Sequential pore wall functionalization in covalent organic frameworks and application to stable camptothecin delivery systems

Covalent organic frameworks (COFs) as carrier for improved drug delivery and biosensing applications

Porous organic frameworks (POFs) represent a significant subclass of nanoporous materials in the field of materials science, offering exceptional characteristics for advanced applications. Covalent organic frameworks (COFs), as a novel and intriguing type of porous material, have garnered considerable attention due to their unique design capabilities, diverse nature, and wide-ranging applications. The unique structural features of COFs, such as high surface area, tuneable pore size, and chemical stability, render them highly attractive for various applications, including targeted and controlled drug release, as well as improving the sensitivity and selectivity of electrochemical biosensors. Therefore, it is crucial to comprehend the methods employed in creating COFs with specific properties that can be effectively utilized in biomedical applications. To address this indispensable fact, this review paper commences with a concise summary of the different methods and classifications utilized in synthesizing COFs. Second, it highlights the recent advancements in COFs for drug delivery, including drug carriers as well as the classification of drug delivery systems and biosensing, encompassing drugs, biomacromolecules, small biomolecules and the detection of biomarkers. While exploring the potential of COFs in the biomedical field, it is important to acknowledge the limitations that researchers may encounter, which could impact the practicality of their applications. Third, this paper concludes with a thought-provoking discussion that thoroughly addresses the challenges and opportunities associated with leveraging COFs for biomedical applications. This review paper aims to contribute to the scientific community's understanding of the immense potential of COFs in improving drug delivery systems and enhancing the performance of biosensors in biomedical applications.

Phospholipid-inspired alkoxylation induces crystallization and cellular uptake of luminescent COF nanocarriers

The porous nature and structural variability of covalent organic frameworks (COFs) make them preferred for drug loading and delivery applications. However, most COF materials suffer from poor luminescent properties and inefficiency for cell uptake. Herein, we experimentally demonstrate the crucial role of long alkoxy chains in the synthesis of crystalline COF nanostructures with high cellular uptake efficiency. After luminescence integration through band engineering, the semiconducting COF exhibits an optical bandgap of 2.05 eV, an emission wavelength of 632 nm, a high quantum yield of 37 %, and excellent fluorescence stability (100 % at 3 h). Such excellent optical properties of the designed COF nanocarriers enable quantitative evaluations of cellular uptake and visual tracking of drug delivery. It was demonstrated that the cellular uptake efficiency was enhanced by orders of magnitude for the COF after the introduction of long n-octyloxy chains, which firstly delivered the anticancer camptothecin (CPT) to cell lysosomes, and then underwent "endo/lysosomal escape" to induce cell apoptosis. In vivo assay evidenced a significant enhancement in the therapeutic effect with a 96 % inhibition of tumor growth after 14 days of treatment. This progress sheds light on designing cutting-edge drug delivery nanosystems based on COF materials with integrated diagnostic and therapeutic functions.

Covalent Organic Frameworks: Opportunities for Rational Materials Design in Cancer Therapy

Nanomedicines are extensively used in cancer therapy. Covalent organic frameworks (COFs) are crystalline organic porous materials with several benefits for cancer therapy, including porosity, design flexibility, functionalizability, and biocompatibility. This review examines the use of COFs in cancer therapy from the perspective of reticular chemistry and function-oriented materials design. First, the modification sites and functionalization methods of COFs are discussed, followed by their potential as multifunctional nanoplatforms for tumor targeting, imaging, and therapy by integrating functional components. Finally, some challenges in the clinical translation of COFs are presented with the hope of promoting the development of COF-based anticancer nanomedicines and bringing COFs closer to clinical trials.

Red-Fluorescent Covalent Organic Framework Nanospheres for Trackable Anticancer Drug Delivery

Covalent organic frameworks (COFs) have emerged as promising drug carriers due to their structural variability, inherent porosity, and customizable functions. However, most COFs used in drug delivery suffer from low cellular bioavailability and poor luminescence properties. In this study, we designed a series of size-tunable, crystalline, and red-fluorescent COF nanospheres (COFNSs) for trackable anticancer drug delivery. The semiconducting COFNSs were prepared by condensations of 1,3,5-triformylbenzene (TFB) with various dihydrazide blocks through the Schiff-base reaction, resulting in red emission at 647 nm and excellent fluorescence stability (∼100% for 1 h). Such fluorescence property allowed for systematic investigation of the cellular endocytosis pathway of COFNSs, visualization of drug delivery, and observation of the cell apoptosis process. The COFNSs exhibited high cell viability (>90%), a loading capacity of 183 wt % for the anticancer drug camptothecin (CPT), and significant enhancement in inhibiting 4T1 cancers both in vitro and in vivo as the CPT nanocarrier. This progress presents a valuable approach to design COF nanocarriers with integrated fluorescent and drug delivery functions.

Drug delivery using biocompatible covalent organic frameworks (COFs) towards a therapeutic approach

Covalent organic frameworks (COFs) are constructed exclusively with lightweight organic scaffolds, which can have a 2D or 3D architecture. The ease of synthesis, robust skeleton and tunable properties of COFs make them superior candidates among their counterparts for a wide range of uses including biomedical applications. In the biomedical field, drug delivery or photodynamic-photothermal (PDT-PTT) therapy can be individually considered a potential parameter to be investigated. Therefore, this comprehensive review is focused on drug delivery using COFs, highlighting the encapsulation and decapsulation of drugs by COF scaffolds and their delivery in biological media including live cells. Versatile COF scaffolds together with the delivery of several drug molecules are considered. We attempted to incorporate the status of drug encapsulation and decapsulation considering a wide range of recent publications.

Development of the new pH-driven carrier from alginate/carboxymethyl starch bio-coated co-drugs@COF-OH for controlled and concomitant colon cancer treatment

To develop a new more efficient colon cancer treatment bio-vehicle, in frontier research, for the first time, an attempt has been made to design a unique colon-targeted bio-carrier containing polysaccharides along with nanoporous materials. So, at first, an imine-based covalent organic framework (COF-OH) with respectively an average pore diameter and surface area at 8.5058 nm and 208.29 m²·g^-1 was fabricated. In the next step, about 41.68 % and 95.8 % of 5-fluorouracil (5-Fu) and curcumin (CUR) respectively were loaded on COF-OH, and 5-Fu + CUR@COF-OH was achieved. Due to the higher rate of drug releases in simulated stomach media, 5-Fu + CUR@COF-OH was coated with a mixture of alginate (Alg) and carboxymethyl starch (CMS) via the ionic crosslinking (Alg/CMS@(5-Fu + CUR@COF-OH)). Findings displayed that the use of polysaccharide coat reduce the drug releases in simulated gastric and improved it in simulated intestinal and colonic fluids. The beads swelled about 93.33 % under simulated gastrointestinal conditions, but this value was found higher in the simulated colonic environment and reached 326.67 %. The hemolysis rate lower than 5 %, as well as the cell viability higher than 80 %, were the main showing signs of system biocompatibility. Altogether, the results of the preliminary investigations can highlight the potential of the Alg/CMS@(5-Fu + CUR@COF-OH) for colon-specific drug delivery.

Silica-Based Stimuli-Responsive Systems for Antitumor Drug Delivery and Controlled Release

The administration of cytotoxic drugs in classical chemotherapy is frequently limited by water solubility, low plasmatic stability, and a myriad of secondary effects associated with their diffusion to healthy tissue. In this sense, novel pharmaceutical forms able to deliver selectively these drugs to the malign cells, and imposing a space-time precise control of their discharge, are needed. In the last two decades, silica nanoparticles have been proposed as safe vehicles for antitumor molecules due to their stability in physiological medium, high surface area and easy functionalization, and good biocompatibility. In this review, we focus on silica-based nanomedicines provided with specific mechanisms for intracellular drug release. According to silica nature (amorphous, mesostructured, and hybrids) nanocarriers responding to a variety of stimuli endogenously (e.g., pH, redox potential, and enzyme activity) or exogenously (e.g., magnetic field, light, temperature, and ultrasound) are proposed. Furthermore, the incorporation of targeting molecules (e.g., monoclonal antibodies) that interact with specific cell membrane receptors allows a selective delivery to cancer cells to be carried out. Eventually, we present some remarks on the most important formulations in the pipeline for clinical approval, and we discuss the most difficult tasks to tackle in the near future, in order to extend the use of these nanomedicines to real patients.

Two-dimensional biomaterials: material science, biological effect and biomedical engineering applications

To date, nanotechnology has increasingly been identified as a promising and efficient means to address a number of challenges associated with public health. In the past decade, two-dimensional (2D) biomaterials, as a unique nanoplatform with planar topology, have attracted explosive interest in various fields such as biomedicine due to their unique morphology, physicochemical properties and biological effect. Motivated by the progress of graphene in biomedicine, dozens of types of ultrathin 2D biomaterials have found versatile bio-applications, including biosensing, biomedical imaging, delivery of therapeutic agents, cancer theranostics, tissue engineering, as well as others. The effective utilization of 2D biomaterials stems from the in-depth knowledge of structure-property-bioactivity-biosafety-application-performance relationships. A comprehensive summary of 2D biomaterials for biomedicine is still lacking. In this comprehensive review, we aim to concentrate on the state-of-the-art 2D biomaterials with a particular focus on their versatile biomedical applications. In particular, we discuss the design, fabrication and functionalization of 2D biomaterials used for diverse biomedical applications based on the up-to-date progress. Furthermore, the interactions between 2D biomaterials and biological systems on the spatial-temporal scale are highlighted, which will deepen the understanding of the underlying action mechanism of 2D biomaterials aiding their design with improved functionalities. Finally, taking the bench-to-bedside as a focus, we conclude this review by proposing the current crucial issues/challenges and presenting the future development directions to advance the clinical translation of these emerging 2D biomaterials.

Covalent Organic Frameworks: Synthesis, Properties and Applications-An Overview

Covalent Organic Frameworks (COFs) are an exciting new class of microporous polymers with unprecedented properties in organic material chemistry. They are generally built from rigid, geometrically defined organic building blocks resulting in robust, covalently bonded crystalline networks that extend in two or three dimensions. By strategically combining monomers with specific structures and properties, synthesized COF materials can be fine-tuned and controlled at the atomic level, with unparalleled precision on intrapore chemical environment; moreover, the unusually high pore accessibility allows for easy post-synthetic pore wall modification after the COF is synthesized. Overall, COFs combine high, permanent porosity and surface area with high thermal and chemical stability, crystallinity and customizability, making them ideal candidates for a myriad of promising new solutions in a vast number of scientific fields, with widely varying applications such as gas adsorption and storage, pollutant removal, degradation and separation, advanced filtration, heterogeneous catalysis, chemical sensing, biomedical applications, energy storage and production and a vast array of optoelectronic solutions. This review attempts to give a brief insight on COF history, the overall strategies and techniques for rational COF synthesis and post-synthetic functionalization, as well as a glance at the exponentially growing field of COF research, summarizing their main properties and introducing the numerous technological and industrial state of the art applications, with noteworthy examples found in the literature.