Synthetic networks with tunable responsiveness, biodegradation, and molecular recognition for precision medicine applications

Biodegradable Covalently Crosslinked Poly[N-(2-Hydroxypropyl) Methacrylamide] Nanogels: Preparation and Physicochemical Properties

Recently, suitably sized polymer-based nanogels containing functional groups for the binding of biologically active substances and ultimately degradable to products that can be removed by glomerular filtration have become extensively studied systems in the field of drug delivery. Herein, we designed and tailored the synthesis of hydrophilic and biodegradable poly[N-(2-hydroxypropyl) methacrylamide-co-N,N'-bis(acryloyl) cystamine-co-6-methacrylamidohexanoyl hydrazine] (PHPMA-BAC-BMH) nanogels. The facile and versatile dispersion polymerization enabled the preparation of nanogels with a diameter below 50 nm, which is the key parameter for efficient and selective passive tumor targeting. The effects of the N,N'-bis(acryloyl) cystamine crosslinker, polymerization composition, and medium including H2O/MetCel and H2O/EtCel on the particle size, particle size distribution, morphology, and polymerization kinetics and copolymer composition were investigated in detail. We demonstrated the formation of a 38 nm colloidally stable PHPMA-BAC-BMH nanogel with a core-shell structure that can be rapidly degraded in the presence of 10 mM glutathione solution under physiologic conditions. The nanogels were stable in an aqueous solution modeling the bloodstream; thus, these nanogels have the potential to become highly important carriers in the drug delivery of various molecules.

Molecular targets, therapeutic agents and multitasking nanoparticles to deal with cancer stem cells: A narrative review

There is increasing evidence that malignant tumors are initiated and maintained by a sub-population of tumor cells that have similar biological properties to normal adult stem cells. This very small population of Cancer Stem Cells (CSC) comprises tumor initiating cells responsible for cancer recurrence, drug resistance and metastasis. Conventional treatments such as chemotherapy, radiotherapy and surgery, in addition to being potentially toxic and non-specific, may paradoxically increase the population, spread and survival of CSCs. Next-generation sequencing and omics technologies are increasing our understanding of the pathways and factors involved in the development of CSCs, and can help to discover new therapeutic targets against CSCs. In addition, recent advances in nanomedicine have provided hope for the development of optimal specific therapies to eradicate CSCs. Moreover, the use of artificial intelligence and nano-informatics can elucidate new drug targets, and help to design drugs and nanoparticles (NPs) to deal with CSCs. In this review, we first summarize the properties of CSCs and describe the signaling pathways and molecular characteristics responsible for the emergence and survival of CSCs. Also, the location of CSCs within the tumor and the effect of host factors on the creation and maintenance of CSCs are discussed. Newly discovered molecular targets involved in cancer stemness and some novel therapeutic compounds to combat CSCs are highlighted. The optimum properties of anti-CSC NPs, including blood circulation and stability, tumor accumulation and penetration, cellular internalization, drug release, endosomal escape, and aptamers designed for specific targeting of CSCs are covered. Finally, some recent smart NPs designed for therapeutic and theranostic purposes to overcome CSCs are discussed.

Green Synthesis of Metal and Metal Oxide Nanoparticles: A Review of the Principles and Biomedical Applications

In recent years, interest in nanotechnology has increased exponentially due to enhanced progress and technological innovation. In tissue engineering, the development of metallic nanoparticles has been amplified, especially due to their antibacterial properties. Another important characteristic of metal NPs is that they enable high control over the features of the developed scaffolds (optimizing their mechanical strength and offering the controlled release of bioactive agents). Currently, the main concern related to the method of synthesis of metal oxide NPs is the environmental impact. The physical and chemical synthesis uses toxic agents that could generate hazards or exert carcinogenicity/environmental toxicity. Therefore, a greener, cleaner, and more reliable approach is needed. Green synthetic has come as a solution to counter the aforementioned limitations. Nowadays, green synthesis is preferred because it leads to the prevention/minimization of waste, the reduction of derivatives/pollution, and the use of non-toxic (safer) solvents. This method not only uses biomass sources as reducing agents for metal salts. The biomolecules also cover the synthesized NPs or act as in situ capping and reducing agents. Further, their involvement in the formation process reduces toxicity, prevents nanoparticle agglomeration, and improves the antimicrobial activity of the nanomaterial, leading to a possible synergistic effect. This study aims to provide a comprehensive review of the green synthesis of metal and metal oxide nanoparticles, from the synthesis routes, selected solvents, and parameters to their latest application in the biomedical field.

Recent advances in glucose oxidase-based nanocarriers for tumor targeting therapy

Glucose oxidase (GOx) can specifically catalyze the conversion of β-d-glucose into gluconic acid and hydrogen peroxide (H2O2) in the presence of oxygen, making it promising for tumor starvation therapy and oxidative therapy. However, GOx's immunogenicity, poor in vivo stability, short half-life, and potential systemic toxicity, limit its application in cancer therapy. Nanocarriers are capable of improving the pharmacological properties of therapeutic drugs (e.g. stability, circulating half-life, and tumor accumulation) and lower toxicity, hence resolving GOx issues and enhancing its efficacy. Although the application of targeted nanocarriers based on GOx has recently flourished, this field has not yet been reviewed and evaluated. Herein, we initially examined the mechanism of GOx-based nanocarriers for enhanced tumor therapy. Also, we present a comprehensive and up-to-date review that highlights GOx-based nanocarriers for tumor targeting therapy. This review expands on GOx-based nano-targeted combination therapies from both passive and active targeting perspectives, meanwhile, active targeting is further classified into ligand-mediated targeting and physical-mediated targeting. Furthermore, this review also emphasizes the present challenges and promising advancements.

Versatile Tissue-Injectable Hydrogels with Extended Hydrolytic Release of Bioactive Protein Therapeutics

Hydrogels generally have broad utilization in healthcare due to their tunable structures, high water content, and inherent biocompatibility. FDA-approved applications of hydrogels include spinal cord regeneration, skin fillers, and local therapeutic delivery. Drawbacks exist in the clinical hydrogel space, largely pertaining to inconsistent therapeutic exposure, short-lived release windows, and difficulties inserting the polymer into tissue. In this study, we engineered injectable, biocompatible hydrogels that function as a local protein therapeutic depot with a high degree of user-customizability. We showcase a PEG-based hydrogel functionalized with bioorthogonal strain-promoted azide-alkyne cycloaddition (SPAAC) handles for its polymerization and functionalization with a variety of payloads. Small-molecule and protein cargos, including chemokines and antibodies, were site-specifically modified with hydrolysable "azidoesters" of varying hydrophobicity via direct chemical conjugation or sortase-mediated transpeptidation. These hydrolysable esters afforded extended release of payloads linked to our hydrogels beyond diffusion; with timescales spanning days to months dependent on ester hydrophobicity. Injected hydrogels polymerize in situ and remain in tissue over extended periods of time. Hydrogel-delivered protein payloads elicit biological activity after being modified with SPAAC-compatible linkers, as demonstrated by the successful recruitment of murine T-cells to a mouse melanoma model by hydrolytically released murine CXCL10. These results highlight a highly versatile, customizable hydrogel-based delivery system for local delivery of protein therapeutics with payload release profiles appropriate for a variety of clinical needs.

Injectable, self-healing hydrogel adhesives with firm tissue adhesion and on-demand biodegradation for sutureless wound closure

Tissue adhesives have garnered extensive interest as alternatives and supplements to sutures, whereas major challenges still remain, including weak tissue adhesion, inadequate biocompatibility, and uncontrolled biodegradation. Here, injectable and biocompatible hydrogel adhesives are developed via catalyst-free o-phthalaldehyde/amine (hydrazide) cross-linking reaction. The hydrogels demonstrate rapid and firm adhesion to various tissues, and an o-phthalaldehyde-mediated tissue adhesion mechanism is established. The hydrogel adhesives show controlled degradation profiles of 6 to 22 weeks in vivo through the incorporation of disulfide bonds into hydrogel network. In liver and blood vessel injury, the hydrogels effectively seal the incisions and rapidly stop bleeding. In rat and rabbit models of full-thickness skin incision, the hydrogel adhesives quickly close the incisions and accelerate wound healing, which exhibit efficacies superior to those of commercially available fibrin glue and cyanoacrylate glue. Thus, the hydrogel adhesives show great potential for sutureless wound closure, hemostasis sealing, and prevention of leakage in surgical applications.

Protease-Responsive Hydrogel Microparticles for Intradermal Drug Delivery

Protease-responsive multi-arm polyethylene glycol-based microparticles with biscysteine peptide crosslinkers (CGPGG↓LAGGC) were obtained for intradermal drug delivery through inverse suspension photopolymerization. The average size of the spherical hydrated microparticles was ∼40 μm after crosslinking, making them attractive as a skin depot and suitable for intradermal injections, as they are readily dispensable through 27G needles. The effects of exposure to matrix metalloproteinase 9 (MMP-9) on the microparticles were evaluated by scanning electron microscopy and atomic force microscopy, demonstrating partial network destruction and decrease in elastic moduli. Given the recurring course of many skin diseases, the microparticles were exposed to MMP-9 in a flare-up mimicking fashion (multiple-time exposure), showing a significant increase in release of tofacitinib citrate (TC) from the MMP-responsive microparticles, which was not seen for the non-responsive microparticles (polyethylene glycol dithiol crosslinker). It was found that the degree of multi-arm complexity of the polyethylene glycol building blocks can be utilized to tune not only the release profile of TC but also the elastic moduli of the hydrogel microparticles, with Young's moduli ranging from 14 to 140 kPa going from 4-arm to 8-arm MMP-responsive microparticles. Finally, cytotoxicity studies conducted with skin fibroblasts showed no reduction in metabolic activity after 24 h exposure to the microparticles. Overall, these findings demonstrate that protease-responsive microparticles exhibit the properties of interest for intradermal drug delivery.

Synthesis of zwitterionic polyelectrolyte nanogels via electrostatic-templated polymerization

Zwitterionic polyelectrolyte nanogels are prospective nanocarriers due to their soft loading pocket and regulated charges. We here report a facile strategy, namely, electrostatic-templated polymerization (ETP) for synthesizing zwitterionic nanogels with controlled size and properties. Specifically, with anionic-neutral diblock polymers as the template, zwitterionic monomers such as carboxybetaine methacrylate (CBMA) or carboxybetaine acrylamide (CBAA) are polymerized together with a cross-linker at pH 2 where the monomers exhibit only positive charge due to the protonation of the carboxyl group. The obtained polyelectrolyte complex micelles dissociate upon introducing a concentrated salt. The subsequent separation yields the released template and zwitterionic nanogels with regulated size and swelling ability, achieved by tuning the salt concentration and cross-linker fraction during polymerization. The obtained PCBMA nanogels exhibit charges depending on the pH, which enables not only the selective loading of different dye molecules, but also encapsulation and intracellular delivery of cytochrome c protein. Our study develops a facile and robust way for fabricating zwitterionic nanogels and validates their potential applications as promising nanocarriers for load and delivery of functional charged cargos.

Design of Synthetic Hydrogel Compositions for Noncovalent Protein Recognition

Multifunctional hydrogels composed of segments with ionizable, hydrophilic, and hydrophobic monomers have been optimized for sensing, bioseparation, and therapeutic applications. While the "biological identity" of bound proteins from biofluids underlies device performance in each context, design rules that predict protein binding outcomes from hydrogel design parameters are lacking. Uniquely, hydrogel designs that influence protein affinity (e.g., ionizable monomers, hydrophobic moieties, conjugated ligands, cross-linking) also affect physical properties (e.g., matrix stiffness, volumetric swelling). Here, we evaluated the influence of hydrophobic comonomer steric bulk and quantity on the protein recognition characteristics of ionizable microscale hydrogels (microgels) while controlling for swelling. Using a library synthesis approach, we identified compositions that balance the practical balance between protein-microgel affinity and the loaded mass at saturation. Intermediate quantities (10-30 mol %) of hydrophobic comonomer increased the equilibrium binding of certain model proteins (lysozyme, lactoferrin) in buffer conditions that favored complementary electrostatic interactions. Solvent-accessible surface area analysis of model proteins identified arginine content as highly predictive of model proteins' binding to our library of hydrogels containing acidic and hydrophobic comonomers. Taken together, we established an empirical framework for characterizing the molecular recognition properties of multifunctional hydrogels. Our study is the first to identify solvent-accessible arginine as an important predictor for protein binding to hydrogels containing both acidic and hydrophobic subunits.

Self-Therapeutic Nanomaterials: Applications in Biology and Medicine

Over past decades, nanotechnology has contributed to the biomedical field in areas including detection, diagnosis, and drug delivery via opto-electronic properties or enhancement of biological effects. Though generally considered inert delivery vehicles, a plethora of past and present evidence demonstrates that nanomaterials also exude unique intrinsic biological activity based on composition, shape, and surface functionalization. These intrinsic biological activities, termed self-therapeutic properties, take several forms, including mediation of cell-cell interactions, modulation of interactions between biomolecules, catalytic amplification of biochemical reactions, and alteration of biological signal transduction events. Moreover, study of biomolecule-nanomaterial interactions offers a promising avenue for uncovering the molecular mechanisms of biology and the evolution of disease. In this review, we observe the historical development, synthesis, and characterization of self-therapeutic nanomaterials. Next, we discuss nanomaterial interactions with biological systems, starting with administration and concluding with elimination. Finally, we apply this materials perspective to advances in intrinsic nanotherapies across the biomedical field, from cancer therapy to treatment of microbial infections and tissue regeneration. We conclude with a description of self-therapeutic nanomaterials in clinical trials and share our perspective on the direction of the field in upcoming years.

Biosynthesized Gold, Silver, Palladium, Platinum, Copper, and Other Transition Metal Nanoparticles

Nanomedicine is a potential provider of novel therapeutic and diagnostic routes of treatment. Considering the development of multidrug resistance in pathogenic bacteria and the commonness of cancer, novel approaches are being sought for the safe and efficient synthesis of new nanoparticles, which have multifaceted applications in medicine. Unfortunately, the chemical synthesis of nanoparticles raises justified environmental concerns. A significant problem in their widespread use is also the toxicity of compounds that maintain nanoparticle stability, which significantly limits their clinical use. An opportunity for their more extensive application is the utilization of plants, fungi, and bacteria for nanoparticle biosynthesis. Extracts from natural sources can reduce metal ions in nanoparticles and stabilize them with non-toxic extract components.

Sequentially Activatable Polypeptide Nanoparticles for Combinatory Photodynamic Chemotherapy of Breast Cancer

Stimuli-activatable nanomaterials hold significant promise for tumor-specific drug delivery by recognizing the internal or external stimulus. Herein, we reported a dual-responsive and biodegradable polypeptide nanoparticle (PPTP@PTX₂ NP) for combinatory chemotherapy and photodynamic therapy (PDT) of breast cancer. The NPs were engineered by encapsulating diselenide bond linked dimeric prodrug of paclitaxel (PTX₂) in an intracellular acidity-activatable polypeptide micelle. Specifically, the acid-responsive polypeptide was synthesized by grafting a tetraphenyl porphyrin (TPP) photosensitizer and N,N-diisopropylethylenediamine (DPA) onto the poly(ethylene glycol)-block-poly(glutamic acid) diblock copolymer by the amidation reaction, which self-assembled into micellar NPs and was activated inside the acidic endocytic vesicles to perform PDT. The paclitaxel dimer can be stably loaded into the polypeptide NPs and be restored by PDT inside the tumor cells. The formed PPTP@PTX₂ NPs remained inert during blood circulation and passively accumulated in the tumor foci, which could be activated within the endocytic vesicles via acid-triggered protonation of DPA groups to generate fluorescence signal and release PTX₂ in 4T1 murine breast tumor cells. Upon 660 nm laser irradiation, the activated NPs carried out PDT via TPP and chemotherapy via PTX to induce apoptosis of 4T1 cells and thereby efficiently inhibited 4T1 tumor growth and prevented metastasis of tumor cells.

Controlled Covalent Self-Assembly of a Homopolymer for Multiscale Materials Engineering

Polymer self-assembly is a crucial process in materials engineering. Currently, almost all polymer self-assembly is limited to non-covalent bonding methods, even though these methods have drawbacks as they require complicated synthesis techniques and produce relatively unstable structures. Here, a novel mechanism of covalent polymer self-assembly is discovered and employed to address drawbacks of non-covalent polymer self-assembly. A simple ketone homopolymer is found to self-assemble into nano- to macroscale hydrogels during covalent crosslinking. In contrast to non-covalent self-assembly, the covalent self-assembly is independent of and unaffected by solvent conditions (e.g., polarity and ionic strength) and does not require additional agents, e.g., organic solvents and surfactants. The covalent polymer self-assembly is subjected to a new mechanism of control by tuning the covalent crosslinking rate. This leads to nanogels with an unprecedented and tightly controlled range of dimensions from less than 10 nm to above 100 nm. Moreover, the crosslinking rate also regulates the assembly behavior of microgels fabricated by microfluidics. The microgels self-assemble into granular fibers, which is 3D printed into stable porous scaffolds. The novel covalent polymer assembly method has enormous potential to revolutionize multiscale materials fabrication for applications in drug delivery, tissue engineering, and many other fields.

Bioengineered nanogels for cancer immunotherapy

Recent years have witnessed increasingly rapid advances in nanocarrier-based biomedicine aimed at improving treatment paradigms for cancer. Nanogels serve as multipurpose and constructed vectors formed via intramolecular cross-linking to generate drug delivery systems, which is attributed predominantly to their satisfactory biocompatibility, bio-responsiveness, high stability, and low toxicity. Recently, immunotherapy has experienced unprecedented growth and has become the preferred strategy for cancer treatment, and mainly involves the mobilisation of the immune system and an enhanced anti-tumour immunity of the tumour microenvironment. Despite the inspiring success, immunotherapeutic strategies are limited due to the low response rates and immune-related adverse events. Like other nanomedicines, nanogels are comparably limited by lower focal enrichment rates upon introduction into the organism via injection. Because nanogels are three-dimensional cross-linked aqueous materials that exhibit similar properties to natural tissues and are structurally stable, they can comfortably cope with shear forces and serum proteins in the bloodstream, and the longer circulation life increases the chance of nanogel accumulation in the tumour, conferring deep tumour penetration. The large specific surface area can reduce or eliminate off-target effects by introducing stimuli-responsive functional groups, allowing multiple physical and chemical modifications for specific purposes to improve targeting to specific immune cell subpopulations or immune organs, increasing the bioavailability of the drug, and conferring a low immune-related adverse events on nanogel therapies. The slow release upon reaching the tumour site facilitates long-term awakening of the host's immune system, ultimately achieving enhanced therapeutic effects. As an effective candidate for cancer immunotherapy, nanogel-based immunotherapy has been widely used. In this review, we mainly summarize the recent advances of nanogel-based immunotherapy to deliver immunomodulatory small molecule drugs, antibodies, genes and cytokines, to target antigen presenting cells, form cancer vaccines, and enable chimeric antigen receptor (CAR)-T cell therapy. Future challenges as well as expected and feasible prospects for clinical treatment are also highlighted.

An Overview of the Importance of Transition-Metal Nanoparticles in Cancer Research

Several authorities have implied that nanotechnology has a significant future in the development of advanced cancer therapies. Nanotechnology makes it possible to simultaneously administer drug combinations and engage the immune system to fight cancer. Nanoparticles can locate metastases in different organs and deliver medications to them. Using them allows for the effective reduction of tumors with minimal toxicity to healthy tissue. Transition-metal nanoparticles, through Fenton-type or Haber-Weiss-type reactions, generate reactive oxygen species. Through oxidative stress, the particles induce cell death via different pathways. The main limitation of the particles is their toxicity. Certain factors can control toxicity, such as route of administration, size, aggregation state, surface functionalization, or oxidation state. In this review, we attempt to discuss the effects and toxicity of transition-metal nanoparticles.

Synthesis of Anionic Nanogels for Selective and Efficient Enzyme Encapsulation

Polyelectrolyte nanogels containing cross-linked ionic polymer networks feature both soft environment and intrinsic charges which are of great potential for enzyme encapsulation. In this work, well-defined poly(acrylic acid) (PAA) nanogels have been synthesized based on a facile strategy, namely, electrostatic assembly directed polymerization (EADP). Specifically, AA monomers are polymerized together with a cross-linker in the presence of a cationic-neutral diblock copolymer as the template. Effects of control factors including pH, salt concentration, and cross-linking degree have been investigated systematically, based on which the optimal preparation of PAA nanogels has been established. The obtained nanogel features not only compatible pocket for safely loading enzymes without disturbing their structures, but also abundant negative charges which enable selective and efficient encapsulation of cationic enzymes. The loading capacities of PAA nanogels for cytochrome (cyt c) and lysozyme are 100 and 125 μg/mg (enzyme/nanogel), respectively. More notably, the PAA network seems to modulate a favorable microenvironment for cyt c and induces 2-fold enhanced activity for the encapsulated enzymes, as indicated by the steady-state kinetic assay. Our study reveals the control factors of EADP for optimal synthesis of anionic nanogels and validates their distinctive advances with respect to efficient loading and activation of cationic enzymes.

Upgrading of bio‐separation and bioanalysis using synthetic polymers: Molecularly imprinted polymers (MIPs), cryogels, stimuli‐responsive polymers

Bio‐separation plays a crucial role in many areas. Different polymers are suitable for bio‐separation and are useful for applications in applications in both science and technology. Besides biopolymers, there are a broad spectrum of synthetic polymers with tailor‐made properties. The synthetic polymers are characterized by their charges, solubility, hydrophilicity/hydrophobicity, sensitivity to environmental conditions and stability. Furthermore, ongoing developments are of great interest on biodegradable polymers for the treatment of diseases. Smart polymers have gained great attention due to their unique characteristics especially emphasizing simultaneously changing their chemical and physical property upon exposure to changes in environmental conditions. In this review, methodologies applied in bio‐separation using synthetic polymers are discussed and efficient candidates are focused for the construction of synthetic polymers.

Epitope-imprinted polymers: Design principles of synthetic binding partners for natural biomacromolecules

Molecular imprinting (MI) has been explored as an increasingly viable tool for molecular recognition in various fields. However, imprinting of biologically relevant molecules like proteins is severely hampered by several problems. Inspired by natural antibodies, the use of epitopes as imprinting templates has been explored to circumvent those limitations, offering lower costs and greater versatility. Here, we review the latest innovations in this technology, as well as different applications where MI polymers (MIPs) have been used to target biomolecules of interest. We discuss the several steps in MI, from the choice of epitope and functional monomers to the different production methods and possible applications. We also critically explore how MIP performance can be assessed by various parameters. Last, we present perspectives on future breakthroughs and advances, offering insights into how MI techniques can be expanded to new fields such as tissue engineering.

Extracellular Vesicle Nanoarchitectonics for Novel Drug Delivery Applications

Extracellular vesicles (EVs) can transfer intercellular messages in various (patho)physiological processes and transport biomolecules to recipient cells. EVs possess the capacity to evade the immune system and remain stable over long periods, identifying them as natural carriers for drugs and biologics. However, the challenges associated with EVs isolation, heterogeneity, coexistence with homologous biomolecules, and lack of site-specific delivery, have impeded their potential. In recent years, the amalgamation of EVs with rationally engineered nanostructures has been proposed for achieving effective drug loading and site-specific delivery. With the advancement of nanotechnology and nanoarchitectonics, different nanostructures with tunable size, shapes, and surface properties can be integrated with EVs for drug loading, target binding, efficient delivery, and therapeutics. Such integration may enable improved cellular targeting and the protection of encapsulated drugs for enhanced and specific delivery to target cells. This review summarizes the recent development of nanostructure amalgamated EVs for drug delivery, therapeutics, and real-time monitoring of disease progression. With a specific focus on the exosomal cargo, diverse drug delivery system, and biomimetic nanostructures based on EVs for selective drug delivery, this review also chronicles the needs and challenges of EV-based biomimetic nanostructures and provides a future outlook on the strategies posed.

Charged Poly(N-isopropylacrylamide) Nanogels for the Stabilization of High Isoelectric Point Proteins

Storage and transportation of protein therapeutics using refrigeration is a costly process; a reliable electrical supply is vital, expensive equipment is needed, and unique transportation is required. Reducing the reliance on the cold chain would enable low-cost transportation and storage of biologics, ultimately improving accessibility of this class of therapeutics to patients in remote locations. Herein, we report on the synthesis of charged poly(N-isopropylacrylamide) nanogels that efficiently adsorb a range of different proteins of varying isoelectric points and molecular weights (e.g., adsorption capacity (Q) = 4.7 ± 0.2 mg/mg at 6 mg/mL initial IgG concentration), provide protection from external environmental factors (i.e., temperature), and subsequently release the proteins in an efficient manner (e.g., 100 ± 1% at 2 mg/mL initial IgG concentration). Both cationic and anionic nanogels were synthesized and selectively chosen based on the ability to form electrostatic interactions with adsorbed proteins (e.g., cationic nanogels adsorb low isoelectric point proteins whereas anionic nanogels adsorb high isoelectric point proteins). The nanogel-protein complex formed upon adsorption increases the stabilization of the protein's tertiary structure, providing protection against denaturation at elevated temperatures (e.g., 84 ± 4% of the protected IgG was stabilized when exposed to 65 °C). The addition of a high molar salt solution (e.g., 40 mM CaCl₂ solution) to protein-laden nanogels disrupts the electrostatic interactions and collapses the nanogel, ultimately releasing the protein. The versatile materials utilized, in addition to the protein loading and release mechanisms described, provide a simple and efficient strategy to protect fragile biologics for their transport to remote areas without necessitating costly storage equipment.

Theranostic biomaterials for tissue engineering

Tissue engineering strategies, notably biomaterials, can be modularly designed and tuned to match specific patient needs. Although many challenges within tissue engineering remain, the incorporation of diagnostic strategies to create theranostic (combined therapy and diagnostic) biomaterials presents a unique platform to provide dual monitoring and treatment capabilities and advance the field toward personalized technologies. In this review, we summarize recent developments in this young field of regenerative theranostics and discuss the clinical potential and outlook of these systems from a tissue engineering perspective. As the need for precision and personalized medicines continues to increase to address diseases in all tissues in a patient-specific manner, we envision that such theranostic platforms can serve these needs.

Safe and efficient 2D molybdenum disulfide platform for cooperative imaging-guided photothermal-selective chemotherapy: A preclinical study

•

Safe and efficient platform of TOS married MoS₂ is synthesized by judicious designed for multimode theranostics of ovarian carcinoma.

•

A photothermal conversion efficiency of 65.3% of the platform is higher than that of other materials reported elsewhere.

•

Highly efficient photothermal ablation under safe irradiation and significantly improved selective chemotherapy for tumor.

•

Synergistic therapy, suppressed recurrence, and negligible side effects enable the prominent survival rate of 100% over 91 days for the tumor-bearing mice.

•

A promising candidate for precise nanomedicines in clinical translation.

Introduction

The striking imbalance between the ever-increasing amount of nanomedicines and low clinical translation of products has become the focus of intense debate. For clinical translation, the critical issue is to select the appropriate agents and combination regimen for targeted diseases, not to prepare increasingly complex nanoplatforms.

Objectives

A safe and efficient platform, α-tocopheryl succinate (α-TOS) married 2D molybdenum disulfide, was devised by a facile method and applied for cooperative imaging-guided photothermal-selective chemotherapy of ovarian carcinoma.

Methods

A novel platform of PEGylated α-TOS and folic acid (FA) conjugated 2D MoS₂ nanoflakes was fabricated  for the cooperative multimode computed tomography (CT)/photoacoustic (PA)/thermal imaging-guided photothermal-selective chemotherapy of ovarian carcinoma.

Results

The photothermal efficiency (65.3%) of the platform under safe near-infrared irradiation is much higher than that of other photothermal materials reported elsewhere. Moreover, the covalently linked α-TOS renders platform with selective chemotherapy for cancer cells. Remarkably, with these excellent properties, the platform can be used to completely eliminate the solid tumor by safe photothermal therapy, and then kill the residual cancer cells by selective chemotherapy to prevent tumor recurrence. More significantly, barely side effects occur in the whole treatment process. The excellent efficacy and safety benefits in vivo lead to the prominent survival rate of 100% over 91 days.

Conclusion

The safe and efficient platform might be a candidate of clinical nanomedicines for multimode theranostics. This study demonstrates an innovative thought in precise nanomedicine regarding the design of next generation of cancer theranostic protocol for potential clinical practice.

DNA-Scaffolded Disulfide Redox Network for Programming Drug-Delivery Kinetics

In response to specific stimuli, dynamic covalent materials enable the generation of new structures by reversibly forming/breaking chemical bonds, thus showing great potential for application in controlled drug release. However, using dynamic covalent chemistry to program drug-delivery kinetics remains challenging. Herein, an in situ polymerization-generated DNA-scaffolded disulfide redox network (DdiSRN) is reported in which nucleic acids are used as a scaffold for dynamic disulfide bonds. The constructed DdiSRN allows selective release of loading cargos inside cancer cells in response to redox stimuli. Moreover, the density of disulfide bonds in network can be tuned by precise control over their position and number on DNA scaffolds. As a result, drug-delivery kinetics can be programmed with a half-life, t_1/2 , decreasing from 8.3 to 4.4 h, thus facilitating keeping an adequate drug concentration within the therapeutic window. Both in vitro and in vivo studies confirm that co-delivery of DOX and siRNA in combination with fast drug release inside cells using this DdiSRN enhances the therapeutic effect on multidrug-resistant cancer. This nontrivial therapeutic platform enabling kinetic control provides a good paradigm for precision cancer medicine.

Recent applications of QCM-D for the design, synthesis, and characterization of bioactive materials

The clinical translation of bioactive technologies is lacking compared to the number of novel technologies reported in the literature. This is in part due to the difficulties in characterizing bioactive materials to understand and predict their biological response. To progress the field and increase clinical success, more robust analytical techniques must be utilized when investigating novel bioactive materials. The quartz crystal microbalance with dissipation (QCM-D), a label-free sensing instrument based on an acoustic resonator, is used to quantify mass change and viscoelastic parameters from soft materials at the nanoscale, in situ, with precise temporal resolution and operation in both liquid and gaseous environments. The versatility of QCM-D has enhanced the characterization of bioactive polymers and sensing arrays for advanced applications of novel biotechnologies. In this review, we highlight exciting, recent applications of QCM-D for the investigation of bioactive materials. Attention is given to the dynamic mechanical properties of bioactive materials, discerning protein structure on surfaces, probing cell adhesion and cytoskeletal changes, and biosensing applications. We conclude that QCM-D has untapped utility in the pre-clinical investigation of bioactive materials and further utilization can improve the clinical success of novel technologies.

Optimal synthesis of polyelectrolyte nanogels by electrostatic assembly directed polymerization for dye loading and release

Polyelectrolyte (PE) nanogels which combine features of nanogels and polyelectrolytes have attracted significant attention as outstanding nano-carriers. However, and crucially, any large-scale application of PE nanogels can only materialize when an efficient production method is available. We recently developed such a robust approach, namely Electrostatic Assembly Directed Polymerization (EADP), in which ionic monomers are polymerized together with cross-linker in the presence of a polyion-neutral diblock copolymer as template. Although EADP achieves efficient and scalable preparation of diverse PE nanogels, the essential factors for the optimal and controlled synthesis of nanogels have remained elusive. In this article, we investigate systematically the effects of pH, salt concentration, and cross-linker fractions on the formation and properties of a PDMAEMA nanogel prepared with PAA-b-PEO as the template. We find that the electrostatic interaction between the building blocks is crucial to obtain assembly-controlled polymerization, and we establish preferred pH, salt concentration and cross-linker fractions. The obtained PDMAEMA nanogel exhibits dual-responses to pH and salt, which allow manipulation of the positive charges of the nanogels for selective loading and controlled release of anionic substances; we demonstrate this with an anionic dye. The study presented here fully addresses the process parameters of EADP regarding optimal and controlled preparation of PE nanogels, which should allow exploration of their potential vis-a-vis a variety of applications.

Photoacoustic Cavitation-Ignited Reactive Oxygen Species to Amplify Peroxynitrite Burst by Photosensitization-Free Polymeric Nanocapsules

Photoacoustic (PA) technology can transform light energy into acoustic wave, which can be used for either imaging or therapy that depends on the power density of pulsed laser. Here, we report photosensitizer-free polymeric nanocapsules loaded with nitric oxide (NO) donors, namely NO-NCPs, formulated from NIR light-absorbable amphiphilic polymers and a NO-releasing donor, DETA NONOate. Controlled NO release and nanocapsule dissociation are achieved in acidic lysosomes of cancer cells. More importantly, upon pulsed laser irradiation, the PA cavitation can excite water to generate significant reactive oxygen species (ROS) such as superoxide radical (O₂ ^.- ), which further spontaneously reacts with the in situ released NO to burst highly cytotoxic peroxynitrite (ONOO^- ) in cancer cells. The resultant ONOO^- generation greatly promotes mitochondrial damage and DNA fragmentation to initiate programmed cancer cell death. Apart from PA imaging, PA cavitation can intrinsically amplify reactive species via photosensitization-free materials for promising disease theranostics.

Engineering precision nanoparticles for drug delivery

In recent years, the development of nanoparticles has expanded into a broad range of clinical applications. Nanoparticles have been developed to overcome the limitations of free therapeutics and navigate biological barriers — systemic, microenvironmental and cellular — that are heterogeneous across patient populations and diseases. Overcoming this patient heterogeneity has also been accomplished through precision therapeutics, in which personalized interventions have enhanced therapeutic efficacy. However, nanoparticle development continues to focus on optimizing delivery platforms with a one-size-fits-all solution. As lipid-based, polymeric and inorganic nanoparticles are engineered in increasingly specified ways, they can begin to be optimized for drug delivery in a more personalized manner, entering the era of precision medicine. In this Review, we discuss advanced nanoparticle designs utilized in both non-personalized and precision applications that could be applied to improve precision therapies. We focus on advances in nanoparticle design that overcome heterogeneous barriers to delivery, arguing that intelligent nanoparticle design can improve efficacy in general delivery applications while enabling tailored designs for precision applications, thereby ultimately improving patient outcome overall.

Advances in nanoparticle design could make substantial contributions to personalized and non-personalized medicine. In this Review, Langer, Mitchell, Peppas and colleagues discuss advances in nanoparticle design that overcome heterogeneous barriers to delivery, as well as the challenges in translating these design improvements into personalized medicine approaches.

Peptide conjugation enhances the cellular co-localization, but not endosomal escape, of modular poly(acrylamide-co-methacrylic acid) nanogels

Nanoparticles must recognize, adhere to, and/or traverse multiple barriers in sequence to achieve cytosolic drug delivery. New nanoparticles often exhibit a unique ability to cross a single barrier (i.e. the vasculature, cell membrane, or endosomal compartment), but fail to deliver an adequate dose to intracellular sites of action because they cannot traverse other biological barriers for which they were not optimized. Here, we developed poly(acrylamide-co-methacrylic acid) nanogels that were modified in a modular manner with bioactive peptides. This nanogel does not recognize target cells or disrupt endosomal vesicles in its unmodified state, but can incorporate peptides with molecular recognition or environmentally responsive properties. Nanogels were modified with up to 15 wt% peptide without significantly altering their size, surface charge, or stability in aqueous buffer. Nanogels modified with a colon cancer-targeting oligopeptide exhibited up to a 324% enhancement in co-localization with SW-48 colon cancer cells in vitro, while influencing nanogel uptake by fibroblasts and macrophages to a lesser extent. Nanogels modified with an endosome disrupting peptide failed to retain its native endosomolytic activity, when coupled either individually or in combination with the targeting peptide. Our results offer a proof-of-concept for modifying synthetic nanogels with a combination of peptides that address barriers to cytosolic delivery individually and in tandem. Our data further motivate the need to identify endosome disrupting moieties which retain their activity within poly(acidic) networks.

Self-regulated hirudin delivery for anticoagulant therapy

Pathological coagulation, a disorder of blood clotting regulation, induces a number of cardiovascular diseases. A safe and efficient system for the delivery of anticoagulants to mimic the physiological negative feedback mechanism by responding to the coagulation signal changes holds the promise and potential for anticoagulant therapy. Here, we exploit a "closed-loop" controlled release strategy for the delivery of recombinant hirudin, an anticoagulant agent that uses a self-regulated nanoscale polymeric gel. The cross-linked nanogel network increases the stability and bioavailability of hirudin and reduces its clearance in vivo. Equipped with the clot-targeted ligand, the engineered nanogels promote the accumulation of hirudin in the fibrous clots and adaptively release the encapsulated hirudin upon the thrombin variation during the pathological proceeding of thrombus for potentiating anticoagulant activity and alleviating adverse effects. We show that this formulation efficiently prevents and inhibits the clot formation on the mouse models of pulmonary embolism and thrombosis.

Polymer Composition Primarily Determines the Protein Recognition Characteristics of Molecularly Imprinted Hydrogels

Synthetic hydrogels with the ability to recognize and bind target proteins are useful for a number of applications, including biosensing and therapeutic agent delivery. One popular method for fabricating recognitive hydrogels is molecular imprinting. A long-standing hypothesis of the field is that these molecularly imprinted polymers (MIPs) retain the chemical and geometric profile of their protein template, resulting in subsequent ability to recognize the template in solution. Here, we systematically determined the influence of network composition, as well as the identity, amount, and extraction of imprinting templates, on the protein binding of MIPs. Network composition (i.e. the relative number of ionizable and hydrophobic groups) explained the extent of protein adsorption in all cases. The identity and amount of imprinting template, albeit a protein or synthetic polymer (PEG) of similar molecular weight, did not significantly influence the amount of protein bound. While the purification method influenced the extent of template adsorption, it did so by chemically modifying the network (acrylamide hydrolysis, increasing the acid content by up to 21%) and not by voiding occupied MIP pores. Therefore, our results indicate that material composition determines the extent to which MIPs bind template and non-template proteins.

Gadofullerene inhibits the degradation of apolipoprotein B100 and boosts triglyceride transport for reversing hepatic steatosis

Hepatic steatosis is a widespread metabolic disease characterized by excessive accumulation of triglyceride (TG) in liver. So far, effective approved drugs for hepatic steatosis are still in development, and removing the unnecessary TG from the hepatocytes is an enormous challenge. Here, we explore a promising anti-hepatic steatosis strategy by boosting hepatocellular TG transport using β-alanine-modified gadofullerene (GF-Ala) nanoparticles. We confirm that GF-Ala could reverse hepatic steatosis in oleic acid-induced hepatocytes, fructose-induced mice, and obesity-associated transgenic ob/ob mice. Observably, GF-Ala improves hepatomegaly and hepatic lipid accumulation, reduces lipid peroxidation, and repairs abnormal mitochondria. Of note, we demonstrate that GF-Ala markedly inhibits the posttranslational degradation of apolipoprotein B100 (ApoB100) and boosts hepatocellular TG transport based on their superior antioxidant property. Together, we conclude that GF-Ala could potently ameliorate hepatic TG transport and maintain hepatic metabolic homeostasis without apparent toxicity, being beneficial for treatments of hepatic steatosis and other fatty liver diseases.

QCM-D assay for quantifying the swelling, biodegradation, and protein adsorption of intelligent nanogels

Environmentally responsive nanomaterials have been developed for drug delivery applications, in an effort to target and accumulate therapeutic agents at sites of disease. Within a biological system, these nanomaterials will experience diverse conditions which encompass a variety of solute identities and concentrations. In this study, we developed a new quartz crystal microbalance with dissipation (QCM-D) assay, which enabled the quantitative analysis of nanogel swelling, protein adsorption, and biodegradation in a single experiment. As a proof of concept, we employed this assay to characterize non-degradable and biodegradable poly(acrylamide-co-methacrylic acid) nanogels. We compared the QCM-D results to those obtained by dynamic light scattering to highlight the advantages and limitations of each method. We detailed our protocol development and practical recommendations, and hope that this study will serve as a guide for others to design application-specific QCM-D assays within the nanomedicine domain.

Hydrogels in the clinic

Injectable hydrogels are one of the most widely investigated and versatile technologies for drug delivery and tissue engineering applications. Hydrogels' versatility arises from their tunable structure, which has been enabled by considerable advances in fields such as materials engineering, polymer science, and chemistry. Advances in these fields continue to lead to invention of new polymers, new approaches to crosslink polymers, new strategies to fabricate hydrogels, and new applications arising from hydrogels for improving healthcare. Various hydrogel technologies have received regulatory approval for healthcare applications ranging from cancer treatment to aesthetic corrections to spinal fusion. Beyond these applications, hydrogels are being studied in clinical settings for tissue regeneration, incontinence, and other applications. Here, we analyze the current clinical landscape of injectable hydrogel technologies, including hydrogels that have been clinically approved or are currently being investigated in clinical settings. We summarize our analysis to highlight key clinical areas that hydrogels have found sustained success in and further discuss challenges that may limit their future clinical translation.

Optimization of Cationic Nanogel PEGylation to Achieve Mammalian Cytocompatibility with Limited Loss of Gram-Negative Bactericidal Activity

Tuning the composition of antimicrobial nanogels can significantly alter both nanogel cytotoxicity and antibacterial activity. This project investigated the extent to which PEGylation of cationic, hydrophobic nanogels altered their cytotoxicity and bactericidal activity. These biodegradable, cationic nanogels were synthesized by activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) emulsion polymerization with up to 13.9 wt % PEG (MW = 2000) MA, as verified by ¹H NMR. Nanogel bactericidal activity was assessed against Gram-negative E. coli and P. aeruginosa and Gram-positive S. mutans and S. aureus by measuring membrane lysis with a LIVE/DEAD assay. E. coli and S. mutans viability was further validated by measuring metabolic activity with a PrestoBlue assay and imaging bacteria stained with a LIVE/DEAD probe. All tested nanogels decreased the membrane integrity (0.5 mg/mL dose) for Gram-negative E. coli and P. aeruginosa, irrespective of the extent of PEGylation. PEGylation (13.9 wt %) increased the cytocompatibility of cationic nanogels toward RAW 264.7 murine macrophages and L929 murine fibroblasts by over 100-fold, relative to control nanogels. PEGylation (42.8 wt %) reduced nanogel uptake by 43% for macrophages and 63% for fibroblasts. Therefore, PEGylation reduced nanogel toxicity to mammalian cells without significantly compromising their bactericidal activity. These results facilitate future nanogel design for perturbing the growth of Gram-negative bacteria.

High-Efficiency Fluorescence through Bioinspired Supramolecular Self-Assembly

Peptide self-assembly has attracted extensive interest in the field of eco-friendly optoelectronics and bioimaging due to its inherent biocompatibility, intrinsic fluorescence, and flexible modulation. However, the practical application of such materials was hindered by the relatively low quantum yield of such assemblies. Here, inspired by the molecular structure of BFPms1, we explored the "self-assembly locking strategy" to design and manipulate the assembly of metal-stabilized cyclic(l-histidine-d-histidine) into peptide material with the high-fluorescence efficiency. We used this bioorganic material as an emissive layer in photo- and electroluminescent prototypes, demonstrating the feasibility of utilizing self-assembling peptides to fabricate a biointegrated microchip that incorporates eco-friendly and tailored optoelectronic properties. We further employed a "self-encapsulation" strategy for constructing an advanced nanocarrier with integrated in situ monitoring. The strategy of the supramolecular capture of functional components exemplifies the use of bioinspired organic chemistry to provide frontiers of smart materials, potentially allowing a better interface between sustainable optoelectronics and biomedical applications.

Molecular recognition with soft biomaterials

Biomacromolecules and engineered materials can achieve molecular recognition if they engage their ligand with properly oriented and chemically complementary moieties. Recently, there has been significant interest in fabricating recognitive soft materials, which possess specific affinity for biological analytes. We present a summary and evaluation of current recognitive materials for biosensing, drug delivery, and regenerative medicine applications. We highlight the impact of material composition on the extent and specificity of ligand adsorption, citing new theoretical and empirical evidence. We conclude with a guide for synthesizing and characterizing novel recognitive materials, as well as recommendations for ligand selection and experimental design.