Injectable Liposome-based Supramolecular Hydrogels for the Programmable Release of Multiple Protein Drugs

Orally-deliverable liposome-microgel complexes dynamically remodel intestinal environment to enhance probiotic ulcerative colitis therapy via TLR4 inhibition and tryptophan metabolic crosstalk

Probiotics emerges as a promising option for ulcerative colitis (UC) treatment, but its application remains challenging due to insufficient colon-targeted delivery efficiency and survival against the inflammation-associated intestinal oxidative stress. To address these issues, here we report a supramolecular liposome-microgel complex (SLMC) incorporated with Bacillus subtilis spores (BSSs) and dexamethasone (DEX) for orally-deliverable probiotic UC therapy. Specifically, BSSs and cholesterols were conjugated with gelatin via diselenide ligation to prepare microgels, followed by supramolecular complexation with UC-targeted DEX-loaded liposome via microfluidic engineering. The orally-administered SLMC efficiently accumulated in UC-affected colonic sites to release BSSs and DEX. DEX elicited rapid anti-inflammatory effect to reduce ROS generation, which cooperated with the ROS consumption by spore germination and diselenide cleavage to orchestrate an anaerobic intestinal microenvironment, thus promoting Bacillus subtilis colonization to restore gut homeostasis and initiate anti-inflammatory microbiota-macrophage metabolic crosstalk. Indeed, in vivo analysis showed that the SLMC treatment markedly inhibited pro-inflammatory TLR4-NF-κB signaling activities in mucosal macrophages through localized DEX delivery and boosting tryptophan metabolite production, leading to robust and durable UC abolishment. This study offers a practical approach for improving UC treatment in the clinic.

Mechanoregulative hydrogel facilitates rapid scarless healing by self-adaptive control of wound niche at different stages

It is essential to spatiotemporally control the microniche of wound at different healing stages for rapid and scarless healing. Hence, a multifunctional soft hydrogel integrated with programmed drug release capability (MLVgel) was fabricated. MLVgel is adhesive and moldable with low friction response, which provides moisture and responses to an infectious environment to deliver bactericidal and antioxidant effects in rat bacterial infection and burn wound models. By release control, instant short-term inflammation suppression is combined with sustained mechano-transduction signal inhibition. This dynamically modulates immune responses and delays En1+ fibroblast activation via the YAP-TEAD pathway, ultimately facilitating scarless wound regeneration. Genomic analyses showed that the enhanced reepithelization and mechanoregulation by MLVgel during different wound phases are indispensable for its therapeutic outcomes. Last, MLVgel resulted in markedly improved healing in a pig mature scar model, which demonstrated its translation potential. Our results also verified the necessity of programed dynamic regulation in the healing process.

Preparation, characterization, multidimensional applications and prospects of protein bio-based hydrogels: A review

Protein bio-based hydrogels have emerged as a versatile and functional class of biomaterials due to their unique properties, including biocompatibility, biodegradability, tunable mechanical strength, and environmental responsiveness (pH, enzymes, ions and light). This review comprehensively explores the preparation methods, physicochemical properties, and multidimensional applications of protein-based hydrogels. Various fabrication techniques, such as chemical crosslinking, physical gelation, and enzymatic reactions, are discussed, highlighting their impact on the structure and functionality of hydrogels. The intrinsic properties of protein hydrogels are summarized in detail, including mechanical properties, swelling resistance, frost resistance, adhesion, biocompatibility and degradability. Furthermore, this review delves into their diverse applications, which span tissue engineering, drug delivery, wound healing, food preservation, biosensing, and environmental remediation. Finally, the challenges and future prospects of protein-based hydrogels are addressed, emphasizing the necessity for scalable production, enhanced stability, and multifunctional integration to meet the growing demands of advanced biomedical and industrial applications. This review aims to provide a comprehensive understanding of protein-based hydrogels and to inspire innovative research in this rapidly evolving field.

Multifunctional nanocomposite hydrogels: an effective approach to promote diabetic wound healing

Diabetes, a metabolic disease that is becoming increasingly severe globally, presents a significant challenge in the medical field. Diabetic wounds are characterized by their chronicity, difficulty healing, and complex microenvironment that harbors multiple adverse factors, including elevated hyperglycemia, persistent inflammation, susceptibility to infections, and oxidative stress, all of which contribute to the impaired healing process. Nanocomposite hydrogels, as materials with unique physicochemical properties and biocompatibility, have gained growing attention in recent years for their potential applications in diabetic wound healing. These hydrogels provide a moist healing environment for wounds and regulate cellular behavior and signaling pathways, promoting wound repair and healing. By introducing specific functional groups and nanoparticles, nanocomposite hydrogels can respond to pathological features of wounds, enabling adaptive drug release. Owing to their diverse bioactive functions, nanocomposite hydrogels are powerful tools for the treatment of diabetic wounds. Thus, this article provides an overview of recent progress in the use of nanocomposite hydrogels for diabetic wound healing.

Pharmacokinetics-Based Design of Subcutaneous Controlled Release Systems for Biologics

Protein therapeutics have emerged as an exceedingly promising treatment modality in recent times but are predominantly given as intravenous administration. Transitioning to subcutaneous (SC) administration of these therapies could significantly enhance patient convenience by enabling at-home administration, thereby potentially reducing the overall cost of treatment. Approaches that enable sustained delivery of subcutaneously administered biologics offer further advantages in terms of less frequent dosing and better patient compliance. Controlled release technologies, such as hydrogels and subcutaneous implantable technologies, present exciting solutions by enabling the gradual release of biologics from the delivery system. Despite their substantial potential, significant hurdles remain in appropriately applying and integrating these technologies with the ongoing development of complex biologic-based therapies. We evaluate the potential impact of subcutaneously delivered controlled release systems on the downstream pharmacokinetics (PK) of several FDA-approved biologics by employing rigorous mathematical analysis and predictive PK simulations. By leveraging linear time-invariant (LTI) systems theory, we provide a robust framework for understanding and optimizing the release dynamics of these technologies. We demonstrate simple quantitative metrics and approaches that can inform the design and implementation of controlled release technologies. The findings highlight key opportunity areas to reduce dosing frequency, stabilize concentration profiles, and synergize the codelivery of biologics, calling for collaboration between drug delivery and PK scientists to create the most convenient, optimized, and effective precision therapies.

Catalytic Hybrid Lipid Nanoparticles Potentiate Circle RNA-Based Cytokine Immunotherapy

Cytokine therapeutics in cancer immunotherapy are greatly limited by their short half-time, serious toxicity, and frequent administration, which can possibly be addressed by ribonucleic acid (RNA) technology through the expression of targeting cytokines in situ. However, the intracellular translation of RNA remains restricted due to the generation of excessive reactive oxygen species (ROS) and overconsumption of adenosine triphosphate (ATP) within the transfected cells. Herein, hybrid lipid nanoparticles (Mn-LNPs) are developed by incorporating small-sized trimanganese tetraoxide nanoparticles within conventional lipid nanoparticles, showing the ability to generate oxygen, eliminate ROS, and boost intracellular ATP, thus greatly enhancing the translation efficiency. This hybrid platform is employed to encapsulate interleukin 12 (IL-12)-encoding circular RNA (Mn-LNPs@RNAIL-12) for tumor immunotherapy, exhibiting unparalleled advantages in the proliferation of cytotoxic T cells and stimulation of antitumor immunity. Moreover, the antitumor efficacy of Mn-LNPs@RNAIL-12 is further strengthened by synergizing with immune checkpoint blockade therapy to achieve durable and potent antitumor performances.

Therapeutic Potential of Injectable Supramolecular Hydrogels With Neural Stem Cell Exosomes and Hydroxypropyl Methylcellulose for Post-Stroke Neurological Recovery

Background

Stroke has significantly contributed to the global mortality rate over the years, emphasizing the urgency of finding effective treatment strategies. Neural stem cell (NSC)-derived exosomes have the potential to improve neurological recovery after stroke; however, their therapeutic efficacy is hindered by their rapid clearance and limited duration of action. This study presents an innovative drug delivery method: a hydrogel based on NSC exosomes and hydroxypropyl methylcellulose (HPMC), which is intended to offer a continuous release, thereby enhancing and prolonging neurological improvement.

Results

We developed a nanohydrogel (Exo-HPMC) by integrating Buyang Huanwu Decoction (BHD) -preconditioned NSC-derived exosomes with HPMC. This study thoroughly investigated the controlled-release capabilities and rheological properties of Exo-HPMC. Our findings show that Exo-HPMC enables effective sustained exosome release, significantly extending their retention in mice. When administered to mice with middle cerebral artery occlusion (MCAO), Exo-HPMC facilitated notable post-stroke neurorepair. Behavioral assessments and immunofluorescence staining demonstrated that exosomes significantly promoted angiogenesis and nerve regeneration in stroke-affected areas, thereby reversing programmed cell death.

Conclusion

The Exo-HPMC nanohydrogel presents a groundbreaking approach for stroke therapy. Ensuring a controlled and prolonged release of NSC-derived exosomes over two weeks, significantly enhances the therapeutic potential of exosomes for ischemic stroke treatment.

Trends in Photopolymerization 3D Printing for Advanced Drug Delivery Applications

Since its invention in the 1980s, photopolymerization-based 3D printing has attracted significant attention for its capability to fabricate complex microstructures with high precision, by leveraging light patterning to initiate polymerization and cross-linking in liquid resin materials. Such precision makes it particularly suitable for biomedical applications, in particular, advanced and customized drug delivery systems. This review summarizes the latest advancements in photopolymerization 3D printing technology and the development of biocompatible and/or biodegradable materials that have been used or shown potential in the field of drug delivery. The drug loading methods and release characteristics of the 3D printing drug delivery systems are summarized. Importantly, recent trends in the drug delivery applications based on photopolymerization 3D printing, including oral formulations, microneedles, implantable devices, microrobots and recently emerging systems, are analyzed. In the end, the challenges and opportunities in photopolymerization 3D printing for customized drug delivery are discussed.

Micelle-Containing Hydrogels and Their Applications in Biomedical Research

Hydrogels are one of the most commonly used materials in our daily lives, which possess crosslinked three-dimensional network structures and are capable of absorbing large amounts of fluid. Due to their outstanding properties, such as flexibility, tunability, and biocompatibility, hydrogels have been widely employed in biomedical research and clinics, especially in on-demand drug release. However, traditional hydrogels face various limitations, e.g., the delivery of hydrophobic drugs due to their highly hydrophilic interior environment. Therefore, micelle-containing hydrogels have been designed and developed, which possess both hydrophilic and hydrophobic microenvironments and enable the storage of diverse cargos. Based on the functionalities of micelles, these hydrogels can be classified into micelle-doped and chemically/physically crosslinked types, which were reported to be responsive to varied stimuli, including temperature, pH, irradiation, electrical signal, magnetic field, etc. Here, we summarize the research advances of micelle-containing hydrogels and provide perspectives on their applications in the biomedical field based on the recent studies from our own lab and others.

Injectable hydrogel based on liposome self-assembly for controlled release of small hydrophilic molecules

Controlled release of low molecular weight hydrophilic drugs, administered locally, allows maintenance of high concentrations at the target site, reduces systemic side effects, and improves patient compliance. Injectable hydrogels are commonly used as a vehicle. However, slow release of low molecular weight hydrophilic drugs is very difficult to achieve, mainly due to a rapid diffusion of the drug out of the drug delivery system. Here we present an injectable and self-healing hydrogel based entirely on the self-assembly of liposomes. Gelation of liposomes, without damaging their structural integrity, was induced by modifying the cholesterol content and surface charge. The small hydrophilic molecule, sodium fluorescein, was loaded either within the extra-liposomal space or encapsulated into the aqueous cores of the liposomes. This encapsulation strategy enabled the achievement of controlled and adjustable release profiles, dependent on the mechanical strength of the gel. The hydrogel had a high mechanical strength, minimal swelling, and slow degradation. The liposome-based hydrogel had prolonged mechanical stability in vivo with benign tissue reaction. This work presents a new class of injectable hydrogel that holds promise as a versatile drug delivery system. STATEMENT OF SIGNIFICANCE: The porous nature of hydrogels poses a challenge for delivering small hydrophilic drug, often resulting in initial burst release and shorten duration of release. This issue is particularly pronounced with physically crosslinked hydrogels, since their matrix can swell and dissipate rapidly, but even in cases where the polymers in the hydrogel are covalently cross-linked, small molecules can be rapidly released through its porous mesh. Here we present an injectable self-healing hydrogel based entirely on the self-assembly of liposomes. Small hydrophilic molecules were entrapped inside the extra-liposomal space or loaded into the aqueous cores of the liposomes, allowing controlled and tunable release profiles.

Review of NIR-responsive ''Smart'' carriers for photothermal chemotherapy

This review focuses on the versatile applications of near-infrared (NIR)-responsive smart carriers in biomedical applications, particularly drug delivery and photothermal chemotherapy. These carriers demonstrate multi-responsive theranostics capabilities, including pH-dependent drug release, targeted delivery of chemotherapeutics, heat-mediated drug release, and photothermal tumor damage. Biological samples are transparent to NIR light with a suitable wavelength, and therefore, NIR light is advantageous for deep-tissue penetration. It also generates sufficient heat in tissue samples, which is beneficial for on-demand NIR-responsive drug delivery in vivo systems. The development of biocompatible materials with sufficient NIR light absorption properties and drug-carrying functionality has shown tremendous growth in the last five years. Thus, this review offers insights into the current research development of NIR-responsive materials with therapeutic potential and prospects aimed at overcoming challenges to improve the therapeutic efficacy and safety in the dynamic field of NIR-responsive drug delivery.

Unzipped carbon nanotubes assisted 3D printable functionalized chitosan hydrogels for strain sensing applications

Developing multifunctional hydrogels for wearable strain sensors has received significant attention due to their diverse applications, including human motion detection, personalized healthcare, soft robotics, and human-machine interfaces. However, integrating the required characteristics into one component remains challenging. To overcome these limitations, we synthesized multifunctional hydrogels using carboxymethyl chitosan (CMCS) and unzipped carbon nanotubes (f-CNTs) as strain sensor via a one-pot strategy. The polar groups in CMCS and f-CNTs enhance the properties of the hydrogels through different interactions. The hydrogels show superior printability with a uniformity factor (U) of 0.996 ± 0.049, close to 1. The f-CNTs-assisted hydrogels showed improved storage modulus (8.8 × 105 Pa) than the pure polymer hydrogel. The hydrogels adequately adhered to different surfaces, including human skin, plastic, plastic/glass interfaces, and printed polymers. The hydrogels demonstrated rapid self-healing and good conductivity. The biocompatibility of the hydrogels was assessed using human fibroblast cells. No adverse effects were observed with hydrogels, showing their biocompatibility. Furthermore, hydrogels exhibited antibacterial potential against Escherichia coli. The developed hydrogel exhibited unidirectional motion and complex letter recognition potential with a strain sensitivity of 2.4 at 210 % strain. The developed hydrogels could explore developing wearable electronic devices for detecting human motion.

Mussel inspired sequential protein delivery based on self-healing injectable nanocomposite hydrogel

Polysaccharide based self-healing and injectable hydrogels with reversible characteristics have widespread potential in protein drug delivery. However, it is a challenge to design the dynamic hydrogel for sequential release of protein drugs. Herein, we developed a novel mussel inspired sequential protein delivery dynamic polysaccharide hydrogel. The nanocomposite hydrogel can be fabricated through doping polydopamine nanoparticles (PDA NPs) into reversible covalent bond (imine bonds) crosslinked polymer networks of oxidized hyaluronic acid (OHA) and carboxymethyl chitosan (CEC), named PDA NPs@OHA-l-CEC. Besides multiple capabilities (i.e., injection, self-healing, and biodegradability), the nanocomposite hydrogel can achieve sustained and sequential protein delivery of vascular endothelial growth factor (VEGF) and bovine serum albumin (BSA). PDA NPs doped in hydrogel matrix serve dual roles, acting as secondary protein release structures and form dynamic non-covalent interactions (i.e., hydrogen bonds) with polysaccharides. Moreover, by adjusting the oxidation degree of OHA, the hydrogels with different crosslinking density could control overall protein release rate. Analysis of different release kinetic models revealed that Fickian diffusion drove rapid VEGF release, while the slower BSA release followed a Super Case II transport mechanism. The novel biocompatible system achieved sequential release of protein drugs has potentials in multi-stage synergistic drug deliver based on dynamic hydrogel.

Injectable Granular Hydrogels Enable Avidity-Controlled Biotherapeutic Delivery

Protein therapeutics represent a rapidly growing class of pharmaceutical agents that hold great promise for the treatment of various diseases such as cancer and autoimmune dysfunction. Conventional systemic delivery approaches, however, result in off-target drug exposure and a short therapeutic half-life, highlighting the need for more localized and controlled delivery. We have developed an affinity-based protein delivery system that uses guest-host complexation between β-cyclodextrin (CD, host) and adamantane (Ad, guest) to enable sustained localized biomolecule presentation. Hydrogels were formed by the copolymerization of methacrylated CD and methacrylated dextran. Extrusion fragmentation of bulk hydrogels yielded shear-thinning and self-healing granular hydrogels (particle diameter = 32.4 ± 16.4 μm) suitable for minimally invasive delivery and with a high host capacity for the retention of guest-modified proteins. Bovine serum albumin (BSA) was controllably conjugated to Ad via EDC chemistry without affecting the affinity of the Ad moiety for CD (KD = 12.0 ± 1.81 μM; isothermal titration calorimetry). The avidity of Ad-BSA conjugates was directly tunable through the number of guest groups attached, resulting in a fourfold increase in the complex half-life (t1/2 = 5.07 ± 1.23 h, surface plasmon resonance) that enabled a fivefold reduction in protein release at 28 days. Furthermore, we demonstrated that the conjugation of Ad to immunomodulatory cytokines (IL-4, IL-10, and IFNγ) did not detrimentally affect cytokine bioactivity and enabled their sustained release. Our strategy of avidity-controlled delivery of protein-based therapeutics is a promising approach for the sustained local presentation of protein therapeutics and can be applied to numerous biomedical applications.

Integrating Fluorescence and Magnetic Resonance Imaging in Biocompatible Scaffold for Real-Time Bone Repair Monitoring and Assessment

In situ monitoring of bone tissue regeneration progression is critical for the development of bone tissue engineering scaffold. However, engineered scaffolds that can stimulate osteogenic progress and allow for non-invasive monitoring of in vivo bone regeneration simultaneously are rarely reported. Based on a hard-and-soft integration strategy, a multifunctional scaffold composed of 3D printed microfilaments and a hydrogel network containing simvastatin (SV), indocyanine green-loaded superamphiphiles, and aminated ultrasmall superparamagnetic iron oxide nanoparticles (USPIO-NH2 ) is fabricated. Both in vitro and in vivo results demonstrate that the as-prepared scaffold significantly promotes osteogenesis through controlled SV release. The biocomposite scaffold exhibits alkaline phosphatase-responsive near-infrared II fluorescence imaging. Meanwhile, USPIO-NH2 within the co-crosslinked nanocomposite network enables the visualization of scaffold degradation by magnetic resonance imaging. Therefore, the biocomposite scaffold enables or facilitates non-invasive in situ monitoring of neo-bone formation and scaffold degradation processes following osteogenic stimulation, offering a promising strategy to develop theranostic scaffolds for tissue engineering.

Elastic Macroporous Matrix-Supported In Situ Formation of Injectable Extracellular Matrix-Like Hydrogel for Carrying Growth Factors and Living Cells

Hydrogels loaded with biologics hold great potential for various biomedical applications such as regenerative medicine. However, biologics may lose bioactivity during hydrogel preparation, shipping, and storage. While many injectable hydrogels do not have this issue, they face a dilemma between fast gelation causing the difficulty of injection and slow gelation causing the escape of solutions from an injection site. The purpose of this study is to develop an affinity hydrogel by integrating a pre-formed elastic macroporous matrix and an injectable hydrogel. The data shows that the macroporous hydrogel matrix can hold a large volume of solutions for the formation of in situ injectable hydrogels loaded with growth factors or living cells. The cells can proliferate in the composite hydrogels. The growth factors can be stably sequestered and sustainably released due to the presence of aptamers. When both living cells and growth factors are loaded together into the hydrogels, cells can proliferate under culture conditions with a reduced serum level. Therefore, a macroporous and elastic matrix-supported formation of aptamer-functionalized injectable hydrogels is a promising method for developing the carriers of biologics.

Transdermal Sustained Release Properties and Anti-Photoaging Efficacy of Liposome-Thermosensitive Hydrogel System

Drug delivery systems have become a research priority in the biomedical field. The incorporation of liposomes to hydrogels further forms more robust multifunctional systems for more effective and sustained topical drug delivery. In this study, carboxymethyl-modified chitosan/hyaluronic acid (CMC/HA, CMH) thermosensitive hydrogel is developed for sustained transdermal delivery of liposomes. Hydrogels are crosslinked by hydrogen bonding, hydrophobic interaction and electrostatic interaction. The gel properties can be regulated by substitution degree (DS), and when DS = 18.20 ± 0.67% (CMH2), the gel temperature is 37.8 °C, allowing rapid gelation at body temperature (315 s). Moreover, CMH2 hydrogel has suitable spreadability (17.7-57.2 cm2 ), viscosity (2133.4 mPa s) and porous structure, which facilitated its adhesion and application on the skin and liposomes delivery. The hydrogel can retard the liposomes release, and the release rate of ascorbyl glucoside (AA2G) is 33.92-49.35% in 24 h. Hydrogel avoids the rapid clearance of liposomes from the skin and improved the skin retention, achieving the long-term release of bioactive components. Liposome-hydrogel system more efficiently promotes the anti-photoaging effect of AA2G on skin, reducing epidermal thickness, melanin deposition and lipid oxidative damage and increasing collagen density. Therefore, liposome-hydrogel systems are proposed as multifunctional delivery systems for sustained transdermal delivery.

Architecturally designed sequential-release hydrogels

Drug synergy has made significant strides in clinical applications in recent decades. However, achieving a platform that enables "single administration, multi-stage release" by emulating the natural physiological processes of the human body poses a formidable challenge in the field of molecular pharmaceutics. Hydrogels, as the novel generation of drug delivery systems, have gained widespread utilization in drug platforms owing to their exceptional biocompatibility and modifiability. Sequential drug delivery hydrogels (SDDHs), which amalgamate the advantages of hydrogel and sequential release platforms, offer a promising solution for effectively navigating the intricate human environment and accomplishing drug sequential release. Inspired by architectural design, this review establishes connections between three pivotal factors in SDDHs construction, namely mechanisms, carrier spatial structure, and stimuli-responsiveness, and three aspects of architectural design, specifically building materials, house structures, and intelligent interactive furniture, aiming at providing insights into recent developments in SDDHs. Furthermore, the dual-drug collocation and cutting-edge hydrogel preparation technologies as well as the prevailing challenges in the field were elucidated.

Injectable hydrogel particles for amorphous solid formulation of biologics

The fast pace of breakthroughs in cancer immunotherapy, combined with the new paradigm of moving toward high-concentration dosages and combinatorial treatments, is generating new challenges in the formulation of biologics. To address these challenges, we describe a method of formulation that enables high-concentration injectable and stable formulation of biologics as amorphous solids in aqueous suspension. This technology combines the benefits of liquid formulation with the stability of solid formulation and eliminates the need for drying and reconstitution. This widely applicable formulation integrates the amorphous solid forms of antibodies with the injectability, lubricity, and tunability of soft alginate hydrogel particles using a minimal process. The platform was evaluated for anti-PD-1 antibody pembrolizumab and human immunoglobulin G at concentrations up to 300 mg/mL with confirmed quality after release. The soft nature of the hydrogel matrix allowed packing the particles to high volume fractions.

Role of Hydrophobic Associations in Self-Healing Hydrogels Based on Amphiphilic Polysaccharides

Self-healing hydrogels have the ability to recover their original properties after the action of an external stress, due to presence in their structure of reversible chemical or physical cross-links. The physical cross-links lead to supramolecular hydrogels stabilized by hydrogen bonds, hydrophobic associations, electrostatic interactions, or host-guest interactions. Hydrophobic associations of amphiphilic polymers can provide self-healing hydrogels with good mechanical properties, and can also add more functionalities to these hydrogels by creating hydrophobic microdomains inside the hydrogels. This review highlights the main general advantages brought by hydrophobic associations in the design of self-healing hydrogels, with a focus on hydrogels based on biocompatible and biodegradable amphiphilic polysaccharides.

Protein Release by Controlled Desorption from Transiently Cationic Nanoparticles

Therapeutic release from hydrogels is traditionally controlled by encapsulation within nanoparticles; however, this strategy is limited for the release of proteins due to poor efficiency and denaturation. To overcome this problem, we designed an encapsulation-free release platform where negatively charged proteins are adsorbed to the exterior of transiently cationic nanoparticles, thus allowing the nanoparticles to be formulated separately from the proteins. Release is then governed by the change in nanoparticle surface charge from positive to neutral. To achieve this, we synthesized eight zwitterionic poly(lactide-block-carboxybetaine) copolymer derivatives and formulated them into nanoparticles with differing surface chemistry. The nanoparticles were colloidally stable and lost positive charge at rates dependent on the hydrolytic stability of their surface ester groups. The nanoparticles (NPs) were dispersed in a physically cross-linked hyaluronan-based hydrogel with one of three negatively charged proteins (transferrin, panitumumab, or granulocyte-macrophage colony-stimulating factor) to assess their ability to control release. For all three proteins, dispersing NPs within the gels resulted in significant attenuation of release, with the extent modulated by the hydrolytic stability of the surface groups. Release was rapid from fast-hydrolyzing ester groups, reduced with slow-hydrolyzing bulky ester groups, and very slow with nonhydrolyzing amide groups. When positively charged lysozyme was loaded into the nanocomposite gel, there was no significant attenuation of release compared to gel alone. These data demonstrate that electrostatic interactions between the protein and NP are the primary driver of protein release from the hydrogel. All released proteins retained bioactivity as determined with in vitro cell assays. This release strategy shows tremendous versatility and provides a promising new platform for controlled release of anionic protein therapeutics.

Insulin-loaded liposomes packaged in alginate hydrogels promote the oral bioavailability of insulin

Compared to subcutaneous injections, oral administration of insulin would be a preferred route of drug administration for diabetic patients. For oral delivery, both liposomes and alginate hydrogels face many challenges, including early burst release of the encapsulated drug and poor intestinal drug absorption. Also, adhesion to the intestinal mucosa remains weak, which all result in a low bioavailability of the payload. This study reports on an alginate hydrogel loaded with liposomes for oral insulin administration. Liposomes (Lip) loaded with arginine-insulin complexes (AINS) were incorporated into a hydrogel prepared from cysteine modified alginate (Cys-Alg) to form liposome-in-alginate hydrogels (AINS-Lip-Gel). An ex vivo study proves that intestinal permeation of AINS and AINS-Lip is approximately 2.0 and 6.0-fold, respectively, higher than that of free insulin. The hydrogel retarded early release of insulin (∼30%) from the liposomes and enhanced the intestinal mucosal retention. In vivo experiments revealed that the AINS-Lip-Gel released insulin in a controlled manner and possessed strong hypoglycemic effects. We conclude that liposome-in-alginate hydrogels loaded with AINS represent an attractive strategy for the oral delivery of insulin.

Advanced Formulations/Drug Delivery Systems for Subcutaneous Delivery of Protein-Based Biotherapeutics

Multiple advanced formulations and drug delivery systems (DDSs) have been developed to deliver protein-based biotherapeutics via the subcutaneous (SC) route. These formulations/DDSs include high-concentration solution, co-formulation of two or more proteins, large volume injection, protein cluster/complex, suspension, nanoparticle, microparticle, and hydrogel. These advanced systems provide clinical benefits related to efficacy and safety, but meanwhile, have more complicated formulations and manufacturing processes compared to conventional solution formulations. To develop a fit-for-purpose formulation/DDS for SC delivery, scientists need to consider multiple factors, such as the primary indication, targeted site, immunogenicity, compatibility, biopharmaceutics, patient compliance, etc. Next, they need to develop appropriate formulation (s) and manufacturing processes using the QbD principle and have a control strategy. This paper aims to provide a comprehensive review of advanced formulations/DDSs recently developed for SC delivery of proteins, as well as some knowledge gaps and potential strategies to narrow them through future research.