Hooked on Cryogels: A Carbamate Linker Based Depot for Slow Drug Release

Redox-Responsive "Catch and Release" Cryogels: A Versatile Platform for Capture and Release of Proteins and Cells

Macroporous cryogels are attractive scaffolds for biomedical applications, such as biomolecular immobilization, diagnostic sensing, and tissue engineering. In this study, thiol-reactive redox-responsive cryogels with a porous structure are prepared using photopolymerization of a pyridyl disulfide poly(ethylene glycol) methacrylate (PDS-PEG-MA) monomer. Reactive cryogels are produced using PDS-PEG-MA and hydrophilic poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) monomers, along with a PEG-based cross-linker and photoinitiator. Functionalization of cryogels using a fluorescent dye via the disulfide-thiol exchange reactions is demonstrated, followed by release under reducing conditions. For ligand-mediated protein immobilization, first, thiol-containing biotin or mannose is conjugated onto the cryogels. Subsequently, fluorescent dye-labeled proteins streptavidin and concanavalin A (ConA) are immobilized via ligand-mediated conjugation. Furthermore, we demonstrate that the mannose-decorated cryogel could capture ConA selectively from a mixture of lectins. The efficiency of protein immobilization could be easily tuned by changing the ratio of the thiol-sensitive moiety in the scaffold. Finally, an integrin-binding cell adhesive peptide is attached to cryogels to achieve successful attachment, and the on-demand detachment of integrin-receptor-rich fibroblast cells is demonstrated. Redox-responsive cryogels can serve as potential scaffolds for a variety of biomedical applications because of their facile synthesis and modification.

Metal-Free Click-Chemistry: A Powerful Tool for Fabricating Hydrogels for Biomedical Applications

Increasing interest in the utilization of hydrogels in various areas of biomedical sciences ranging from biosensing and drug delivery to tissue engineering has necessitated the synthesis of these materials using efficient and benign chemical transformations. In this regard, the advent of "click" chemistry revolutionized the design of hydrogels and a range of efficient reactions was utilized to obtain hydrogels with increased control over their physicochemical properties. The ability to apply the "click" chemistry paradigm to both synthetic and natural polymers as hydrogel precursors further expanded the utility of this chemistry in network formation. In particular, the ability to integrate clickable handles at predetermined locations in polymeric components enables the formation of well-defined networks. Although, in the early years of "click" chemistry, the copper-catalyzed azide-alkyne cycloaddition was widely employed, recent years have focused on the use of metal-free "click" transformations, since residual metal impurities may interfere with or compromise the biological function of such materials. Furthermore, many of the non-metal-catalyzed "click" transformations enable the fabrication of injectable hydrogels, as well as the fabrication of microstructured gels using spatial and temporal control. This review article summarizes the recent advances in the fabrication of hydrogels using various metal-free "click" reactions and highlights the applications of thus obtained materials. One could envision that the use of these versatile metal-free "click" reactions would continue to revolutionize the design of functional hydrogels geared to address unmet needs in biomedical sciences.

Cryogels Based on Poly(2-oxazoline)s through Development of Bi- and Trifunctional Cross-Linkers Incorporating End Groups with Adjustable Stability

1,4-Bis(iodomethyl)benzene and 1,3,5-tris(iodomethyl)benzene were used as initiators for the cationic ring-opening polymerization (CROP) of 2-ethyl-2-oxazoline (EtOx) and its copolymerization with tert-butyl (3-(4,5-dihydrooxazol-2-yl)propyl)carbamate (BocOx) or methyl 3-(4,5-dihydrooxazol-2-yl)propanoate (MestOx). Kinetic studies confirmed the applicability of these initiators. Termination with suitable nucleophiles resulted in two- and three-armed cross-linkers featuring acrylate, methacrylate, piperazine-acrylamide, and piperazine-methacrylamide as polymerizable ω-end groups. Matrix-assisted laser desorption/ionization mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy confirmed the successful attachment of the respective ω-end groups at all initiation sites for every prepared cross-linkers. Except for acrylate, each ω-end group remained stable during deprotection of BocOx containing cross-linkers. The cryogels were prepared using EtOx-based cross-linkers, as confirmed by solid-state NMR spectroscopy, scanning electron microscopy, and thermogravimetric analysis. Stability tests revealed a complete dissolution of the acrylate-containing gels at pH = 14, whereas the piperazine-acrylamide-based cryogels featured excellent hydrolytic stability.

Package delivered: folate receptor-mediated transporters in cancer therapy and diagnosis

Neoplasias pose a significant threat to aging society, underscoring the urgent need to overcome the limitations of traditional chemotherapy through pioneering strategies. Targeted drug delivery is an evolving frontier in cancer therapy, aiming to enhance treatment efficacy while mitigating undesirable side effects. One promising avenue utilizes cell membrane receptors like the folate receptor to guide drug transporters precisely to malignant cells. Based on the cellular folate receptor as a cancer cell hallmark, targeted nanocarriers and small molecule-drug conjugates have been developed that comprise different (bio) chemistries and/or mechanical properties with individual advantages and challenges. Such modern folic acid-conjugated stimuli-responsive drug transporters provide systemic drug delivery and controlled release, enabling reduced dosages, circumvention of drug resistance, and diminished adverse effects. Since the drug transporters' structure-based de novo design is increasingly relevant for precision cancer remediation and diagnosis, this review seeks to collect and debate the recent approaches to deliver therapeutics or diagnostics based on folic acid conjugated Trojan Horses and to facilitate the understanding of the relevant chemistry and biochemical pathways. Focusing exemplarily on brain and breast cancer, recent advances spanning 2017 to 2023 in conjugated nanocarriers and small molecule drug conjugates were considered, evaluating the chemical and biological aspects in order to improve accessibility to the field and to bridge chemical and biomedical points of view ultimately guiding future research in FR-targeted cancer therapy and diagnosis.

Super-Macroporous Pulluan Cryogels as Controlled Active Delivery Systems with Controlled Degradability

Here, super-macroporous cryogel from a natural polysaccharide, pullulan was synthesized using a cryo-crosslinking technique with divinyl sulfone (DVS) as a crosslinker. The hydrolytic degradation of the pullulan cryogel in various simulated body fluids (pH 1.0, 7.4, and 9.0 buffer solutions) was evaluated. It was observed that the pullulan cryogel degradation was much faster in the pH 9 buffer solution than the pH 1.0 and 7.4 buffer solutions in the same time period. The weight loss of the pullulan cryogel at pH 9.0 within 28 days was determined as 31% ± 2%. To demonstrate the controllable drug delivery potential of pullulan cryogels via degradation, an antibiotic, ciprofloxacin, was loaded into pullulan cryogels (pullulan-cipro), and the loading amount of drug was calculated as 105.40 ± 2.6 µg/mg. The release of ciprofloxacin from the pullulan-cipro cryogel was investigated in vitro at 37.5 °C in physiological conditions (pH 7.4). The amount of drug released within 24 h was determined as 39.26 ± 3.78 µg/mg, which is equal to 41.38% ± 3.58% of the loaded drug. Only 0.1 mg of pullulan-cipro cryogel was found to inhibit half of the growing Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) colonies for 10 min and totally eradicated within 2 h by the release of the loaded antibiotic. No significant toxicity was determined on L929 fibroblast cells for 0.1 mg drug-loaded pullulan cryogel. In contrast, even 1 mg of drug-loaded pullulan cryogel revealed slight toxicity (e.g., 66% ± 9% cell viability) because of the high concentration of released drug.

Cryogels: Advancing Biomaterials for Transformative Biomedical Applications

Cryogels, composed of synthetic and natural materials, have emerged as versatile biomaterials with applications in tissue engineering, controlled drug delivery, regenerative medicine, and therapeutics. However, optimizing cryogel properties, such as mechanical strength and release profiles, remains challenging. To advance the field, researchers are exploring advanced manufacturing techniques, biomimetic design, and addressing long-term stability. Combination therapies and drug delivery systems using cryogels show promise. In vivo evaluation and clinical trials are crucial for safety and efficacy. Overcoming practical challenges, including scalability, structural integrity, mass transfer constraints, biocompatibility, seamless integration, and cost-effectiveness, is essential. By addressing these challenges, cryogels can transform biomedical applications with innovative biomaterials.

Biomimetic, Injectable, and Self-Healing Hydrogels with Sustained Release of Ranibizumab to Treat Retinal Neovascularization

Retinal neovascularization (RNV) is a typical feature of ischemic retinal diseases that can lead to traction retinal detachment and even blindness in patients, in which the vascular endothelial cell growth factor (VEGF) plays a pivotal role. However, most anti-VEGF drugs currently used for treating RNV, such as ranibizumab, need frequent and repeated intravitreal injections due to their short intravitreal half-life, which increases the incidence of complications. Herein, a hydrogel intravitreal drug delivery system (DDS) is prepared by a dynamic Schiff base reaction between aminated hyaluronic acid and aldehyde-functionalized Pluronic 127 for sustained release of ranibizumab. The prepared hydrogel system named HP@Ran exhibits excellent injectability, self-healing ability, structural stability, cytocompatibility, and blood compatibility. According to an in vitro drug release study, the hydrogel system continuously releases the model drug bovine serum albumin for more than 56 days. Importantly, in an in vivo rabbit persistent RNV model, the HP@Ran hydrogel system continuously releases pharmacologically active ranibizumab for more than 7 weeks and also exhibits superior anti-angiogenic efficacy over ranibizumab treatment by decreasing vascular leakage and neovascularization at 12 weeks. Thus, the developed HP@Ran hydrogel system possesses great potential for intravitreal DDS for the treatment of RNV.

pH-Responsive nanofiber buttresses as local drug delivery devices

Electrospun nanofibers are a 3D scaffold of choice for many drug delivery devices due to their high surface area, significant capacity for drug payload, ease of in situ placement, and scalable manufacture. Herein, we report the synthesis of polymeric, pH-responsive nanofiber buttresses via electrospinning. The homopolymer is comprised of an acrylic backbone with acid-sensitive, hydrolyzable, trimethoxybenzaldehyde-protected side chains that lead to buttress transformation from a hydrophobic to a hydrophilic state under physiologically relevant pH conditions (e.g., extracellular tumor environment with pH = 6.5). Hydrolysis of the side chains leads to an increase in fiber diameter from approximately 350 to 900 nm and the release of the encapsulated drug cargo. In vitro drug release profiles demonstrate that significantly more drug is released at pH 5.5 compared to pH 7.4, thereby limiting the release to the target site, with docetaxel releasing over 20 days and doxorubicin over 7 days. Drug burst release, defined as >50% within 24 hours, does not occur at either pH or with either drug. Drug-loaded buttresses preserve drug activity and are cytotoxic to multiple human cancer lines, including breast and lung. Important to their potential application in surgical applications, the tensile strength of the buttresses is 6.3 kPa and, though weaker than commercially available buttresses, they provide sufficient flexibility and mechanical integrity to serve as buttressing materials via the application with a conventional surgical cutting stapler.

Investigation of the Impact of Hydrolytically Cleavable Groups on the Stability of Poly(ethylene glycol) Based Hydrogels Cross-Linked via the Inverse Electron Demand Diels-Alder (iEDDA) Reaction

Eight-armed poly(ethylene glycol) (PEG) hydrogels cross-linked via inverse electron demand Diels-Alder reaction between norbornene and tetrazine groups are promising materials for long-term protein delivery. While a controlled release over 265 days is achieved for 15% w/v hydrogels in the previous study, the material shows high stability over 500 days despite having cleavable ester linkages between the PEG macromonomers and their functionalities. In this study, the hydrolyzable ester linkers in the PEG-norbornene precursor structure are exchanged to reduce the degradation time. To this end, 3,6-epoxy-1,2,3,6-tetrahydrophthalimide, phenyl carbamate, carbonate ester, and phenyl carbonate ester are introduced as degradable functional groups. Oscillatory shear experiments reveal that they are not affected the in situ gelation. All hydrogel types have gel points of less than 20 s even at a low polymer concentration of 5% w/v. Hydrogels with varying polymer concentrations have similar mesh sizes, all of which fell in the range of 4-12 nm. The inclusion of phenyl carbonate ester accelerates degradation considerably, with complete dissolution of 15% w/v hydrogels after 302 days of incubation in phosphate buffer (pH 7.4). Controlled release of 150 kDa fluorescein isothiocyanate-dextran over a period of at least 150 days is achieved with 15% w/v hydrogels.

Regulation of drug release performance using mixed doxorubicin-doxorubicin dimer nanoparticles as a pH-triggered drug self-delivery system

A mixed drug self-delivery system (DSDS) with high drug content (>50%) was developed to regulate pH-triggered drug release, based on two doxorubicin (DOX)-DOX dimmers: D-DOXADH and D-DOXcar conjugated with acid-labile dynamic covalent bonds (hydrazone and carbamate, respectively) and stabilized with PEGylated D-DOXADH (D-DOXADH-PEG). Owing to the different stability of the dynamic covalent bonds in the two dimers and the noncovalent interaction between them, pH-triggered drug release could be easily regulated by adjusting the feeding ratios of the two DOX-DOX dimers in the mixed DSDS. Similar in vitro cellular toxicity was achieved with the mixed DSDS nanoparticles prepared with different feeding ratios. The mixed DSDS nanoparticles had a similar DOX content and diameter but different drug releasing rates. The MTT assays revealed that a high anti-tumor efficacy could be achieved with the slow-release mixed DSDS nanoparticles.

Molecular bottlebrush with pH-responsive cleavable bonds as a unimolecular vehicle for anticancer drug delivery

Drug delivery systems with targeted and smart properties have emerged as an efficient strategy to overcome the challenges of cancer chemotherapy such as toxic side effects and the development of multidrug resistance. In this study, a biocompatible bottlebrush polymer poly((3-(2-bromo-2-methylpropionate)propyldimethylsilyloxy)ethyl methacrylate)-graft-poly(2-methacryloyloxyethyl phosphorylcholine) P(BIBS-EMA)-g-PMPC with pH-responsive silanol cleavable bond was designed and developed for delivery of doxorubicin. A549 cell line of human lung carcinoma was tested. The synthesized bottlebrush polymer was analyzed and characterized via Fourier transform infrared spectroscopy, FTIR, nuclear magnetic resonance spectroscopy, ¹H NMR, gel permeation chromatography, GPC, dynamic laser light scattering, DLS, and static laser light scattering, SLS, techniques. The cleavage process was also precisely studied to confirm the pH-responsiveness of such bottlebrush polymers. In vitro loading and release studies of doxorubicin as a model drug were examined and the results showed a pH-dependent release manner with a twice higher release rate under cancerous tissue conditions compared to standard physiological conditions. MTT cytotoxicity assay was also performed to prove the biocompatibility of the designed polymeric platform on healthy human cells. Due to the presence of bio-inspired poly(2-methacryloyloxyethyl phosphorylcholine) side chains in the prepared bottlebrush polymer, the formed polymer-drug complex could also exhibit effective internalization into tumor cells. These facts further support the potential use of this carrier in drug delivery applications and for further in vivo studies.

Photothermally Active Cryogel Devices for Effective Release of Antimicrobial Peptides: On-Demand Treatment of Infections

There has been significant interest in the use of peptides as antimicrobial agents, and peptide containing hydrogels have been proposed as biological scaffolds for various applications. Limited stability and rapid clearance of small molecular weight peptides pose challenges to their widespread implementation. As a common approach, antibacterial peptides are physically loaded into hydrogel scaffolds, which leads to continuous release through the passive mode with spatial control but provides limited control over drug dosage. Although utilization of peptide covalent linkage onto hydrogels addresses partially this problem, the peptide release is commonly too slow. To alleviate these challenges, in this work, maleimide-modified antimicrobial peptides are covalently conjugated onto furan-based cryogel (CG) scaffolds via the Diels-Alder cycloaddition at room temperature. The furan group offers a handle for specific loading of the peptides, thus minimizing passive and burst drug release. The porous nature of the CG matrix provides rapid loading and release of therapeutic peptides, apart from high water uptake. Interfacing the peptide adduct containing a CG matrix with a reduced graphene oxide-modified Kapton substrate allows "on-demand" photothermal heating upon near-infrared (NIR) irradiation. A fabricated photothermal device enables tunable and efficient peptide release through NIR exposure to kill bacteria. Apart from spatial confinement offered by this CG-based bandage, the selective ablation of planktonic Staphylococcus aureus is demonstrated. It can be envisioned that this modular "on-demand" peptide-releasing device can be also employed for other topical applications by appropriate choice of therapeutic peptides.

High-Fidelity End-Functionalization of Poly(ethylene glycol) Using Stable and Potent Carbamate Linkages

Commercial PEG-amine is of unreliable quality, and conventional PEG functionalization relies on esterification and etherification steps, suffering from incomplete conversion, harsh reaction conditions, and functional-group incompatibility. To solve these challenges, we propose an efficient strategy for PEG functionalization with carbamate linkages. By fine-tuning terminal amine basicity, stable and high-fidelity PEG-amine with carbamate linkage was obtained, as seen from the clean MALDI-TOF MS pattern. The carbamate strategy was further applied to the synthesis of high-fidelity multi-functionalized PEG with varying reactive groups. Compared to with an ester linkage, amphiphilic PEG-PS block copolymers bearing carbamate junction linkage exhibits preferential self-assembly tendency into vesicles. Moreover, nanoparticles of the latter demonstrate higher drug loading efficiency, encapsulation stability against enzymatic hydrolysis, and improved in vivo retention at the tumor region.

An 'on-demand' photothermal antibiotic release cryogel patch: evaluation of efficacy on an ex vivo model for skin wound infection

A myriad of topical therapies and dressings are available to the clinicians for wound healing skin, but only a very few have shown their effectiveness in promoting wound repair due to challenges in controlling drug release. To address this issue, in this work, a near infrared (NIR)-light activable cryogel based on butyl methacrylate (BuMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) incorporated with reduced graphene oxide (rGO) was fabricated. The obtained cryogel provides the required hydrophilicity beneficial for wound treatment. The excellent photo-thermal properties of rGO allow for heating the cryogel, which results in subsequent swelling of the cryogel (CG) followed by release of the encapsulated drug load, cefepime in our case. Without photothermal activation, no release of payload was observed. The potential of this bandage for wound healing was examined using an ex vivo human skin model infected with Staphylococcus aureus (S. aureus). Apart from the efficacy of the cryogel based wound healing system, our results also suggest that the ex vivo wound model evaluated here provides a rapid and valuable tool to study superficial skin infections in humans and test the efficacy of antimicrobial agents.

Thiol-Reactive Clickable Cryogels: Importance of Macroporosity and Linkers on Biomolecular Immobilization

Macroporous cryogels that are amenable to facile functionalization are attractive platforms for biomolecular immobilization, a vital step for fabrication of scaffolds necessary for areas like tissue engineering and diagnostic sensing. In this work, thiol-reactive porous cryogels are obtained via photopolymerization of a furan-protected maleimide-containing poly(ethylene glycol) (PEG)-based methacrylate (PEGFuMaMA) monomer. A series of cryogels are prepared using varying amounts of the masked hydrophilic PEGFuMaMA monomer, along with poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) dimethacrylate, a hydrophilic monomer and cross-linker, respectively, in the presence of a photoinitiator. Subsequent activation to the thiol-reactive form of the furan-protected maleimide groups is performed through the retro Diels-Alder reaction. As a demonstration of direct protein immobilization, bovine serum albumin is immobilized onto the cryogels. Furthermore, ligand-directed immobilization of proteins is achieved by first attaching mannose- or biotin-thiol onto the maleimide-containing platforms, followed by ligand-directed immobilization of concanavalin A or streptavidin, respectively. Additionally, we demonstrate that the extent of immobilized proteins can be controlled by varying the amount of thiol-reactive maleimide groups present in the cryogel matrix. Compared to traditional hydrogels, cryogels demonstrate enhanced protein immobilization/detection. Additionally, it is concluded that utilization of a longer linker, distancing the thiol-reactive maleimide group from the gel scaffold, considerably increases protein immobilization. It can be envisioned that the facile fabrication, conjugation, and control over the extent of functionalization of these cryogels will make these materials desirable scaffolds for numerous biomedical applications.

Synthetic routes to nanoconjugates of anthracyclines

Anthracyclines (Anth) are widely used in the treatment of various types of cancer. Unfortunately, they exhibit serious adverse effects, such as hematopoietic depression and cardiotoxicity, leading to heart failure. In this review, we focus on recently developed conjugates of anthracyclines with a range of nanocarriers, such as polymers, peptides, DNA or inorganic systems. Manipulation of the composition, size and shape of chemical entities at the nanometer scale makes possible the design and development of a range of prodrugs. In this review we concentrate on synthetic chemistry in the long process leading to the introduction of novel therapeutic products.

Pyridyl disulfide-based thiol–disulfide exchange reaction: shaping the design of redox-responsive polymeric materials

This review provides an overview of synthetic approaches utilized to incorporate the thiol-reactive pyridyl-disulfide motif into various polymeric materials, and briefly highlights its utilization to obtain functional materials.

A modular and orthogonally reactive platform for fabrication of polymer–drug conjugates for targeted delivery

Increasing interest in utilization of polymeric systems in targeted drug delivery has necessitated fabrication of polymers that undergo facile functionalization with targeting groups and therapeutic agents in a modular and orthogonal fashion.

Doxorubicin-doxorubicin conjugate prodrug as drug self-delivery system for intracellular pH-triggered slow release

Drug content and releasing rate are the main determining factors for the drug delivery systems (DDSs). Here, doxorubicin dimer (D-DOXcar) was synthesized as drug-drug conjugate prodrug with high drug content of 86%, via an acid-triggered hydrolysable carbamate linker. The prodrug nanoparticles (D-DOXcar-NP) with different diameters were prepared as drug self-delivery system (DSDS) for intracellular pH-triggered slow release. They showed size- and concentration-dependent pH-triggered slow DOX release. For the D-DOXcar-sNP with smaller diameter, the cumulative release ratio reached 25.6% at pH 5.0 within 60 h. The MTT results demonstrated that the proposed DSDS showed similar tumor inhibition regardless of carboxylesterases, and an enhanced anti-tumor efficacy on the HepG2 cells in comparison with the free DOX.

pH-Labile Magnetic Nanocarriers for Intracellular Drug Delivery to Tumor Cells

We report the development of pH-labile ascorbic acid-coated magnetic nanocarriers (AMNCs) for effective delivery of the anticancer drug doxorubicin hydrochloride (DOX) to tumor cells. The uniqueness of this drug delivery system lies in the covalent conjugation of DOX through carbamate and hydrazone bonds, resulting in a slow and sustained drug release profile at different environmental acidities. X-ray diffraction and transmission electron microscopy analyses reveal the formation of crystalline single-phase Fe₃O₄ nanoparticles with an average size of 10 nm. The changes in the interfacial characteristics of the nanocarriers and the presence of organic coatings are probed by infrared spectroscopy, dynamic light scattering, zeta potential, and thermogravimetric measurements. AMNCs show high colloidal stability in aqueous and cell culture media and possess good magnetic field responsivity and protein resistance characteristics. The drug-loaded nanocarriers exhibited sustained pH-triggered release of drug molecules in acidic mediums, substantial cellular internalization, and significant toxicity toward the proliferation of mouse skin fibrosarcoma (WEHI-164), human breast cancer (MCF-7), and human lung cancer (A549) cells. However, it showed significantly lower toxicity in human normal lung (WI26VA) cells. Overall, these results suggest a pH-sensitive drug release of nanoformulations, which showed selective toxicity to tumor than normal cells.

Design and synthesis of a dual imageable theranostic platinum prodrug for efficient cancer therapy

Platinum-based chemotherapeutic agents are considered first-line treatments for various cancers but their application is limited by the lack of site specificity and severe side effects.

In Situ Drug Delivery to Breast Cancer-Associated Extracellular Matrix

The extracellular matrix (ECM) contributes to tumor progression through changes induced by tumor and stromal cell signals that promote increased ECM density and stiffness. The increase in ECM stiffness is known to promote tumor cell invasion into surrounding tissues and metastasis. In addition, this scar-like ECM creates a protective barrier around the tumor that reduces the effectiveness of innate and synthetic antitumor agents. Herein, clinically approved breast cancer therapies as well as novel experimental approaches that target the ECM are discussed, including in situ hydrogel drug delivery systems, an emerging technology the delivers toxic chemotherapeutics, gene-silencing microRNAs, and tumor suppressing immune cells directly inside the tumor. Intratumor delivery of therapeutic agents has the potential to drastically reduce systemic side effects experienced by the patient and increase the efficacy of these agents. This review also describes the opposing effects of ECM degradation on tumor progression, where some studies report improved drug delivery and delayed cancer progression and others report enhanced metastasis and decreased patient survival. Given the recent increase in ECM-targeting drugs entering preclinical and clinical trials, understanding and addressing the factors that impact the effect of the ECM on tumor progression is imperative for the sake of patient safety and survival outcome.