimicrobial activity. Consequently, various KR-12 peptides have been engineered to tune peptide activity and stability via amino acid substitution, end capping, hybridization, conjugation, sidechain stapling, and backbone macrocyclization. We also mention recently discovered peptides KR-8 and RIK-10 that are shorter than KR-12. Nano-formulation provides an avenue to targeted delivery, controlled release, and increased bioavailability. In addition, KR-12 has been covalently immobilized on biomaterials/medical implants to prevent biofilm formation. These constructs with enhanced potency and stability are demonstrated to eradicate drug-resistant pathogens, disrupt preformed biofilms, neutralize endotoxins, and regulate host immune responses. Also highlighted are the safety and efficacy of these peptides in various topical and systemic animal models. Finaly, we summarize the achievements and discuss future developments of KR-12 peptides as cosmetic preservatives, novel antibiotics, anti-inflammatory peptides, and microbiota-restoring agents.

BrSPR-20-P1 peptide isolated from Brevibacillus sp. developed into liposomal hydrogel as a potential topical antimicrobial agent

A novel BrSPR-20-P1 antimicrobial peptide (P1-AMP; NH2-VVVNVLVKVLPPPVV-COOH) isolated from Brevibacillus sp. SPR-20 was encapsulated in a liposome containing varying proportions of l-α-phosphatidylcholine (PC) and cholesterol (CH). P1-AMP liposomes were incorporated into a chitosan hydrogel to achieve a peptide concentration of 0.02%. P1-AMP has been tested for its antibacterial and in vitro wound healing activities. The physicochemical characteristics of liposomes and hydrogel were investigated, including in vitro drug release, permeability, cell toxicity, antimicrobial activities, and stability studies. P1-AMP showed higher antimicrobial and wound-healing activities than the negative control. A toxicity test of P1-AMP in keratinocyte cell lines revealed cell viability of 100% at a concentration range of 1.96-1000 μg mL-1. The empty liposomes exhibited an average particle size ranging from 324.5 ± 8.6 to 1823.7 ± 288.2 nm. The size range of P1-AMP liposomes was 378.6 ± 14.0 to 2363.0 ± 255.6 nm. The zeta potential of the blank liposome ranged from -40.43 ± 2.51 to -60.17 ± 0.93 mV and it decreased to -57.33 ± 0.72 to -70.33 ± 0.15 mV of the liposome loaded with peptide. SEM images showed liposomes were ovoid spheres with smooth surfaces. The chosen formulation, composed of PC to CH in an 18 : 1 ratio (formulation F3), had the highest entrapment effectiveness with small particle size and possessed an acceptable zeta potential. The developed P1-AMP liposome-loaded hydrogels exhibited a yellowish-clear appearance with a viscosity of 758.0 ± 149.8 cPs. The P1-AMP was rapidly released from the P1-AMP-loaded liposome hydrogel formulation. The P1-AMP-loaded liposome showed high permeability compared to P1-AMP alone or P1-AMP in hydrogel without the incorporation of liposomes. The minimum inhibitory concentration (MIC) against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) of P1-AMP-loaded liposome hydrogel was 2 μg mL-1, equivalent to P1-AMP. It completely killed S. aureus at 10× and 5× MIC after 6 and 12 h of incubation, respectively. The formulation did not induce cytotoxicity to the tested keratinocyte cell and remained stable for at least 6 months under the studied conditions.

Fisetin-loaded pluronic-based nanogel: Radiation synthesis for alleviating neurocognitive impairments in a rat model of alzheimer's disease via modulation of the apoptotic cascade

Alzheimer's disease (AD) is a neurodegenerative disorder marked by cognitive impairment and memory loss. In this study, AD was experimentally induced in rats using aluminum chloride (AlCl3) and D-galactose (D-gal). Fisetin (Fis), a natural compound with antioxidant and anti-inflammatory properties, has potential for neurodegeneration management, but its low bioavailability limits clinical applications. To address this, we synthesized and characterized Pluronic-2-Acrylamido-2-methylpropane sulfonic acid (PLUR-PAMPS) nanogels using gamma radiation and successfully loaded Fis onto them (Fis-PLUR-PAMPS). The optimal formulation exhibited minimal particle size, a highly acceptable polydispersity index, and the highest zeta-potential, enhancing stability and solubilization efficiency. Our goal was to improve Fis's bioavailability and assess its efficacy against AlCl3/D-gal-induced AD. Male albino Wistar rats were pre-treated orally with Fis (40 mg/kg) or Fis-PLUR-PAMPS for seven days, followed by a seven-day intraperitoneal injection of AlCl3 and D-gal. Behavioral assessments, histopathological analysis, and biochemical evaluation of markers related to AD pathology were conducted. Results demonstrated that Fis-PLUR-PAMPS effectively mitigated cognitive impairments and neurodegenerative signs induced by AlCl3/D-gal. These findings suggest that Fis-PLUR-PAMPS nanogels enhance Fis's bioavailability and therapeutic efficacy, offering a promising approach for AD management.

Comparative understanding of peroxide quantitation assays: a case study with peptide drug product degradation

Peroxide-mediated oxidation of drug molecules is a known challenge faced throughout the pharmaceutical development pathway-from early-stage stability studies to manufacturing processes. During the initial development stage, the major source of peroxide is the formulation excipients, whether they are pre-loaded or generated in situ due to slow degradation, and in the late phase, peroxides can be introduced during sanitization processes or generated via cavitation. In essence, a control strategy for peroxide mitigation often becomes a critical quality attribute for successful drug development. To this end, quantitation of peroxide is essential to monitor the peroxide level to ensure product quality and proposed shelf-life. However, methods for reliable and robust quantitation to detect trace levels of peroxide in a complex drug product matrix become increasingly challenging. This article discusses three high-throughput assays based on absorbance, fluorescence and chemiluminescence measurements to detect peroxide at a low level and compares the methods through validation studies in water. Selected methods have also been tested to understand the forced degradation of model peptide drug products with spiked hydrogen peroxide. Peptide degradation profiles and residual peroxide levels are presented to provide an understanding of the suitability of the quantitation methods and their performance.

Stability and expression of K-ras mimotopes in freeze-dried recombinant Lactococcus lactis NZ3900-fermented milk powder during storage in vacuum packaging

AIMS

This study aims to evaluate the storage stability of the freeze-dried recombinant Lactococcus lactis NZ3900-fermented milk powder expressing K-ras (Kristen rat sarcoma viral oncogene homolog) mimotopes targeting colorectal cancer in vacuum packaging.

METHODS AND RESULTS

The freeze-dried L. lactis-fermented milk powder stored in 4-ply retortable polypropylene (RCPP)-polyamide (PA)-aluminium (AL)-polyethylene terephthalate (PET) and aluminium polyethylene (ALPE) was evaluated throughout 49 days of accelerated storage (38°C and 90% relative humidity). The fermented milk powder stored in 4-ply packaging remained above 6 log10 CFU g-1 viability, displayed lower moisture content (6.1%), higher flowability (43° angle of repose), water solubility (62%), and survivability of L. lactis after simulated gastric and intestinal digestion (>82%) than ALPE packaging after 42 days of accelerated storage. K-ras mimotope expression was detected intracellularly and extracellularly in the freeze-dried L. lactis-fermented milk powder upon storage.

CONCLUSIONS

This suggests that fermented milk powder is a suitable food carrier for this live oral vaccine.

Development and Evaluation of a Water-Free In Situ Depot Gel Formulation for Long-Acting and Stable Delivery of Peptide Drug ACTY116

In situ depot gel is a type of polymeric long-acting injectable (pLAI) drug delivery system; compared to microsphere technology, its preparation process is simpler and more conducive to industrialization. To ensure the chemical stability of peptide ACTY116, we avoided the use of harsh conditions such as high temperatures, high shear mixing, or homogenization; maintaining a water-free and oxygen-free environment was also critical to prevent hydrolysis and oxidation. Molecular dynamics (MDs) simulations were employed to assess the stability mechanism between ACTY116 and the pLAI system. The initial structure of ACTY116 with an alpha helix conformation was constructed using SYBYL-X, and the copolymer PLGA was generated by AMBER 16; results showed that PLGA-based in situ depot gel improved conformational stability of ACTY116 through hydrogen bonds formed between peptide ACTY116 and the components of the pLAI formulation, while PLGA (Poly(DL-lactide-co-glycolide)) also created steric hindrance and shielding effects to prevent conformational changes. As a result, the chemical and conformational stability and in vivo long-acting characteristics of ACTY116 ensure its enhanced efficacy. In summary, we successfully achieved our objective of developing a highly stable peptide-loaded long-acting injectable (LAI) in situ depot gel formulation that is stable for at least 3 months under harsh conditions (40 °C, above body temperature), elucidating the underlying stabilisation mechanism, and the high stability of the ACTY116 pLAI formulation creates favourable conditions for its in vivo pharmacological activity lasting for weeks or even months.

The Development of a Stable Peptide-Loaded Long-Acting Injection Formulation through a Comprehensive Understanding of Peptide Degradation Mechanisms: A QbD-Based Approach

Quality by design (QbD) serves as a systematic approach to pharmaceutical development, beginning with predefined objectives and emphasizing an understanding of the product based on sound science and risk management. The purpose of this study is to utilize the QbD concept to develop a stable peptide-loaded long-acting injection formulation. An in-depth comprehension of peptide degradation mechanisms was achieved through forced degradation investigations, elucidating (acid) hydrolysis and oxidation as the primary degradation pathways for the peptide ACTY116. The quality built into the product was focused on risk assessment, for which the critical material attributes (CMAs) and critical process parameters (CPPs) associated with the critical quality attributes (CQAs) of each formulation were identified, leading to the development of the corresponding control strategies. CQAs for three LAI (long-acting injectable) formulations were enhanced by taking the right control strategies. The LAI formulation exhibiting the highest stability for ACTY116 was chosen for subsequent pharmacokinetic investigations in rats. The objective of addressing peptide chemical instability and in vivo long-acting release was achieved. For other molecules with susceptible functionalities like amide bonds, amino groups, and hydroxyl groups, the utilization of PLGA-based in situ gel as an LAI formulation for stabilizing molecules provides valuable insights.

Isolation and Purification of Protamine from the Cultured Takifugu flavidus and Its Physicochemical Properties

Protamine is a cationic peptide derived from fish sperm and has several important functional properties: antibacterial properties, acting as a carrier for injectable insulin and as a heparin antagonist, combatting fatigue, etc. Thus, it has been widely used in medicinal applications and food products. Cultured Takifugu flavidus is a type of pufferfish with a delicious taste that is popular in China, and its production is increasing significantly. Therefore, protamine was extracted via acid extraction from the sperm of Takifugu flavidus and further isolated and purified via sephadex gel chromatography, ion exchange chromatography, and desalination chromatography. Furthermore, the physicochemical properties of protamine were investigated. The results showed that the sperm of the cultured T. flavidus were non-toxic, and the extracted and purified protamine had high contents of arginine (36.90%) and lysine (27.02%), respectively. The secondary structure of protamine was mainly β-folded and irregularly curled. Additionally, protamine exhibited high thermal stability with a denaturation temperature of 176 °C. This study would provide a theoretical basis for the structural analysis, bioactivity, and resource development of pufferfish protamine and help to promote the development of the pufferfish industry.

A New Approach for Preparing Stable High-Concentration Peptide Nanoparticle Formulations

The subcutaneous administration of therapeutic peptides would provide significant benefits to patients. However, subcutaneous injections are limited in dosing volume, potentially resulting in high peptide concentrations that can incur significant challenges with solubility limitations, high viscosity, and stability liabilities. Herein, we report on the discovery that low-shear resonant acoustic mixing can be used as a general method to prepare stable nanoparticles of a number of peptides of diverse molecular weights and structures in water without the need for extensive amounts of organic solvents or lipid excipients. This approach avoids the stability issues observed with typical high-shear, high-intensity milling methods. The resultant peptide nanosuspensions exhibit low viscosity even at high concentrations of >100 mg/mL while remaining chemically and physically stable. An example nanosuspension of cyclosporine nanoparticles was dosed in rats via a subcutaneous injection and exhibited sustained release behavior. This suggests that peptide nanosuspension formulations can be one approach to overcome the challenges with high-concentration peptide formulations.

Influence of Fatty Acid Modification on the Anticancer Activity of the Antimicrobial Peptide Figainin 1

Antimicrobial peptides derived from the skin secretions of amphibians have made important progress in tumor therapy due to their unique mechanism of destroying cell membranes. Figainin 1 (F1) is an 18-amino acid antimicrobial peptide from the skin secretions of Boana raniceps frogs. In a previous study, F1 was shown to inhibit cancer cell proliferation. F1 is composed entirely of natural amino acids; therefore, it is easily degraded by a variety of proteases, resulting in poor stability and a short half-life. In the present study, we used a fatty acid modification strategy to improve the stability of Figainin 1. Among the 8 peptides synthesized, A-10 showed the strongest antiproliferative activity against K562 cells and the other four tumor cell lines, and its stability against serum and proteinase K was improved compared with F1. We found that A-10 works through two mechanisms, cell membrane destruction and apoptosis, and can arrest the cell cycle in the G0/G1 phase. Moreover, A-10 exhibited self-assembly behavior. Overall, it is necessary to select a fatty acid with a suitable length for modification to improve the stability and antiproliferative activity of antimicrobial peptides. This study provides a good reference for the development of antimicrobial peptides as effective anticancer compounds.

Sialylation: An alternative to designing long-acting and targeted drug delivery system

Long-acting and specific targeting are two important properties of excellent drug delivery systems. Currently, the long-acting strategies based on polyethylene glycol (PEG) are controversial, and PEGylation is incapable of simultaneously possessing targeting ability. Thus, it is crucial to identify and develop approaches to produce long-acting and targeted drug delivery systems. Sialic acid (SA) is an endogenous, negatively charged, nine-carbon monosaccharide. SA not only mediates immune escape in the body but also binds to numerous disease related targets. This suggests a potential strategy, namely "sialylation," for preparing long-acting and targeted drug delivery systems. This review focuses on the application status of SA-based long-acting and targeted agents as a reference for subsequent research.