Ehsan Mohammadifar

Primary mixed glial cultures are key tools to isolate and study astrocytes, microglia and oligodendrocytes. Cell-substrate adhesion is critical for neural cell survival and differentiation. Cationic polymers like poly-D-lysine (PDL) are widely used to promote cell adhesion to cell culture substrates, however, PDL is not stable long-term, with cultured cells often detaching (peeling) after 2-3 weeks. Dendritic polyglycerol amine (dPGA) is a synthetic polycationic non-protein polymer biomimetic of poly-lysine that is highly resistant to degradation by cellular proteases. Substrates coated with dPGA promote cell adhesion and improve survival in long-term neuronal cultures. Here we assessed dPGA as a substrate coating to provide long-term support for mixed glial cultures. Oligodendrocyte precursor cells (OPCs) were isolated weekly by differential adhesion from cultures grown in T75 flasks with PDL or dPGA-coated substrates. Following two “shake-off” isolations, the cell layer in most PDL-coated flasks fully detached, rendering these flasks unusable for further culture. In contrast, dPGA-coated flasks consistently yielded cells for six or more sequential isolations over seven weeks in culture. dPGA-coated flasks produced more cells, a greater percentage of O4+ cells, and maintained similar proportions of OPCs and MBP-positive cells as when isolated from a PDL-coated substrate. dPGA is cyto-compatible, functionally superior, easy to use, low cost and a stable alternative to conventional cell substrate coatings. The enhanced long-term stability of mixed glial cultures grown on a dPGA substrate has the capacity to increase cellular yield, reduce animal use, and facilitate studies of oligodendrocyte cell biology.

In Nature, most known objects can perform their functions only when in supramolecular self‐assembled from, e.g. protein complexes and cell membranes. Here, a dendritic polymer is presented that inhibits severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) with an irreversible (virucidal) mechanism only when self‐assembled into a Two‐dimmensional supramolecular polymer (2D‐SupraPol). Monomeric analogs of the dendritic polymer can only inhibit SARS‐CoV‐2 reversibly, thus allowing for the virus to regain infectivity after dilution. Upon assembly, 2D‐SupraPol shows a remarkable half‐inhibitory concentration (IC₅₀ 30 nM) in vitro and in vivo in a Syrian Hamster model has a good efficacy. Using cryo‐TEM, it is shown that the 2D‐SupraPol has a controllable lateral size that can be tuned by adjusting the pH and use small angle X‐ray and neutron scattering to unveil the architecture of the supramolecular assembly. This functional 2D‐SupraPol, and its supramolecular architecture are proposed, as a prophylaxis nasal spray to inhibit the virus interaction with the respiratory tract.

Infectious wounds occur when harmful microorganisms such as bacteria or viruses invade a wound site. Its problems associated include delayed healing, increased pain, swelling, and the potential for systemic infections. Therefore, developing new wound dressing materials with antibacterial effects is crucial for improving the healing process. Here a redox‐degradable hydrogel loaded with an antibacterial peptide (vancomycin) in a straightforward gram‐scale synthesis, is developed. The hydrogel structure consists of a disulfide bond‐containing hyperbranched polyglycerol (SS‐hPG) that is cross‐linked by 4‐arm polyethylene glycol‐thiol (4‐arm PEG‐SH). The polymerization mechanism and full characterization of SS‐hPG are described as this synthesis is reported for the first time. Rheology is used to ascertain the hydrogel's mechanical characteristics, such as stiffness, and self‐healing, determining these properties for different ratios and concentrations of both gel components. The incorporation of disulfide bonds in the hydrogel is proved by conducting degradation experiments in reductive environments. Fluorescein isothiocyanate‐albumin (FITC‐BSA) and vancomycin both are loaded into the gel, and the guest release kinetics is assessed for both slow and on‐demand releases. Finally, the in vitro and in vivo experiments prove that the vancomycin‐loaded hydrogel acts as an antibacterial barrier for wound dressing and accelerates the healing of infectious wounds in a mouse model.

Infectious wounds occur when harmful microorganisms such as bacteria or viruses invade a wound site. Its problems associated include delayed healing, increased pain, swelling, and the potential for systemic infections. Therefore, developing new wound dressing materials with antibacterial effects is crucial for improving the healing process. Here we developed a redox-degradable hydrogel loaded with an antibacterial peptide (vancomycin) in a straightforward gram-scale synthesis. The hydrogel structure consists of a disulfide bond-containing hyperbranched polyglycerol (SS-hPG) which is cross-linked by 4-arm polyethylene glycol-thiol (4-arm PEG-SH). The polymerization mechanism and full characterization of SS-hPG are described as we report this synthesis for the first time. The controlled release of antibacterial peptide follows, as the hydrogel degrades in a reductive environment triggered by glutathione. We used rheology to ascertain the hydrogel’s mechanical characteristics, such as stiffness, and self-healing, determining these properties for different ratios and concentrations of both blocks. Fluorescein isothiocyanate-albumin (FITC-albumin) and vancomycin were both loaded into the gel, and the guest release kinetics were assessed for both slow and ondemand releases. Finally, our in-vitro and in-vivo experiments proved that the vancomycin-loaded hydrogel acts as an antibacterial barrier for wound dressing and accelerates the healing of infectious wounds in a mouse model.

Inflammatory skin diseases, such as psoriasis, atopic dermatitis, and alopecia areata, occur when the regulatory tolerance of the innate immune system is disrupted, resulting in the activation of the Janus kinase-signal transducer and activator of transcription (JAK-STAT) inflammatory signaling pathway by interleukin 6 (IL-6) and other key inflammatory cytokines. JAK inhibitors, such as tofacitinib, bind to these enzymes which are coupled to receptors on cell surfaces and block the transcription of inflammatory cytokine-induced genes. The first topical applications are being marketed, yet insufficient effects regarding indications, such as alopecia areata, suggest that improved delivery technologies could help increase the efficacy. In this study, we used sulfated dendritic polyglycerol with caprolactone segments integrated in its backbone (dPGS-PCL), with a molecular weight of 54 kDa, as a degradable carrier to load and solubilize the hydrophobic drug tofacitinib (TFB). TFB loaded in dPGS-PCL (dPGS-PCL@TFB), at a 11 w/w% loading capacity in aqueous solution, showed in an ex-vivo human skin model better penetration than free TFB in a 30:70 (v/v) ethanol/water mixture. We also investigated the anti-inflammatory efficacy of dPGS-PCL@TFB (0.5 w/w%), dPGS-PCL, and free TFB in the water/ethanol mixture by measuring their effects on IL-6 and IL-8 release, and STAT3 and STAT5 activation in ex vivo skin models of simulated inflamed human skin. Our results suggest that dPGS-PCL@TFB reduces the activation of STAT3 and STAT5 by increasing the penetration of the tofacitinib. However, no statistically significant differences with respect to the inhibition of IL-6 and IL-8 were observed in this short incubation time.

The application of micelles as drug delivery systems has gained a great deal of attention as a means to overcome the current several drawbacks present in conventional cancer treatments. In this work, we highlight the comparison of polymeric and monomeric amphiphilic systems with a similar hydrophilic–lipophilic balance (HLB) in terms of their biocompatibility, aggregation behavior in aqueous solution, and potential in solubilizing hydrophobic compounds. The polymeric system consists of non-ionic polymeric amphiphiles synthesized via sequential RAFT polymerization of polyglycerol first-generation [G1] dendron methacrylate and cholesterol methacrylate to obtain poly(G1-polyglycerol dendron methacrylate)-block-poly(cholesterol methacrylate) (pG1MA-b-pCMA). The monomeric system is a polyglycerol second-generation [G2] dendron end-capped to a cholesterol unit. Both amphiphiles form spherical micellar aggregations in aqueous solution, with differences in size and the morphology in which hydrophobic molecules can be encapsulated. The polymeric and monomeric micelles showed a low critical micelle concentration (CMC) of 0.2 and 17 μg/mL, respectively. The results of our cytotoxicity assays showed that the polymeric system has significantly higher cell viability compared to that of the monomeric amphiphiles. The polymeric micelles were implemented as drug delivery systems by encapsulation of the hydrophobic small molecule doxorubicin, achieving a loading capacity of 4%. In summary, the results of this study reveal that using cholesterol as a building block for polymer synthesis is a promising method of preparation for efficient drug delivery systems while improving the cell viability of monomeric cholesterol.

Poor water solubility and low bioavailability of active pharmaceutical ingredients (APIs) are major causes of friction in the pharmaceutical industry and represent a formidable hurdle for pharmaceutical drug development. Drug delivery remains the major challenge for the application of new small‐molecule drugs as well as biopharmaceuticals. The three challenges for synthetic delivery systems are: (i) controlling drug distribution and clearance in the blood; (ii) solubilizing poorly water‐soluble agents, and (iii) selectively targeting specific tissues. Although several polymer‐based systems have addressed the first two demands and have been translated into clinical practice, no targeted synthetic drug delivery system has reached the market. This Review is designed to provide a background on the challenges and requirements for the design and translation of new polymer‐based delivery systems. This report will focus on chemical approaches to drug delivery for systemic applications.

Schlechte Wasserlöslichkeit und geringe Bioverfügbarkeit von pharmazeutischen Wirkstoffen (APIs) sind die Hauptursache für Verzögerungen in der pharmazeutischen Industrie und stellen eine große Hürde für die Entwicklung neuer Arzneimittel dar. Der Transport von Arzneimitteln ist nach wie vor die größte Herausforderung für die Anwendung niedermolekularer Medikamente und Biopharmazeutika. Die drei Herausforderungen für synthetische Transportsysteme sind: (i) Kontrolle über die Wirkstoffverteilung und Clearance im Blut, (ii) Solubilisierung schlecht wasserlöslicher Wirkstoffe und (iii) selektive Akkumulation in bestimmten Geweben. Obwohl viele Polymer‐basierte Systeme die ersten beiden Anforderungen erfüllen und in die klinische Praxis umgesetzt wurden, hat bisher noch kein zielgerichtetes, synthetisches Abgabesystem den Markt erreicht. Dieser Aufsatz soll einen Überblick über die Herausforderungen und Anforderungen zur Entwicklung und Umsetzung neuer Polymer‐basierter Darreichungssysteme geben. Hauptaugenmerk liegt hierbei auf den chemischen Ansätzen für die Darreichung von Wirkstoffen für systemische Anwendungen.

Heparin has been known to be a broad-spectrum inhibitor of viral infection for almost 70 years, and it has been used as a medication for almost 90 years due to its anticoagulant effect. This nontoxic biocompatible polymer efficiently binds to many types of viruses and prevents their attachment to cell membranes. However, the anticoagulant properties are limiting their use as an antiviral drug. Many heparin-like compounds have been developed throughout the years; however, the reversible nature of the virus inhibition mechanism has prevented their translation to the clinics. In vivo, such a mechanism requires the unrealistic maintenance of the concentration above the binding constant. Recently, we have shown that the addition of long hydrophobic linkers to heparin-like compounds renders the interaction irreversible while maintaining the low-toxicity and broad-spectrum activity. To date, such hydrophobic linkers have been used to create heparin-like gold nanoparticles and β-cyclodextrins. The former achieves a nanomolar inhibition concentration on a non-biodegradable scaffold. The latter, on a fully biodegradable scaffold, shows only a micromolar inhibition concentration. Here, we report that the addition of hydrophobic linkers to a new type of multifunctional scaffold (dendritic polyglycerol, dPG) creates biocompatible compounds endowed with nanomolar activity. Furthermore, we present an in-depth analysis of the molecular design rules needed to achieve irreversible virus inhibition. The most active compound (dPG-5) showed nanomolar activity against herpes simplex virus 2 (HSV-2) and respiratory syncytial virus (RSV), giving a proof-of-principle for broad-spectrum while keeping low-toxicity. In addition, we demonstrate that the virucidal activity leads to the release of viral DNA upon the interaction between the virus and our polyanionic dendritic polymers. We believe that this paper will be a stepping stone toward the design of a new class of irreversible nontoxic broad-spectrum antivirals.