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Chemically cross‐linked hydrogels are synthesized from a set of protected L‐lysine and L‐glutamic acid containing homo and copolypetides. Cross‐linking of the linear copolypeptides is achieved through the incorporation of L‐tryptophan and its reaction with hexamethylene bis(triazolinodione). Upon deprotection, hydrogels with oppositely charged polypeptides of different L‐lysine and L‐glutamic acid composition form pH‐dependent polyion complexes through electrostatic interaction. The obtained networks show distinct pH‐dependent differences in their water swelling and rheological properties. Hydrogels at pH 4 display higher strengths compared to pH 8 and their rheological properties scale with L‐lysine/L‐glutamic acid ratio. At pH 8 results suggests that ionic interactions and presumably secondary structure effects have a significant impact on the hydrogel properties. This is further evident from the influence of the copolypetide structures, random versus block copolypeptides, used in the cross‐linked hydrogel. None of the hydrogel shows any significant cytotoxicity against skin cell lines. [ABSTRACT FROM AUTHOR]

1. Although valuable in vitro models exist to study drug elimination from the systemic circulation, more integrated models may improve mechanistic insight in a biorelevant setting. 2. This study aimed to explore (1) intestinal and biliary excretion of the HIV protease inhibitor darunavir and its impact on systemic disposition and (2) to evaluate to what extent findings in an in situ excretion model in rat can be captured by individual in vitro models. 3. Contemporary in vitro models were applied to study intestinal and hepatobiliary disposition of darunavir and data were compared with findings in the in situ excretion model. 4. Both in situ and in vitro experiments demonstrated significant metabolism of darunavir, which could be strongly inhibited by the P450 inhibitor 1-aminobenzotriazole. Using the P-gp inhibitor zosuquidar, P-gp mediated excretion of darunavir from blood towards gastrointestinal lumen was evidenced and this was confirmed by transport studies in Caco-2 cells. Moreover, involvement of P-gp in the biliary excretion of darunavir was also demonstrated in situ. 5. In general, in situ findings corresponded well with in vitro data. The in situ excretion model offers the possibility to gain mechanistic insight in intestinal and hepatobiliary excretion processes and, at the same time, evaluate their impact on the systemic disposition of a compound. [ABSTRACT FROM AUTHOR]

Stromal-Derived Factor 1α (SDF) is an angiogenic, chemotactic protein with significant potential for applications in a range of clinical areas, including wound healing, myocardial infarction and orthopaedic regenerative approaches. The 26-min in vivo half-life of SDF, however, has limited its clinical translation to date. In this study, we investigate the use of star-shaped or linear poly(glutamic acid) (PGA) polypeptides to produce PGA–SDF nanoparticles, which can be incorporated into a tyramine-modified hyaluronic acid hydrogel (HA–TA) to facilitate sustained localised delivery of SDF. The physicochemical properties and biocompatibility of the PGA–SDF nanoparticle formulations were extensively characterised prior to incorporation into a HA–TA hydrogel. The biological activity of the SDF released from the nano-in-gel system was determined on Matrigel®, scratch and Transwell® migration assays. Both star-shaped and linear PGA facilitated SDF nanoparticle formation with particle sizes from 255–305 nm and almost complete SDF complexation. Star-PGA–SDF demonstrated superior biocompatibility and was incorporated into a HA–TA gel, which facilitated sustained SDF release for up to 35 days in vitro. Released SDF significantly improved gap closure on a scratch assay, produced a 2.8-fold increase in HUVEC Transwell® migration and a 1.5-fold increase in total tubule length on a Matrigel® assay at 12 h compared to untreated cells. Overall, we present a novel platform system for the sustained delivery of bioactive SDF from a nano-in-gel system which could be adapted for a range of biomedical applications. [ABSTRACT FROM AUTHOR]

The organic cation transporter-1 (OCT1) mediates hepatic uptake of cationic endogenous compounds and xenobiotics. To date, limited information exists on how Oct1/OCT1 functionally develops with age in rat and human livers) and how this would affect pharmacokinetics of OCT substrates in children or juvenile animals. The functional ontogeny of rOct/hOCT was profiled in suspended rat (2-57 days old) and human hepatocytes (paediatric liver tissue donors: age 2-12 months) by determining uptake clearance of 4-[4-(dimethylamino)styryl]-N-methylpyridinium iodide (ASP + ) as a known rOct/hOCT probe substrate. mRNA expression was determined in rat liver tissue corresponding to rat ages used in the functional studies, while hOCT1 mRNA expressions were determined in the same hepatocyte batches as used for uptake studies. Maturation of rOct/hOCT activity and expression were evaluated by comparing values obtained at the various ages to the adult values. Relative to adult values (at 8 weeks), ASP + uptake clearance in suspended rat hepatocytes aged 0, 1, 2, 3, 4, 5 and 6 weeks reached 26, 29, 33, 37, 72, 63 and 71%, respectively. Hepatic Oct1 mRNA expression was consistent with Oct activity (correlation coefficient of 0.92). In human hepatocytes, OCT1 activity was age-dependent and also correlated with mRNA levels (correlation coefficient of 0.88). These data show thatOct1/OCT1 activities and expression mature gradually in rat/human liver, thereby mirroring the expression pattern of Organic Anion Transporting Polypeptide (Oatp1b2) in rat. These high-resolution transporter ontogeny profiles will allow for more accurate prediction of the pharmacokinetics of OCT1/Oct1 substrates in paediatric populations and juvenile animals. Significance Statement Organic Cation Transporter-1 (OCT1) represents a major drug uptake transporter in human liver. This study provides high resolution data regarding the age-dependent function of OCT1 in the liver, based on in vitro experiments with rat and human hepatocytes obtained from donors between birth and adulthood. These ontogeny profiles will inform improved age-specific physiologically-based pharmacokinetic (PBPK) models for OCT1 drug substrates in neonates, infants, children and adults., (Copyright © 2024 American Society for Pharmacology and Experimental Therapeutics.)

Introduction: The sandwich-cultured hepatocyte (SCH) model has become an invaluable in vitro tool for studying hepatic drug transport, metabolism, biliary excretion and toxicity. The relevant expression of many hepatocyte-specific functions together with the in vivo-like morphology favor SCHs over other preclinical models for evaluating hepatobiliary drug disposition and drug-induced hepatotoxicity., Areas Covered: In this review, the authors highlight recommended procedures required for reproducibly culturing hepatocytes in sandwich configuration. It also provides an overview of the SCH model characteristics as a function of culture time. Lastly, the article presents a summary of the most prominent applications of the SCH model, including hepatic drug clearance prediction, drug-drug interaction potential and drug-induced hepatotoxicity., Expert Opinion: When human (cryopreserved) hepatocytes are used to establish sandwich cultures, the model appears particularly valuable to quantitatively investigate clinically relevant mechanisms related to in vivo hepatobiliary drug disposition and hepatotoxicity. Nonetheless, the SCH model would largely benefit from better insight into the fundamental cell signaling mechanisms that are critical for long-term in vitro maintenance of the hepatocytic phenotype. Studies systematically exploring improved cell culture conditions (e.g., co-cultures or extracellular matrix modifications), as well as in vitro work identifying key transcription factors involved in hepatocyte differentiation are currently emerging.