Research progress in the role and mechanism of Leucine in regulating animal growth and development

Plant proteins and peptides as key contributors to good health: A focus on pulses

The growing interest of the public in healthy food products with adequate nutritional quality has triggered a search for novel sources of protein. This review discusses scientific evidence on the available sources, processing, and biological properties of plant-based protein and bioactive peptides, with a particular emphasis on pulses, as these are some of the most important sources of protein and peptides displaying a wide range of health benefits. Processing plant-based proteins and derived peptides require standardized methods ensuring the improvement of their nutritional quality to counteract limiting factors affecting their evenness to other protein sources. If protein and bioactive peptides can be produced as functional ingredients, the industry releases patents, making them highly marketable to develop functional food products. Current research supports that plant-based food products constitute a nutritious part of a healthy diet by preventing chronic non-communicable diseases, but more studies, particularly clinical trials, are needed to demonstrate these effects fully.

Nonessential amino acid is not nonessential in geriatric patients: implications for maxillofacial wound healing and bone repair

BACKGROUND

Nonessential amino acids (NEAAs) are traditionally regarded as dispensable because they can be synthesized endogenously from glucose-derived intermediates. Emerging evidence, however, shows that the capacity for de novo NEAA biosynthesis declines in aged tissues, rendering several of these molecules conditionally essential during periods of stress such as surgery or fracture repair.

MAIN BODY

In the cranio-maxillofacial arena - where bone and soft-tissue regeneration must occur in an environment already compromised by osteoporosis, multimorbidity, and restricted oral intake - insufficient NEAA supply may translate into delayed union, wound dehiscence, and heightened infection risk. This narrative review integrates biochemical, preclinical, and clinical data to map age-dependent changes in the serine/glycine, glutamine/glutamate, arginine/citrulline, cysteine/trans-sulfuration, and alanine cycles, examines their impact on osteogenesis and mucosal healing, and evaluates nutritional or pharmacological strategies to restore NEAA sufficiency. Particular attention is paid to serine-one-carbon metabolism, the intestinal-renal arginine axis, and redox-sensitive cysteine pathways, all of which are intimately linked to collagen deposition, osteoblast differentiation, and immune modulation.

CONCLUSION

We conclude that proactive optimization of NEAA status - through targeted supplementation or metabolic activation - represents a low-risk, biologically rational adjunct to enhance postoperative outcomes in geriatric maxillofacial patients.

Low, Intermediate, and High Glutamine Levels Are Progressively Associated with Increased Lymphopenia, a Diminished Inflammatory Response, and Higher Mortality in Internal Medicine Patients with Sepsis

Background: The pathophysiological mechanisms underlying altered plasma glutamine concentrations in sepsis remain poorly understood. Identifying clinical, immunological, and metabolic correlates of glutamine fluctuations is crucial to advancing precision medicine, developing targeted therapies, and improving survival outcomes in septic patients. Methods: We enrolled 469 patients with sepsis and assessed inflammatory markers-including body temperature, white blood cell count, and C-reactive protein levels-upon admission to the internal medicine unit. Lymphocyte count and plasma concentrations of glutamine, glutamic acid, 5-oxoproline, phenylalanine, tyrosine, and leucine were measured using gas chromatography-mass spectrometry. Patients were stratified into three groups based on plasma glutamine levels. Mortality was recorded at 30 days and 6 months. Results: Low, intermediate, and high glutamine levels were observed in 46% (n = 217), 47% (n = 218), and 7% (n = 34) of patients, respectively. Patients with hyperglutaminemia exhibited significantly lower body temperature, white blood cell and lymphocyte counts, C-reactive protein levels, and glutamic acid-to-5-oxoproline ratio (a surrogate marker of glutathione availability), along with elevated phenylalanine levels, leucine levels, and tyrosine-to-phenylalanine ratio (all p < 0.01). Metabolic disruption and mortality increased progressively across glutamine level groups. Kaplan-Meier analysis demonstrated significantly higher mortality in patients with elevated glutamine levels at both 30 days (log-rank p = 0.03) and 6 months (log-rank p = 0.05). Conclusions: At baseline, increasing plasma glutamine levels are associated with progressively deeper lymphopenia, more pronounced metabolic derangement, and higher short- and long-term mortality in patients with sepsis.

Effects of dietary Leucine supplementation on intestinal development and gene expression of pattern recognition receptors (PRRs) in broilers

This study investigated the effects of 0.4 % Leucine (Leu) addition on growth performance, intestinal growth, carcass characteristics, and pattern recognition receptors (PRR) gene expression in broilers. A Total of 144 one-day-old Arbor Acres broilers were randomly divided into two treatment groups: the basal diet (CON) and the basal diet added with 0.4 % crystalline Leu. Growth performance, visceral organ indices, carcass traits, intestinal growth, and mRNA levels of TLR2, TLR4, NOD1, NOD5, and IL-4 were analyzed at 20 and 40 d. Results indicated that Leu reduced the FCR during 1-20 d (P < 0.05) and increased ADG during 21-40 d (P < 0.05). Leu increased IL-4 expression in the duodenum and jejunum and enhanced relative intestinal weight and length during the starting phase (20 d) (P < 0.05). Leu downregulated the gene expression of NOD1, NOD5, and TLR4 in the duodenum (P < 0.05) and reduced the jejunal mRNA levels of NOD1 (P < 0.05). At 40 d, Leu increased pectoral muscle yield and downregulated TLR4 in pectoral muscle (P < 0.05). These findings suggest that dietary Leu supplementation improves intestinal development and modulates PRR-related immune responses in a tissue-specific manner, highlighting its potential as an immunomodulatory feed additive.

Fermentation of Pediococcus pentosaceus JC30 Improves Phytochemical, Flavor Characteristics and Antioxidant Activity of Mulberry Leaves

Mulberry leaves contain polysaccharides, phenols, alkaloids, and other active ingredients which have medicinal and edible value. In this study, fermented mulberry leaf powder was prepared by solid-state fermentation using Pediococcus pentosaceus JC30. The effects of the fermentation on the phytochemical, flavor characteristics, phenolics, and antioxidant activity of mulberry leaves were studied. The results showed that the content of γ-aminobutyric acid in fermented mulberry leaf powder (FMLP) increased by 6.73-fold and the content of phytic acid decreased by 11.16%. Ultra-high-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) analysis showed that the fermentation of Pediococcus pentosaceus JC30 altered the phenolic composition of mulberry leaves, increasing the total free phenolic content by 88.43%. In particular, the contents of free phenols such as leucocyanidin, myricetin, and quercetin increased significantly and were positively correlated with antioxidant capacity. The fermentation of Pediococcus pentosaceus JC30 significantly enhanced the scavenging ability of DPPH free radicals, hydroxyl radicals, and the total reducing ability of mulberry leaves. Gas chromatography ion mobility spectrometry (GC-IMS) analysis showed that FMLP has an intense fruity and floral aroma, while having less grassy and earthy odor. The fermentation improved the phytochemical, flavor, and nutritional value of mulberry leaves, which provides more possibilities for the development of mulberry leaf products outside the sericulture industry.

Ultrasound-Assisted Deep Eutectic Solvent Extraction of Antioxidant and Anti-Colorectal Cancer Proteins from Spirulina Biomass: Process Intensification, Characterization, and Bioactivity Evaluation

Spirulina, a cyanobacterial biomass, is renowned for its high protein content and bioactive compounds, making it a promising candidate for health-promoting applications. This study explores the ultrasound-assisted deep eutectic solvent (DES) extraction technique for isolating antioxidants and anticancer proteins from Spirulina biomass, aiming to enhance extraction efficiency and preserve protein bioactivity. The extraction process was optimized using response surface methodology (RSM), varying parameters such as biomass concentration, sonication amplitude, and extraction duration. The optimized extraction conditions-5% biomass concentration, 40% sonication amplitude, and 22-minute extraction-achieved a high protein yield of 80.62%, with a protein concentration of 442.88 mg/g extract and an essential amino acid content of 39.91%. The extracted proteins exhibited remarkable bioactivity, including strong antioxidant properties, with 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of 0.25 mg GAE/g, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activity of 0.58 mg TE/g, and ferric reducing antioxidant power (PFRAP) of 9.63 mg gallic acid equivalent (GAE)/g. Additionally, the protein extract displayed selective cytotoxicity against colorectal cancer cell lines, with half-maximal inhibitory concentration (IC50) values of 10.25 mg/mL for Caco-2 and 15.40 mg/mL for HT-29 cells, while maintaining low toxicity towards normal Vero cells. Apoptosis rates of 70.43% in Caco-2 and 51.33% in HT-29 cells further confirm the anticancer potential of the extract. The functional properties of the extracted protein, including high foaming capacity (100%), emulsifying capacity (94.05%), and digestibility (85.77%), underscore its potential for diverse applications in food, pharmaceutical, and nutraceutical industries. This eco-friendly and efficient extraction approach aligns with sustainable development goals and offers a viable strategy for harnessing Spirulina's bioactive potential.

Defatted chia (Salvia hispanica L.) flour peptides: Exploring nutritional profiles, techno-functional and bio-functional properties, and future directions

Chia (Salvia hispanica L.) is a summer-blooming herb from the mint family, known for its rich nutritional profile, including high-quality protein, fibre, and a balanced ratio of omega-3 and omega-6 fatty acids. With the rising demand for chia oil, defatted chia flour (DCF), a by-product of oil extraction, has gained attention as a valuable ingredient. DCF is rich in essential macronutrients and amino acids, offering a sustainable alternative to traditional protein sources and supporting global food sustainability and waste reduction efforts. Recent studies have highlighted the techno-functional properties of DCF peptides, showing excellent solubility, water- and oil-absorption capacities, as well as emulsifying, foaming, and gelling abilities. These properties enhance their application in diverse food systems, making DCF an important ingredient in the development of nutritious, innovative, and appealing food products. Beyond their functional roles, chia-derived peptides also exhibit significant bioactive properties, such as antioxidants, antihypertensive, anti-inflammatory, neuroprotective, antidiabetic, antimicrobial, anti-aging, hypolipidemic, and hypoglycaemic effects. These properties make them beneficial for improving health and wellness. Integrating DCF peptides into food products provides a natural approach to managing chronic diseases, promoting longevity, and improving overall health. To fully realize the potential of DCF peptides, future research should focus on understanding their bioactivities at the molecular level and exploring how they interact with various physiological systems. Interdisciplinary collaboration among food science, biotechnology, pharmacology, and nutrition is essential, along with careful evaluation of safety and potential risks. Regulatory frameworks will be crucial for the broader use of DCF peptides in food and nutraceuticals. Additionally, advancements in peptide production, extraction, and purification technologies will be necessary for large-scale, sustainable applications. Focusing on these areas will maximize the benefits of chia peptides for human health, nutrition, and environmental sustainability.

Characterisation of intestinal amino acid and oleic acid absorption and their interaction in the Pacific spiny dogfish (Squalus suckleyi)

Elasmobranchs are commonly carnivores and are important in energy transfer across marine ecosystems. Despite this, relatively few studies have examined the physiological underpinnings of nutrient acquisition in these animals. Here, we investigated the mechanisms of uptake at the spiral valve intestine for two representative amino acids (L-alanine, L-leucine) and one representative fatty acid (oleic acid), each common to the diet of a carnivore, the Pacific spiny dogfish (Squalus suckleyi). Transport was saturable for all three nutrients, depending upon transport calculation metric (i.e., mucosal disappearance, serosal appearance, or tissue accumulation). Over 0-10 mM range of amino acids the concentration at which ½ maximal transport occurred (Km; a measure of transporter affinity) was 11.9 and 11.2 mM for tissue accumulation of alanine and leucine, respectively. Oleic acid transport was measured at lower concentrations (0-200 µM) and tissue accumulation did not reach saturation. Putative amino acid transport systems were delineated upon confirmation of sodium dependence and competitive inhibition with threonine, glycine, and lysine. The interplay of nutrient combinations on the modulation of nutrient acquisition rates, which better mimics the complex composition of both a meal and the internal osmolytes, was next investigated. Here, the application of serosal oleic acid led to diminished mucosal disappearance of leucine. Feeding did not significantly alter transport rates, perhaps indicative of maximal transport of these energy sources whenever the substrate is available given their importance both as metabolic fuels and precursors to the osmolyte urea.

Dileucine ingestion, but not leucine, increases lower body strength and performance following resistance training: A double-blind, randomized, placebo-controlled trial

BACKGROUND

The essential amino acid leucine (LEU) plays a crucial role in promoting resistance-training adaptations. Dileucine (DILEU), a LEU-LEU dipeptide, increases MPS rates, however its impact on resistance training outcomes remains unexplored. This study assessed the effects of DILEU supplementation on resistance training adaptations.

METHODS

Using a randomized, double-blind, placebo-controlled approach, 34 resistance-trained males (age: 28.3 ± 5.9 years) consumed 2 grams of either DILEU monohydrate (RAMPS™, Ingenious Ingredients, L.P.), LEU, or placebo (PLA) while following a 4-day per week resistance training program for 10 weeks. Changes in body composition, 1-repetition maximum (1RM) and repetitions to failure (RTF) for leg press (LP) and bench press (BP), anaerobic capacity, countermovement jump (CMJ), and maximal voluntary contraction (MVC) were assessed after 0 and 10 weeks.

RESULTS

Significant main effects for time (p < 0.001) were realized for LP and BP 1RM and RTF. A significant group × time interaction was identified for changes in LP 1RM (p = 0.02) and LP RTF (p = 0.03). Greater increases in LP 1RM were observed in DILEU compared to PLA (p = 0.02; 95% CI: 5.8, 73.2 kg), and greater increases in LP RTF in DILEU compared to LEU (p = 0.04; 95% CI: 0.58, 20.3 reps). No significant differences were found in other measures.

CONCLUSIONS

DILEU supplementation at 2 grams daily enhanced lower body strength and muscular endurance in resistance-trained males more effectively than LEU or PLA. These findings suggest DILEU as a potentially effective supplement for improving adaptations to resistance training. NCT06121869 retrospectively registered.

Primary Roles of Branched Chain Amino Acids (BCAAs) and Their Metabolism in Physiology and Metabolic Disorders

Leucine, isoleucine, and valine are collectively known as branched chain amino acids (BCAAs) and are often discussed in the same physiological and pathological situations. The two consecutive initial reactions of BCAA catabolism are catalyzed by the common enzymes referred to as branched chain aminotransferase (BCAT) and branched chain α-keto acid dehydrogenase (BCKDH). BCAT transfers the amino group of BCAAs to 2-ketoglutarate, which results in corresponding branched chain 2-keto acids (BCKAs) and glutamate. BCKDH performs an oxidative decarboxylation of BCKAs, which produces their coenzyme A-conjugates and NADH. BCAT2 in skeletal muscle dominantly catalyzes the transamination of BCAAs. Low BCAT activity in the liver reduces the metabolization of BCAAs, but the abundant presence of BCKDH promotes the metabolism of muscle-derived BCKAs, which leads to the production of glucose and ketone bodies. While mutations in the genes responsible for BCAA catabolism are involved in rare inherited disorders, an aberrant regulation of their enzymatic activities is associated with major metabolic disorders such as diabetes, cardiovascular disease, and cancer. Therefore, an understanding of the regulatory process of metabolic enzymes, as well as the functions of the BCAAs and their metabolites, make a significant contribution to our health.

Double-Edge Effects of Leucine on Cancer Cells

Leucine is an essential amino acid that cannot be produced endogenously in the human body and therefore needs to be obtained from dietary sources. Leucine plays a pivotal role in stimulating muscle protein synthesis, along with isoleucine and valine, as the group of branched-chain amino acids, making them one of the most popular dietary supplements for athletes and gym-goers. The individual effects of leucine, however, have not been fully clarified, as most of the studies so far have focused on the grouped effects of branched-chain amino acids. In recent years, leucine and its metabolites have been shown to stimulate muscle protein synthesis mainly via the mammalian target of the rapamycin complex 1 signaling pathway, thereby improving muscle atrophy in cancer cachexia. Interestingly, cancer research suggests that leucine may have either anti-cancer or pro-tumorigenic effects. In the current manuscript, we aim to review leucine's roles in muscle protein synthesis, tumor suppression, and tumor progression, specifically summarizing the molecular mechanisms of leucine's action. The role of leucine is controversial in hepatocellular carcinoma, whereas its pro-tumorigenic effects have been demonstrated in breast and pancreatic cancers. In summary, leucine being used as nutritional supplement for athletes needs more attention, as its pro-oncogenic effects may have been identified by recent studies. Anti-cancer or pro-tumorigenic effects of leucine in various cancers should be further investigated to achieve clear conclusions.

The role of amino acids in skeletal muscle health and sarcopenia: A narrative review

The skeletal muscle is the largest organ present inside the body and is responsible for mechanical activities like maintaining posture, movement, respiratory function, and support for the health and functioning of other systems of the body. Skeletal muscle atrophy is a condition associated with a reduction in muscle size, strength, and activity, which leads to an increased dependency on movement, an increased risk of falls, and a reduced quality of life. Various conditions like osteoarthritis, osteoporosis, and fractures are directly associated with an increased muscle atrophy. Additionally, numerous risk factors, like aging, malnutrition, physical inactivity, and certain disease conditions, through distinct pathways negatively affect skeletal muscle health and lead to muscle atrophy. Among the various determinants of the overall muscle health, the rate of muscle protein synthesis and degradation is an important parameter that eventually alters the fate of overall muscle health. In conditions of excessive skeletal muscle atrophy, including sarcopenia, the rate of muscle protein degradation usually exceeds the rate of protein synthesis. The availability of amino acids in the systemic circulation is a crucial step for muscle protein synthesis. The current review aimed to consolidate the existing evidence of amino acids, highlight their mechanisms of action, and assess their roles and effectiveness in enhancing skeletal muscle health.

Sex-Based Effects of Branched-Chain Amino Acids on Strength Training Performance and Body Composition

BACKGROUND

Branched-chain amino acids (BCAAs) are widely studied for their effects on muscle recovery and performance.

AIMS

This study examined the effects of BCAA supplementation on anthropometric data, physical performance, delayed onset muscle soreness (DOMS), and fatigue in recreational weightlifters.

METHODS

The trial involved 100 participants (50 men and 50 women), randomized into BCAA and placebo groups. Subjects in the BCAA group took five daily capsules of 500 mg L-leucine, 250 mg L-isoleucine, and 250 mg L-valine for six months. A two-way ANOVA was used to analyze the main and interaction effects of sex and treatment.

RESULTS

Notable findings include significant improvements in muscle recovery, as indicated by reduced DOMS, particularly in women who showed a decrement of 18.1 ± 9.4 mm compared to 0.8 ± 1.2 mm in the placebo group of a horizontal 100 mm line. Fatigue perception was also significantly lower in the BCAA group, with women reporting a greater decrease (2.6 ± 1.5 scores) compared to the placebo group (0.6 ± 0.7 scores). Strength gains were prominent, especially in men, with a 10% increase in bench press maximum observed in the BCAA group. The interaction between sex and treatment was significant, suggesting sex-specific responses to BCAA supplementation.

CONCLUSIONS

These results underscore the effectiveness of BCAA supplementation in enhancing muscle recovery, reducing fatigue, and improving strength. This study also highlights sex-specific responses, with women benefiting more in terms of DOMS and fatigue reduction, while men experienced greater strength gains, suggesting a need for tailored supplementation strategies.

Embryonic Leucine Promotes Early Postnatal Growth via mTOR Signalling in Japanese Quails

Nutritional cues during embryonic development can alter developmental trajectories and affect postnatal growth. However, the specific mechanisms by which nutrients influence avian growth remain largely unknown. Amino acids can directly interact with the nutrient-sensing pathways, such as the insulin-like growth factor 1 (IGF-1)/mechanistic target of rapamycin (mTOR) pathways, which are known to regulate growth. We examined the effects of embryonic leucine on gene expression and phenotypic growth in Japanese quails by injecting 2.5 mg leucine or saline (control) into Japanese quail eggs on the tenth day of incubation and incubating them under standard conditions. The treatment groups had similar hatching success and size at hatching. However, between 3 and 7 days post-hatching, quails treated with embryonic leucine showed increased growth in body mass and wing, tarsus, head, and intestinal lengths, lasting up to 21 days. The hepatic expression of IGF1, IGF1R, mTOR, and RPS6K1 was upregulated in leucine-treated quails, while the expression of FOXO1 remained unaffected. In conclusion, a subtle increase in embryonic leucine may induce developmental programming effects in Japanese quail by interacting with the IGF-1/mTOR nutrient-sensing pathway to promote growth. This study highlights the role of embryonic amino acids as crucial nutrients for enhancing growth. It provides valuable insight into nutrient intervention strategies during embryonic development to potentially improve poultry growth performance.

Animal board invited review: Dietary transition from animal to plant-derived foods: Are there risks to health?

Animal-derived foods (ADFs) are a very varied group of foods, but many are nutrient rich and contain higher quality protein than provided by plant-derived foods such that a simple replacement of ADF protein is likely to lead to a reduction in overall protein quality. In addition, many ADFs are richer in some nutrients than plant-based foods (e.g. Fe, Ca) and these often have a higher bioavailability. ADFs also provide nutrients that plants cannot supply (e.g. vitamin B12) and some provide beneficial health functionality (e.g. hypotensive) which is not explained by traditional nutrition. However, there remains a good health reason to increase the proportion of plant-derived food in many diets to increase the intake of dietary fibre which is often consumed at very sub-optimal levels. It seems logical that the increased plant-derived foods should replace the ADFs that have the least benefit, the greatest risk to health and the highest environmental impact. Processed meat fits these characteristics and should be an initial target for replacement with plant-based based protein-rich foods that additionally provide the necessary nutrients and have high-quality dietary fibre. Processed meat covers a wide range of products including several traditional foods (e.g. sausages) which will make decisions on food replacement challenging. There is therefore an urgent need for research to better define the relative health risks associated with the range of processed meat-based foods. The aim of this review is to examine the evidence on the benefits and risks of this dietary transition including the absolute necessity to consider initial nutrient status before the replacement of ADFs is considered.

Peanut hulls, an underutilized nutritious culinary ingredient: valorizing food waste for global food, health, and farm economies-a narrative review

Peanut hulls (PHs) are an edible food waste that is an underutilized food source for human consumption. While edible and palatable, currently they are mainly diverted to livestock feed or building materials. Here, we describe existing literature supporting human food valorization of PHs, and propose methods to optimize recapturing nutrients (protein, fiber, phenols and other phytonutrients) lost by treating PHs as waste. Incorporated into common foods, PHs could be processed into functional ingredients to improve nutrient-density with anticipated corresponding positive health outcomes associated with increases in plant foods. Valorization of PHs addresses multiple priorities of the UN Sustainable Development Goals using a Food Systems Approach (FSA) including reducing food waste, increasing economic opportunities for farmers, and increasing the availability of healthy shelf-stable foodstuffs to address food security. Recent advances in sustainable food processing technologies can be utilized to safely incorporate PHs into human food streams. We propose future applications that could make meaningful impacts for food availability and the nutritional composition of common foods like bread and plant-based meat alternatives. While the limited literature on this topic spans several decades, no commercial operations currently exist to process PHs for human consumption, and most literature on the topic precedes the technological "green revolution." The approaches outlined in this review may help bolster commercialization of this underutilized and nutritious food potentially improving opportunities for multiple global stakeholders.

Myoprotective whole foods, muscle health and sarcopenia in older adults

PURPOSE OF REVIEW

Sarcopenia increases in prevalence at older ages and may be exacerbated by poor diet. Whole foods rich in specific nutrients may be myoprotective and mitigate the risk of sarcopenia. Here we review recent evidence published from observational and intervention studies regarding myoprotective foods and explore their benefit for the prevention and/or treatment of sarcopenia in older adults.

RECENT FINDINGS

We found limited new evidence for the role of whole foods in sarcopenia and sarcopenia components (muscle mass, strength, physical performance). There was some evidence for higher consumption of protein-rich foods (milk and dairy) being beneficial for muscle strength in observational and intervention studies. Higher consumption of antioxidant-rich foods (fruit and vegetables) was associated with better physical performance and lower odds of sarcopenia in observational studies. Evidence for other protein- and antioxidant-rich foods were inconsistent or lacking. There remains a clear need for intervention studies designed to identify the role of whole foods for the treatment of sarcopenia.

SUMMARY

Although evidence for myoprotective roles of dairy, fruit and vegetables is emerging from observational studies, higher level evidence from intervention studies is needed for these foods to be recommended in diets of older adults to prevent and/or treat sarcopenia.

Gold and Silver Nanoparticles as Biosensors: Characterization of Surface and Changes in the Adsorption of Leucine Dipeptide under the Influence of Substituent Changes

Early detection of diseases can increase the chances of successful treatment and survival. Therefore, it is necessary to develop a method for detecting or sensing biomolecules that cause trouble in living organisms. Disease sensors should possess specific properties, such as selectivity, reproducibility, stability, sensitivity, and morphology, for their routine application in medical diagnosis and treatment. This work focuses on biosensors in the form of surface-functionalized gold (AuNPs) and silver nanoparticles (AgNPs) prepared using a less-time-consuming, inexpensive, and efficient synthesis route. This allows for the production of highly pure and stable (non-aggregating without stabilizers) nanoparticles with a well-defined spherical shape, a desired diameter, and a monodisperse distribution in an aqueous environment, as confirmed by transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM-EDS), X-ray diffraction (XRD), photoelectron spectroscopy (XPS), ultraviolet-visible (UV-VIS) spectroscopy, and dynamic light scattering (DLS). Thus, these nanoparticles can be used routinely as biomarker sensors and drug-delivery platforms for precision medicine treatment. The NPs' surface was coated with phosphonate dipeptides of L-leucine (Leu; l-Leu-C(R1)(R2)PO3H2), and their adsorption was monitored using SERS. Reproducible spectra were analyzed to determine the orientation of the dipeptides (coating layers) on the nanoparticles' surface. The appropriate R2 side chain of the dipeptide can be selected to control the arrangement of these dipeptides. This allows for the proper formation of a layer covering the nanoparticles while also simultaneously interacting with the surrounding biological environment, such as cells, tissues, and biological fluids.