Layer-by-layer films for biomedical applications

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Multi-Layered Hydrogels for Biomedical Applications

Large films will often tear when lifted out of the water, and in some cases they tear while drying. Biomedical membranes today are manufactured through such processes as microlithography, ion beam etching, electrochemical leaching anodization and sol-gel processes. PEEL offers a potentially simpler, faster way to produce biomedically useful membranes. PEEL was originally developed to produce ultrathin films for the assembly of inertial confinement fusion targets.

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These targets have a fuel capsule that must be supported with minimal mass to avoid perturbations to the implosion. PEEL employs robust, water-based, and self-optimizing surface chemistry to fabricate ultrathin films greater than cm2 in area. The process is easily scalable in size and manufacturing quantity and applicable to a variety of polymeric materials.

The flexibility of PEEL is the key to its usefulness to industrial processes. It is scalable up to roll-to-roll level for high manufacturing volumes.

Lipid-based Films for Biomedical Applications [Video]

It can use any kind of chemistry to generate membranes. This makes PEEL a far more environmentally benign, safer process. PEEL allows its user to self-optimize the manufacturing process at any scale from surface micromachining to roll level. The scalability, low cost, and environmentally benign chemistry of PEEL offer benefits to a wide range of membrane manufacturing processes in use today. It could help manufacturers overcome a cost and production barriers limiting the broader adoption of advanced membrane technologies that are thought too costly or too difficult to manufacture.

Membranes for biomedical uses are experiencing a surge of interest. Biocompatible membranes have applications ranging from hemodialysis to wound dressing, purifying biologically active materials, drug delivery through implantable devices with nanoporous membranes, and manufacturing artificial tissues such as blood vessels and cartilage for medical purposes. Global reach, higher impact. Theranostics ; 8 4 Black phosphorus BP , also known as phosphorene, has attracted recent scientific attention since its first successful exfoliation in owing to its unique structure and properties.

In particular, its exceptional attributes, such as the excellent optical and mechanical properties, electrical conductivity and electron-transfer capacity, contribute to its increasing demand as an alternative to graphene-based materials in biomedical applications. Although the outlook of this material seems promising, its practical applications are still highly challenging. In this review article, we discuss the unique properties of BP, which make it a potential platform for biomedical applications compared to other 2D materials, including graphene, molybdenum disulphide MoS 2 , tungsten diselenide WSe 2 and hexagonal boron nitride h-BN.

We then introduce various synthesis methods of BP and review its latest progress in biomedical applications, such as biosensing, drug delivery, photoacoustic imaging and cancer therapies i. Lastly, the existing challenges and future perspective of BP in biomedical applications are briefly discussed.

Keywords : black phosphorus, biosensing, drug delivery, photoacoustic imaging, photothermal and photodynamic therapies. Two-dimensional 2D materials, particularly graphene and its derivative graphene oxide GO , are increasingly gaining scientific interest due to their excellent mechanical properties and electrical conductivity, large surface area-to-volume ratio and easy functionalization [ 1 , 2 ]. Similarly, inorganic graphene analogues based upon the transition metal dichalcogenides TMDs; e.

However, the utility of these nanomaterials is limited by a few intrinsic shortcomings, such as a lack of a bandgap in graphene [ 4 ] and relatively low carrier mobility in MoS 2 [ 5 ]. Taken together, this has motivated the search for alternative 2D materials. Black phosphorus BP has sparked enormous research interest since its discovery in due to its distinctive structures and useful properties [ 6 ].

In the monolayer BP also known as phosphorene , each phosphorus atom is covalently bonded with three adjacent phosphorus atoms, thereby forming a bilayer structure along the zigzag direction and puckered structure along the armchair direction [ 7 ]. This structural anisotropy contributes to its exceptional properties, including its optical properties [ 8 ], mechanical properties [ 9 ], electrical conductivity [ 10 ], thermoelectric properties [ 11 ], and topological features [ 12 ], distinguishing it from other 2D materials [e.

Although numerous studies have been conducted to investigate the nano- and opto-electronic applications of BP, including its photonic applications based on its saturable absorption properties [ 13 , 14 ], little attention has been paid to its potential biomedical applications [ 15 , 16 ]. This might be mainly due to the lack of stability of black phosphorus when it is exposed to the aqueous environment or air. Several recent studies have demonstrated the feasibility of synthesizing novel BP nanostructures that are stable in water and air [ 17 - 20 ]. As one of the main components of nucleic acids, phosphorus is essential in maintaining human health, leading to a biocompatible material with extensive application potential in the biomedical field [ 23 , 24 ].

BP has been employed as a biosensing substance for the detection of target analytes e. It has also emerged as a potential agent for drug delivery and anti-tumour therapy owing to its high drug loading efficiency, good biocompatibility, and excellent photothermal and photodynamic properties [ 27 , 28 ]. Although BP-based biomedical application is still in its infancy with numerous technical challenges remaining to be solved, it may bring novel opportunities for future medical diagnosis and treatment. Therefore, extensive investigation on the potential of BP in biomedical applications, such as biosensing applications and regenerative medicine, would be highly desirable.

The sources of review articles on the fundamental properties of BP and its nano- and opto-electronic applications are extensive and readily available [ 29 - 32 ]. Recently, BP nanomedicine and sensing applications have been reviewed [ 33 , 34 ]. However, the unique fundamental properties of BP compared to other 2D materials and its advantages for diverse biomedical applications have not yet been clearly discussed. In light of the rising demand for BP as an alternative to graphene-based materials, there is a strong need for a timely and comprehensive review on a wide range of biomedical applications of BP, including colorimetric sensing, fluorescent sensing, electrochemical sensing, field effect transistor sensing, cancer imaging, cancer therapy and drug delivery Figure 1.

In this review article, the unique and fascinating characteristics of BP that contribute to its biomedical applications are first discussed and compared with the properties of other 2D materials e.

Lipid-based Films for Biomedical Applications [Video] - Advanced Science News

The different synthesis methods of BP are then summarized. The advantages of using BP and its biomedical applications in biosensing, bioimaging, drug delivery, and cancer therapy are subsequently reviewed. Finally, the existing challenges and future perspective of BP are briefly discussed. Black phosphorus BP as a promising material for biomedical applications. In particular, BP nanosheets and BP quantum dots BPQD have been widely used in biosensing, as field effect transistor sensors, colorimetric sensors, fluorescent sensors and electrochemical sensors, cancer imaging, drug delivery and cancer therapy.

Summary of the fundamental properties of BP compared to other 2D materials and its advantages for biomedical applications. Compared to other 2D materials, BP has been known as a more favorable material for biomedical applications due to its exceptional properties. A comparison of the unique properties of BP and other 2D materials is summarized in Table 1. Generally, graphene shows the highest carrier mobility, but it possesses zero-band gap and low ON-OFF current ratio, which may hinder its application in optical sensing, bio-imaging, and field effect transistor FET sensing [ 35 , 36 ].

However, their narrow range of band gap and low carrier mobility may hinder their applications in many fields e. The 2D hexagonal boron nitrite h-BN has been known to be a good proton conductor with high electrical resistance, adding its value to water electrolysis and fuel cells. However, its insulating properties limit its other applications e.

BP exhibits a direct and tunable band gap, which is dependent upon the number of layers i. BP can be easily exfoliated into monolayer or few-layer nanosheets due to the weak van der Waals forces among the stacked BP layers [ 40 ]. The wide tuning range of the BP band gap allows broad absorption across the visible light, infrared and ultraviolet regions [ 39 ], hence contributing to its excellent optical property compared to other 2D materials, which enables fluorescent and colorimetric detection of various types of bioanalytes e. This unique optical property also allows BP to be effectively used in biosensing, photoacoustic imaging, photodynamic therapy, photothermal therapy, and drug delivery [ 41 ].

BP also exhibits a high carrier mobility i. This may contribute to its high sensitivity to electrical perturbation, allowing it to detect gases based upon the electrical conductivity measurement [ 43 ]. Its ambipolar characteristic also enables it to detect both positively and negatively charged bioanalytes. The most attractive physical property of BP over other 2D materials is its high in-plane anisotropic properties.

For instance, the physical properties of BP e. These properties enable BP to be used for a variety of biosensing applications [ 25 ]. Generally, biocompatibility or toxicity of 2D materials is material-, size- and concentration-dependent [ 45 ].

Hence, it is essential to optimize the parameters of BP including, but not limited to, size and concentration before being used for biomedical applications. Overall, BP exhibits relatively low cytotoxicity or good biocompatibility; therefore, it is eligible for biomedical applications. Another distinct property of BP over other 2D materials is its natural in vivo biodegradability. BP is readily biodegradable inside the human body, producing nontoxic intermediates, such as phosphate, phosphite and other P x O y , upon exposure to water and oxygen; therefore, it is safe to be used for in vivo applications [ 22 ].

Recent studies have demonstrated that BP nanosheets, particularly those with a small size, have a relatively high reactivity with water and oxygen and are easily degradable in aqueous media [ 40 , 49 , 50 ].

Other 2D materials are not readily degradable and may accumulate inside the human body, which can cause cytotoxicity, and therefore require functionalization with other materials e. In short, BP exhibits a wide range of tunable bandgap, high carrier mobility, high ON-OFF current ratio, ambipolar characteristic, good biocompatibility, and in vivo biodegradability, indicating its greater potential in biomedical applications, including biosensing optical, FET and gas sensing , photoacoustic imaging, photodynamic and photothermal therapy, and drug delivery over other 2D materials.

This will be comprehensively discussed in Section 4. In fact, various fabrication methods of BP have been reviewed [ 53 ]. Top-down methods generally involve the exfoliation of bulk material into single or a few layered nanosheets through the application of driving force e.

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Therefore, compared to other 2D materials, thin layers of BP could be more easily produced by the aforementioned exfoliation methods. On the other hand, bottom-up methods involve the direct fabrication of nanomaterial from a specific precursor through chemical reactions e.