Antimicrobial peptides are promising candidates for anti-infective pharmaceuticals. Unfortunately, because of their low proteolytic and chemical stability, their usage is generally narrowed down to topical formulations. Until now, numerous approaches to increase peptide stability have been proposed. One of them, peptide hydrocarbon stapling, a modification based on stabilizing peptide secondary structure with a side-chain covalent hydrocarbon bridge, have been successfully applied to many peptides. Moreover, constraining secondary structure of peptides have also been proven to increase their biological activity. This review article describes studies on hydrocarbon stapled antimicrobial peptides with respect to improved drug-like properties.

AT-cut quartz crystals vibrating in the thickness-shear mode (TSM), especially quartz crystal resonators (QCRs), are well known as very efficient mass sensitive systems because of their sensitivity, accuracy, and biofunctionalization capacity. They are highly reliable in the measurement of the mass of deposited samples, in both gas and liquid matrices. Moreover, they offer real-time monitoring, as well as relatively low production and operation costs. These features make mass sensitive systems applicable in a wide range of different applications, including studies on protein and peptide primary packaging, formulation, and drug product manufacturing process development. This review summarizes the information on some particular implementations of quartz crystal microbalance (QCM) instruments in protein and peptide drug product development as well as their future prospects.

Peptides and proteins constitute a large group of molecules that play multiple functions in living organisms. In conjunction with their important role in biological processes and advances in chemical approaches of synthesis, the interest in peptide-based drugs is still growing. As the side chains of amino acids can be basic, acidic, or neutral, the peptide drugs often occur in the form of salts with different counter-ions. This review focuses on the role of counter-ions in peptides. To date, over 60 peptide-based drugs have been approved by the FDA. Based on their area of application, biological activity, and results of preliminary tests they are characterized by different counter-ions. Moreover, the impact of counter-ions on structure, physicochemical properties, and drug formulation is analyzed. Additionally, the application of salts as mobile phase additives in chromatographic analyses and analytical techniques is highlighted.

Antimicrobial peptides (AMPs) are compounds widely distributed in nature that display activity against a broad spectrum of pathogens. Amphibian skin, as an organ rich in pharmacologically active peptides, appears to be an interesting source of novel AMPs. Aurein 1.2 (GLFDIIKKIAESF-NH₂) is a short 13-residue antimicrobial peptide primarily isolated from the skin secretions of Australian bell frogs. In this study, the alanine scan of aurein 1.2 was performed to investigate the effect of each amino acid residue on its biological and physico-chemical properties. The biological studies included determination of minimum inhibitory concentration, activity against biofilm, and inhibitory effect on its formation. Moreover, the hemolytic activity as well as serum stability was determined. The hydrophobicity of peptides and their self-assembly were investigated using reversed-phase chromatography. In addition, their helicity was calculated from circular dichroism spectra. The results not only provided information on structure-activity relationship of aurein 1.2 but also gave insights into design of novel analogs of AMPs in the future.

Various opioids are added to local anesthetic solutions for spinal anesthesia. This may change the final density of the local anestetic (LA) mixture. This effect regarding current concepts in spinal anesthesia needs to be re-evaluated. In order to re-evaluate such effects, hyperbaric and isobaric local anesthetic (LA) solutions were mixed with opioid adjuvants (A) using the equipment available in the operating room. Ten density measurements for each composition (LA-A) were performed. The density change of 0.0006 g/mL was regarded as significant. Measured densities were also compared with theoretical values calculated using Hare’s. As a result, the addition of an opioid adjuvant caused a significant reduction in the final density of the LA-A solution. In hyperbaric LA mixtures, it did not change the baricity from hyperbaric to isobaric. However, the addition of highly hypobaric fentanyl 0.99360 g/mL (SD ± 0.00004) changes all isobaric LA solutions baricity to hypobaric. The comparison of measured and theoretical densities revealed significant differences (p > 0.05). However, the absolute reduction reached 0.0006 g/mL in only two LA-A compositions. We conclude that the addition of fentanyl to isobaric LA results in a hypobaric solution that may affect the distribution of the block. The inadequacy of LA-A in a clinical setting is unlikely to influence block characteristics.

Biopharmaceutical medicines represent one of the most dynamic sectors of the pharmaceutical industry, with therapeutic proteins forming the largest and most important group. Their structural complexity and inherent sensitivity to chemical and physical stressors, however, continue to pose major challenges for formulation development and long-term stability. Short peptides have emerged as a promising yet underutilized class of excipients for protein-based drug products. Their modular architecture allows for precise tuning of physicochemical properties such as polarity, charge distribution, and hydrogen-bonding potential, thereby offering advantages over single amino acids. Experimental studies indicate that short peptides can serve multiple functions: stabilizers, antioxidants, viscosity-lowering agents, and as lyo/cryoprotectants or bulking agents in lyophilized formulations. Notably, the relatively small and chemically defined space of short peptides—approximately 400 possible dipeptides and 8000 tripeptides—makes them particularly amenable to systematic screening and computational modeling. This enables rational identification of candidates with tailored excipient functions. This review summarizes current knowledge on the use of short peptides as excipients in parenteral protein formulations, with a focus on their functional versatility and potential for rational design in future development.