Hydrazone Bond Research Articles

Chemical modification of bradykinin-polymer conjugates for optimum delivery of nanomedicines to tumors

We recently prepared pH-responsive HPMA copolymer conjugates of bradykinin (P-BK), which release BK in response to the acidic tumor microenvironment, and found that administration of P-BK increased the tumor accumulation and therapeutic efficacy of nanomedicine. Because the release of BK from P-BK determines its onset of action, P-BKs with different release rates were prepared, and their properties were evaluated. The release kinetics were significantly altered by substitution proximal to hydrazone bond, release constant of methyl-substituted P-BK (P-MeBK) was approximately 4- and 80-fold higher than that of cyclopropyl-substituted P-BK (P-CPBK) and phenyl-substituted P-BK (P-PhBK). None of the P-BKs were active, but the release of BK restored their BK-like activity. Pre-administration of the P-BKs increased the tumor accumulation of nanomedicine in C26 tumor-bearing mice by 2- and 1.4-fold for P-MeBK and P-PhBK at 3 and 6 h. Altogether, this study provides insights into the design of pH-responsive nanodrugs with the desired release properties to target acidic lesions such as cancer and inflammation.

Branched glycopolymer prodrug-derived nanoassembly combined with a STING agonist activates an immuno-supportive status to boost anti-PD-L1 antibody therapy

Despite the great potential of anti-PD-L1 antibodies for immunotherapy, their low response rate due to an immunosuppressive tumor microenvironment has hampered their application. To address this issue, we constructed a cell membrane-coated nanosystem (mB4S) to reverse an immunosuppressive microenvironment to an immuno-supportive one for strengthening the anti-tumor effect. In this system, Epirubicin (EPI) as an immunogenic cell death (ICD) inducer was coupled to a branched glycopolymer via hydrazone bonds and diABZI as a stimulator of interferon genes (STING) agonist was encapsulated into mB4S. After internalization of mB4S, EPI was acidic-responsively released to induce ICD, which was characterized by an increased level of calreticulin (CRT) exposure and enhanced ATP secretion. Meanwhile, diABZI effectively activated the STING pathway. Treatment with mB4S in combination with an anti-PD-L1 antibody elicited potent immune responses by increasing the ratio of matured dendritic cells (DCs) and CD8+ T cells, promoting cytokines secretion, up-regulating M1-like tumor-associated macrophages (TAMs) and down-regulating immunosuppressive myeloid-derived suppressor cells (MDSCs). Therefore, this nanosystem for co-delivery of an ICD inducer and a STING agonist achieved promotion of DCs maturation and CD8+ T cells infiltration, creating an immuno-supportive microenvironment, thus potentiating the therapy effect of the anti-PD-L1 antibody in both 4T1 breast and CT26 colon tumor mice.

Endoperoxide-enhanced self-assembled ROS producer as intracellular prodrugs for tumor chemotherapy and chemodynamic therapy.

Prodrug-based self-assembled nanoparticles (PSNs) with tailored responses to tumor microenvironments show a significant promise for chemodynamic therapy (CDT) by generating highly toxic reactive oxygen species (ROS). However, the insufficient level of intracellular ROS and the limited drug accumulation remain major challenges for further clinical transformation. In this study, the PSNs for the delivery of artesunate (ARS) are demonstrated by designing the pH-responsive ARS-4-hydroxybenzoyl hydrazide (HBZ)-5-amino levulinic acid (ALA) nanoparticles (AHA NPs) with self-supplied ROS for excellent chemotherapy and CDT. The PSNs greatly improved the loading capacity of artesunate and the ROS generation from endoperoxide bridge using the electron withdrawing group attached directly to C10 site of artesunate. The ALA and ARS-HBZ could be released from AHA NPs under the cleavage of hydrazone bonds triggered by the acidic surroundings. Besides, the ALA increased the intracellular level of heme in mitochondria, further promoting the ROS generation and lipid peroxidation with ARS-HBZ for excellent anti-tumor effects. Our study improved the chemotherapy of ARS through the chemical modification, pointing out the potential applications in the clinical fields.

Novel Radiochromic Elastomer Dosimeter Based on the Self-Sensitizing Effect of Disulfide Bonds.

γ-Irradiation is a kind of high-energy ionizing ray, which has widespread applications in material, food, and medical industries as well as in the environment. Since this irradiation is invisible, quantitatively monitoring its exposure doses is crucial to irradiated targets. As a type of dosimeter, radiochromic dosimeters can detect γ-irradiation by color changing, and its strategy to realize the radiochromic behavior basically relies on active radicals from radiolysis of an external environmental medium. However, the primary problem of this external environment-mediated sensitization strategy is that it complicates the components of dosimeters. Herein, we present a novel type of self-sensitizing radiochromic poly(urethane-urea) elastomers (PUUEs), where disulfide bonds, serving as radiation-responsive and sensitizing units, are introduced. This is the first attempt to utilize radicals generated from radiolysis of weak bonds in a solid polymer matrix to sensitize color change of dye-doped radiochromic dosimeters. Moreover, it is intriguing that the simultaneously introduced aryl hydrazone bond endows dosimeters with excellent color retention and maintains the Δa* value of 72.9% even after 1 month on the basis of the as-irradiated specimen. Besides, the metathesis of disulfide bonds not only endows dosimeters with better self-healing capability, but also accelerates the postcuring behavior and hydrogen bond reconfiguration, resulting in improved mechanical performance.

Highly hydrophilic methacrylamide-based copolymers as precursors for polymeric nanomedicines containing anthracyclines

The crucial limitation of most low molecular weight cytostatic drugs, including anthracyclines, is their nonspecific biodistribution causing severe adverse effects during cancer treatment. Recently, nanomedicines such as polymer-based systems have been developed as advanced drug delivery systems. Herein, we report the design, synthesis, and characterization of highly water-soluble polymer-carriers based on N‑(1,3‑dihydroxyprop-2-yl)methacrylamide (DHPMA). Polymers differing in molecular weight, hydrodynamic size, and dispersity were synthesized via free or controlled radical polymerization and conjugated to an anthracycline drug pirarubicin (THP) via a pH-sensitive hydrazone bond achieving up to 21 wt% of THP. The DHPMA copolymers were extensively compared to the well-known drug delivery vectors, N-(2-hydroxypropyl)methacrylamide (HPMA)-based copolymers. Importantly, DHPMA-based conjugates showed excellent hydrophilicity exceeding that of HPMA-based copolymers and did not aggregate even after loading with THP reaching 21 wt%. The DHPMA-based polymer nanomedicines exhibited excellent cytotoxicity, body biodistribution, tumor accumulation, and antitumor efficacy, significantly reducing the side effects and toxicity comparable to HPMA-based systems, thus demonstrating their applicability and suitability as efficient drug carriers.

A hierarchically acidity-unlocking nanoSTING stimulant enables cascaded STING activation for potent innate and adaptive antitumor immunity.

Rationale: Neoadjuvant chemotherapy (NAC) has been recognized as an indispensable strategy for advanced malignancies. Nevertheless, the enhancement of overall patient survival in NAC recipients has encountered challenges due to the limited sustainability of its efficacy and the inability to prevent postoperative tumor recurrence and metastasis. Methods: We devise a hierarchically unlocking nanoSTING stimulant liposome (AUG) as a neoadjuvant chemoimmunotherapy agent in the debulking of tumors prior to surgery and prevention of postoperative tumor recurrence and metastasis by simultaneously activating innate and adaptive antitumor immune responses. In the weakly acidic tumor microenvironment, the hydrazone bond within AUG is initially cleaved, leading to the release of a cyclic seven-membered ring containing tertiary amine that serve to activate the stimulator of interferon genes (STING) pathway. Following this, AUG undergoes degradation within lysosomes, facilitating the release of doxorubicin and ultimately inducing immunogenic cell death along with leakage of double-stranded DNA into the cytoplasm. Results: The hierarchically acidity-unlocking pattern enables cascaded STING activation, achieving over 90% tumor growth inhibition in subcutaneous xenograft model and preventing 75% of mice from postsurgical metastasis or recurrence when combined with immune checkpoint inhibitors. Conclusion: Our strategy highlights the potency of AUG as a neoadjuvant paradigm for presurgical tumor debulking and as a preventive measure against postoperative tumor recurrence and metastasis.

Comparing organic and metallo-organic hydrazone molecular cages as potential carriers for doxorubicin delivery.

Molecular cages are three-dimensional supramolecular structures that completely wrap guest molecules by encapsulation. We describe a rare comparative study between a metallo-organic cage and a fully organic analogous system, obtained by hydrazone bond formation self-assembly. Both cages are able to encapsulate the anticancer drug doxorubicin, with the organic cage forming a 1 : 1 inclusion complex with μM affinity, whereas the metallo-organic host experiences disassembly by interaction with the drug. Stability experiments reveal that the ligands of the metallo-organic cage are displaced in buffer at neutral, acidic, and basic pH, while the organic cage only disassembles under acidic conditions. Notably, the organic cage also shows minimal cell toxicity, even at high doses, whilst the doxorubicin-cage complex shows in vitro anti-cancer activity. Collectively, these results show that the attributes of the pure organic molecular cage are suitable for the future challenges of in vivo drug delivery using molecular cages.

Nano-enabled dynamically responsive living acellular hydrogels.

As a key building block of mammalian tissues, extracellular matrices (ECMs) stiffen under shear deformation and undergo cell-imparted healing after damage, features that regulate cell fate, communication, and survival. The shear-stiffening behavior is attributed to semi-flexible biopolymeric ECM networks. Inspired by the mechanical behavior of ECMs, we develop acellular nanocomposite living hydrogels (LivGels), comprising network-forming biopolymers and anisotropic hairy nanoparticle linkers that mimic the dynamic mechanical properties of living counterparts. We show that a bifunctional dynamic linker nanoparticle (nLinker), bearing semi-flexible aldehyde- and carboxylate-modified cellulose chains attached to rigid cellulose nanocrystals converts bulk hydrogels to ECM-like analogues via ionic and dynamic covalent hydrazone bonds. The nLinker not only enables the manipulation of nonlinear mechanics and stiffness within the biological window, but also imparts self-healing to the LivGels. This work is a step forward in designing living acellular soft materials with complex dynamic properties using bio-based nanotechnology.

Injectable isoniazid-loaded bone cement based on hydrazone bonds achieving long-term release and decent mechanical properties.

A robust and easily manufactured high-strength and long-term release hydrazone-based isoniazid acrylic (HIA) bone cement is reported. The mechanical strength of HIA bone cement is similar to that of normal polymethyl methacrylate (PMMA) bone cement, far surpassing that of traditional isoniazid-containing antibiotic-loaded bone cement (INH bone cement). Isoniazid is connected to the bone cement through bioorthogonal hydrazone chemistry, and it possesses release properties superior to those of INH bone cement, allowing for the sustained release of isoniazid for up to 12 weeks. In vivo and in vitro studies also indicate that HIA cement exhibits better biocompatibility than INH bone cement. The results of this study not only signify progress in the realm of antimicrobial bone cement for addressing bone tuberculosis but also enhance our capacity to create and comprehend high-performing antimicrobial bone cement.

Chemosensitization of tumors via simultaneous delivery of STAT3 inhibitor and doxorubicin through HPMA copolymer-based nanotherapeutics with pH-sensitive activation

We synthesized three novel STAT3 inhibitors (S3iD1-S3iD3) possessing oxoheptanoic residue enabling linkage to HPMA copolymer carrier via a pH-sensitive hydrazone bond. HPMA copolymer conjugates bearing doxorubicin (Dox) and our STAT3 inhibitors were synthesized to evaluate the anticancer effect of Dox and STAT3 inhibitor co-delivery into tumors. S3iD1–3 and their copolymer-bound counterparts (P-S3iD1-P-S3iD3) showed considerable in vitro cytostatic activities in five mouse and human cancer cell lines with IC50 ~0.6–7.9 μM and 0.7–10.9 μM, respectively. S3iD2 and S3iD3 were confirmed to inhibit the STAT3 signaling pathway. The combination of HPMA copolymer-bound Dox (P-Dox) and P-S3iD3 at the dosage showing negligible toxicity demonstrated significant antitumor activity in B16F10 melanoma-bearing mice and completely cured 2 out of 15 mice. P-Dox alone had a significantly lower therapeutic activity with no completely cured mice. Thus, polymer conjugates bearing STAT3 inhibitors may be used for the chemosensitization of chemorefractory tumors.

A Precise and Intelligent Nanomedicine for Salivary Adenoid Cystic Carcinoma Treatment by Combining Antivascular Photodynamic Therapy and Neuroinhibitory Chemotherapy

AbstractSalivary adenoid cystic carcinoma (SACC) is one of the most common salivary gland malignancies. Current clinical therapies have limitations and cannot efficiently prevent the SACC development and metastasis. Hematogenous and neural spread are the two major routes of SACC metastasis. In this study, a precise and intelligent nanomedicine, RCDT, is designed to combine antivascular photodynamic therapy and neuroinhibitory chemotherapy against SACC. A tumor vessel‐targeted and reactive oxygen species (ROS)‐responsive photosensitizer (RC) is synthesized by linking cRGD to chlorin e6 (Ce6) via a bridge between the poly(ethylene glycol) and diselenide bonds. A neural‐targeted and pH‐responsive cytotoxic prodrug (DT) is synthesized by conjugating doxorubicin (DOX) with Tet1, a neural‐targeting peptide, via an acidic‐cleavable hydrazone bond. RC and DT are assembled to form RCDT via hydrophobic interactions, thereby shielding Tet1. Under the guidance of cRGD and the photodynamic action of Ce6, RCDT can precisely disrupt the tumor vasculature and simultaneously disintegrate to expose Tet1 by rupturing the diselenide bond. Guided by Tet1, disintegrated RCDT can be specifically internalized into neurons and release DOX to exert neuroinhibitory effects by cleaving the hydrazone bond. Using these stepwise dual‐targeting and dual‐responsive strategies, RCDT can efficiently suppress the growth and metastasis of SACC.

Pectin based hydrogel with covalent coupled doxorubicin and limonin loading for lung tumor therapy

Self-healing hydrogels have shown great application potential in drug delivery for anti-tumor therapy and tissue engineering. In this research, Doxorubicin (DOX) was coupled onto the oxidized pectin (pec-Ald) to prepare DOX grafted pec-AD and used to fabricate self-healing hydrogel for lung cancer therapy combined with novel herbal medicine extract limonin targeting lung cancer cells. The hydrogel was prepared with P(NIPAM195-co-AH54) cross-linking and the hydrazone bond cross-linked hydrogel showed good mechanical property and self-healing behavior. With pectin composition, the hydrogel was still biodegradable catalyzed by enzyme and in vivo. The hydrogel formed fast fit for injectable application and the hydrogel itself showed moderate lung cancer inhibition activity. With limonin loading, the hydrogel showed synergistic lung cancer therapy with the tumor growth greatly inhibited. The covalent coupling of DOX and loaded limonin in the hydrogel decreased in vivo toxicity and the hydrogel degraded on time. With biodegradability and improved lung cancer therapy efficiency, this DOX grafted self-healing hydrogel could find great potential application in cancer therapy in near future.

Dynamic covalent hydrogel fabricated in porous media through dynamic acylhydrazone bond from reactive precursors for deep profile control

In this work, we proposed a novel hydrogel system for in-depth conformance control through the dynamic covalent bond. Diffluent ketone-bearing and acyl hydrazide-bearing reactive precursors with low molecular weight are injected into the formation simultaneously, then gels in situ through dynamic hydrazone bonds to divert the post-injected fluid to un-swept oil zones. Ketone-bearing and acyl hydrazide-bearing reactive precursors with different reactive group ratios were synthesized by simple radical polymerization and hydrazinolysis. Rheological measurement results proved the two reactive precursors formed dynamic covalent hydrogel (DCG) through dynamic hydrazone bonds in deionized water and mineralized water. The viscoelasticity, flow behavior, and profile control behavior in the porous media of the DCG were evaluated. When the flow behavior and profile control experiments were conducted with a 9 m core, the injection pressure of DCG-20 % of which the molar ratio of the reactive group was 20 % was low (0–0.22 MPa) throughout the injection process, and the resistance factor was 4.40. After fully gelation, the post-water injection pressure significantly increased (0.22–7.54 MPa). The residual resistance factor was 150.80, and the plugging efficiency was 99.34 %. This work proved that the DCG consisting of ketone-bearing and acyl hydrazide-bearing reactive precursors not only had a strong injection capacity but also had a good profile control effect in porous media which meant the DCG fully met the need for deep profile control.

An infection-microenvironment-targeted and responsive peptide-drug nanosystem for sepsis emergency by suppressing infection and inflammation

Sepsis is a life-threatening emergency that causes millions of deaths every year due to severe infection and inflammation. Nevertheless, current therapeutic regimens are inadequate to promptly address the vast diversity of potential pathogens. Omiganan, an antimicrobial peptide, has shown promise for neutralizing endotoxins and eliminating diverse pathogens. However, its clinical application is hindered by safety and stability concerns. Herein, we present a nanoscale drug delivery system (Omi-hyd-Dex@HA NPs) that selectively targets infectious microenvironments (IMEs) and responds to specific stimuli for efficient intervention in sepsis. The system consists of omiganan-dexamethasone conjugates linked by hydrazone bonds which self-assemble into nanoparticles coated with a hyaluronic acid (HA). The HA coating not only facilitates IMEs-targeting through interaction with intercellular-adhesion-molecule-1 on inflamed endotheliocytes, but also improves the biosafety of the nanosystem and enhances drug accumulation in primary infection sites triggered by hyaluronidase. The nanoparticles release dual drugs in IMEs through pH-sensitive cleavage of hydrazone bonds to eradicate pathogens and suppress inflammation. In multiple tissue infection and sepsis animal models, Omi-hyd-Dex@HA NPs exhibited rapid source control and comprehensive inflammation reduction, thereby preventing subsequent fatal complications and significantly improving survival outcomes. The bio-responsive and self-delivering nanosystem offers a promising strategy for systemic sepsis treatment in emergencies.

Adaptable polymerization platform for therapeutics with tunable biodegradability.

Biodegradable polymer-based therapeutics have recently become essential drug delivery biomaterials for various bioactive compounds. Biodegradable and biocompatible polymer-based biomaterials fulfill the requirements of these therapeutics because they enable to obtain polymer biomaterials with optimized blood circulation, pharmacokinetics, biodegradability, and renal excretion. Herein, we describe an adaptable polymerization platform employed for the synthesis of long-circulating, stimulus-sensitive and biodegradable biomaterials, therapeutics, or theranostics. Four chain transfer agents (CTA) were designed and successfully synthesized for the reversible addition-fragmentation chain transfer polymerization, allowing the straightforward synthesis of hydrolytically biodegradable structures of block copolymers-based biomaterials. The controlled polymerization using the CTAs enables controlling the half-life of the hydrolytic degradation of polymer precursors in a wide range from 5h to 21 days. Moreover, the antitumor drug pirarubicin (THP) was successfully conjugated to the polymer biomaterials via a pH-sensitive hydrazone bond for in vitro and in vivo experiments. Polymer conjugates demonstrated superior antitumor efficacy compared to basic linear polymer-based conjugates. Notably, the biodegradable systems, even though those with degradation in the order of hours were selected, increased the half-life of THP in the bloodstream almost two-fold. Indeed, the presented platform design enables the main chain-end specific attachment of targeting ligands or diagnostic molecules. The adaptable polymerization platform design allows tuning of the biodegradability rate, stimuli-sensitive drug bonding, and optimized pharmacokinetics to increase the therapy outcome and system targeting, thus allowing the preparation of targeted or theranostic polymer conjugates. STATEMENT OF SIGNIFICANCE: Biodegradable and biocompatible polymer-based biomaterials are recognized as potential future bioactive nanomedicines. To advance the development of such biomaterials, we developed polymerization platforms utilizing tailored chain transfer agents allowing the straightforward synthesis of hydrolytically degradable polymer biomaterials with tuned biodegradability from hours to several days. The platform allows for the synthesis of long-circulating, stimulus-sensitive and biodegradable biomaterial serving as drug carriers or theranostics. The therapeutic potential was validated by preparation of polymer biomaterials containing pirarubicin, anticancer drug, bound via pH sensitive bond and by showing prolonged blood circulation and increased antitumor activity while keeping the drug side effects low. This work paves the way for future development of biodegradable polymer biomaterials with advanced properties in drug delivery.

Effect of various aryl substitutions on the interfacial interaction energy of graphene/conductive polymer nanocomposites

Studying intermolecular interactions in polymer nanocomposites is highly effective in achieving high-efficiency nanocomposites. To investigate the polymer nanocomposites including conductive polymers, namely poly (3-phenylhydrazone thiophene) (PPHT), poly (3-(4-n-octyl)-phenylthiophene) (POPT), and functionalized graphene nanosheet (FGN), reactive molecular dynamics (RMD) simulation were employed. The FGN structures were a result of the arylation of graphene nanosheets containing different substitutions including sulfide, amine, di-amine, and thiol functional groups. According to interaction energies at polymers / arylated graphene nanosheet, the most interaction energies resulted in nanocomposites of PPHT/graphene-thiophenyl amine (G-PATP) and POPT/graphene-p-Phenylenediamine (G-PPD). Due to the polarity of PPHT, the formation of hydrogen bonding (H-bonding) was expected at specific sites, which were confirmed based on H-bonding interaction criteria. In reality, the criteria required for detecting H-bonding through RDF and the relevant angle measurement have been established. On the other hand, due to the acidic-sensitive hydrazone bond in PPHT, it was expected that the increasing trend in interaction energy of nanocomposites of PPHT could be solely justified based on the acidity of the functional groups employed. However, based on the obtained results, other factors such as the topological polar surface area (TPSA) and the formation of unconventional H-bonding, in addition to the acidity of functional groups, have been considered as influential factors in the changing of interaction energy. Also, the dynamic behavior of polymers was examined by plotting the radius of the gyration (Rg) parameter via time and functional groups. Finally, the temperature effect on interaction energy was determined, too.

Robust covalent organic frameworks membranes for ultrafast dye/salt separation in harsh environments

Although covalent organic frameworks (COFs) membranes have promising applications in water treatment due to their ordered structure and adjustable pore size, most of them are imine-linked ones, which severely limits their application in harsh environments. Herein, we offer a stable novel COFs membrane which is composed of hydrazone bonds and β-ketoenamine structures. Such β-ketoenamine based COFs composite membrane was fabricated via interfacial catalytic polymerization on a nylon substrate, which was generated at the water (P-Toluenesulfonic acid)/n-hexane (2,5-dimethoxyterephthalhydrazide, 1,3,5-triformylphoroglucinol) interface. The resultant COFs membrane demonstrates excellent chemical stability in strong acidic (2 mol/L)/alkaline (9 mol/L)/organic solvents (dioxane, acetone, methanol, and ethanol) media. The optimized COFs membrane achieved 109.73 L m−2 h−1 bar−1 permeance in Congo Red aqueous solution and 99.56 % CR rejection. This study exploits a novel approach to produce robust COFs membranes under extreme conditions.

An Injectable, Adhesive, and Self-Healing Hydrogel with Inherently Antibacterial Property for Wound Dressing.

Antibacterial hydrogel has emerged as an excellent candidate for wound dressing with the ability to eliminate infection and promote wound healing. Herein, a dynamic hydrogel is developed by Schiff base reaction of mixed charged polypeptides and oxidized dextran (ODex). Specifically, biodegradable polypeptides of 1-(propylthio)acetic acid-3-butylimidazole-modified poly(L-lysine) (PLL-PBIM) and adipate dihydrazide-modified poly(L-glutamic acid) (PLG-ADH) are achieved with tunable substitution and charge. By mixing with ODex, charged polypeptides of PLL-PBIM and PLG-ADH led to an injectable and self-healing hydrogel in seconds. The injectable and self-healing performances of the hydrogels are ascribed to the reversible imine and hydrazone bonds formed between polypeptides and ODex. The positively charged hydrogels exhibited over 95% antibacterial activity against E. coli and S. aureus. An optimized balancing of PLG-ADH and PLL-PBIM significantly reduced the hemolysis rate and cytotoxicity of hydrogels. Therefore, the dynamic hydrogel with excellent biocompatibility and inherently antibacterial ability can have potential application for wound dressing.

Interpenetrating Networks of Collagen and Hyaluronic Acid That Serve as In Vitro Tissue Models for Assessing Macromolecular Transport.

High-fidelity preclinical in vitro tissue models can reduce the failure rate of drugs entering clinical trials. Collagen and hyaluronic acid (HA) are major components of the extracellular matrix of many native tissues and affect therapeutic macromolecule diffusion and recovery through tissues. Although collagen and HA are commonly used in tissue engineering, the physical and mechanical properties of these materials are variable and depend highly on processing conditions. In this study, HA was chemically modified and crosslinked via hydrazone bonds to form interpenetrating networks of crosslinked HA (HAX) with collagen (Col). These networks enabled a wide range of mechanical properties, including stiffness and swellability, and microstructures, such as pore morphology and size, that can better recapitulate diverse tissues. We utilized these interpenetrating ColHAX hydrogels as in vitro tissue models to examine macromolecular transport and recovery for early-stage drug screening. Hydrogel formulations with varying collagen and HAX concentrations imparted different gel properties based on the ratio of collagen to HAX. These gels were stable and swelled up to 170% of their original mass, and the storage moduli of the ColHAX gels increased over an order of magnitude by increasing collagen and HA concentration. Interestingly, when HAX concentration was constant and collagen concentration increased, both the pore size and spatial colocalization of collagen and HA increased. HA in the system dominated the ζ-potentials of the gels. The hydrogel and macromolecule properties impacted the mass transport and recovery of lysozyme, β-lactoglobulin, and bovine serum albumin (BSA) from the ColHAX gels─large molecules were largely impacted by mesh size, whereas small molecules were influenced primarily by electrostatic forces. Overall, the tunable properties demonstrated by the ColHAX hydrogels can be used to mimic different tissues for early-stage assays to understand drug transport and its relationship to matrix properties.

Coaxial extrusion bioprinting of hydrazone crosslinked POEGMA hydrogels: Optimizing needle geometry to achieve improved print quality

Facilitating effective mixing of two or more functional polymers remains a challenge when translating in situ-crosslinking click chemistry hydrogels to extrusion bioprinting applications. In this work, the conventional flush coaxial needle was modified to introduce a mixing region to promote the mixing of low-viscosity hydrazide and aldehyde-functionalized poly (oligoethylene glycol methacrylate) (POEGMA) polymers that form dynamic hydrazone bonds upon crosslinking. The inclusion of the mixing region significantly reduced the spreading of the printed fibers and improved the homogeneity of both the printed hydrogel and the encapsulated cells. Computational modeling based on non-Newtonian fluid behavior in the mixing zone confirmed that increasing the length of the mixing zone improved the mixing efficiency, a finding supported by experimental printing results. As such, particularly with less viscous bioinks like the oligomeric hydrazide/aldehyde-functionalized POEGMA polymers used herein, the inclusion of this mixing region provides an effective means of printing functional precursor polymers that can chemically crosslink upon mixing.