We have witnessed a rapid growth in the field of a new nanoporous material group, metal organic frameworks (MOFs), over the past decade. MOFs possess a wide array of potential applications in chemical engineering, chemistry, and materials science, including gas storage, gas separation, and catalysis. One of the areas MOFs started to appear recently is biomedical applications. The unique physical and chemical characteristics of MOFs make them promising candidates for drug storage and drug delivery, nitric oxide storage and delivery, imaging, and sensing. In this review, we outline the recent progress of using MOFs as a promising platform in biomedical applications due to their high drug loading capacity, biodegradability, and versatile functionality. We also demonstrate the potential of MOFs for continuous development and implementation in biomedical applications by discussing issues including stability, toxicology, and biocompatibility. Although significant progress has been made in utilizing MOFs for biomedical applications, further improvements must still occur before MOFs can become viable therapeutics options.

Advances in design and fabrication of functional micro/nanomaterials have sparked growing interest in creating new mobile microswimmers for various healthcare applications, including local drug and other cargo ( e. g., gene, stem cell, and imaging agent) delivery. Such microswimmer-based cargo delivery is typically passive by diffusion of the cargo material from the swimmer body; however, controlled active release of the cargo material is essential for on-demand, precise, and effective delivery. Here, we propose a magnetically powered, double-helical microswimmer of 6 μm diameter and 20 μm length that can on-demand actively release a chemotherapeutic drug, doxorubicin, using an external light stimulus. We fabricate the microswimmers by two-photon-based 3D printing of a natural polymer derivative of chitosan in the form of a magnetic polymer nanocomposite. Amino groups presented on the microswimmers are modified with doxorubicin by means of a photocleavable linker. Chitosan imparts the microswimmers with biocompatibility and biodegradability for use in a biological setting. Controlled steerability of the microswimmers is shown under a 10 mT rotating magnetic field. With light induction at 365 nm wavelength and 3.4 × 10 W/cm intensity, 60% of doxorubicin is released from the microswimmers within 5 min. Drug release is ceased by controlled patterns of light induction, so as to adjust the desired release doses in the temporal domain. Under physiologically relevant conditions, substantial degradation of the microswimmers is shown in 204 h to nontoxic degradation products. This study presents the combination of light-triggered drug delivery with magnetically powered microswimmer mobility. This approach could be extended to similar systems where multiple control schemes are needed for on-demand medical tasks with high precision and efficiency.

We describe a new method that allows photopolymerization of hydrogels to occur on surfaces functionalized with eosin. In this work, glass and silicon surfaces were derivatized with eosin and photopolymerization was carried out using visible light (514 nm). This mild condition may have advantages over methods that use ultraviolet (UV) light (e.g., for encapsulation of cells and proteins, in drug screening, or in biosensing applications). The hydrogel formed on the modified surface is remarkably stable for an extended period of time. The resultant hydrogel was hydrated for more than 18 months without suffering delamination from the substrate surface. This strongly suggests covalent attachment of the hydrogel to the surface. Contact angle titration measurements and X-ray photoelectron spectroscopy analysis of eosin surfaces before and after irradiation in the presence of triethanolamine suggest that the eosin radical is responsible for the covalent attachment of the gel onto the substrate surface. This method allows for 2-D patterning of hydrogels, which is demonstrated here using the microcontact printing technique. However, noncontact photolithography could be used to form similar patterns by directing light through a mask. This method can be easily implemented to form arrays of fluorophores and proteins in situ.

Covalent attachment of polymers to cells and tissues could be used to solve a variety of problems associated with cellular therapies. Insulin-dependent diabetes mellitus is a disease resulting from the autoimmune destruction of the b cells of the islets of Langerhans in the pancreas. Transplantation of islets into diabetic patients is an attractive form of treatment, provided that the islets could be protected from the host's immune system to prevent graft rejection, and smaller numbers of islets transplanted in smaller volumes could be sufficient to reverse diabetes. Therefore, a need exists to develop islet encapsulation strategies that minimize transplant volume. In this study, we demonstrate the formation of nano-thin, poly(ethylene glycol) (PEG)-rich functional conformal coatings on individual islets via layer-by-layer assembly technique. The surface of the islets is modified with biotin-PEG-N-hydroxysuccinimide (NHS), and the islets are further covered by streptavidin (SA) and biotin-PEG-peptide conjugates using the layer-by-layer method. An insulinotropic ligand, glucagon-like peptide-1 (GLP-1), is conjugated to biotin-PEG-NHS. The insulinotropic effect of GLP-1 is investigated through layer-by-layer encapsulation of islets using the biotin-PEG-GLP-1 conjugate. The effect of islet surface modification using the biotin-PEG-GLP-1 conjugate on insulin secretion in response to glucose challenge is compared via static incubation and dynamic perifusion assays. The results show that islets coated with the functional PEG conjugate are capable of secreting more insulin in response to high glucose levels compared to control islets. Finally, the presence of SA is confirmed by indirect fluorescent staining with SA-Cy3, and the presence of PEGpeptide on the surface of the islets after treatment with biotin-PEG-GLP-1 is confirmed by indirect fluorescent staining with biotin-PEG-fluorescein isothiocyanate (FITC) and separately with an anti-GLP-1 antibody. This work demonstrates the feasibility of treating pancreatic islets with reactive polymeric segments and provides the foundation for a novel means of potential immunoisolation. With this technique, it may be possible to encapsulate and/or modify islets before portal vein transplantation and reduce transplantation volume significantly, and promote islet viability and insulin secretion due to the presence of insulinotropic peptides on the islet surface. Layer-by-layer self-assembly of PEG-GLP-1 offers a unique approach to islet encapsulation to stimulate insulin secretion in response to high glucose levels.

Biohybrid microswimmers exploit the swimming and navigation of a motile microorganism to target and deliver cargo molecules in a wide range of biomedical applications. Medical biohybrid microswimmers suffer from low manufacturing yields, which would significantly limit their potential applications. In the present study, a biohybrid design strategy is reported, where a thin and soft uniform coating layer is noncovalently assembled around a motile microorganism. Chlamydomonas reinhardtii (a single‐cell green alga) is used in the design as a biological model microorganism along with polymer–nanoparticle matrix as the synthetic component, reaching a manufacturing efficiency of ≈90%. Natural biopolymer chitosan is used as a binder to efficiently coat the cell wall of the microalgae with nanoparticles. The soft surface coating does not impair the viability and phototactic ability of the microalgae, and allows further engineering to accommodate biomedical cargo molecules. Furthermore, by conjugating the nanoparticles embedded in the thin coating with chemotherapeutic doxorubicin by a photocleavable linker, on‐demand delivery of drugs to tumor cells is reported as a proof‐of‐concept biomedical demonstration. The high‐throughput strategy can pave the way for the next‐generation generation microrobotic swarms for future medical active cargo delivery tasks.