On skin substitutes for wound healing: Current products, limitations, and future perspectives

Cutaneous wound healing is a highly coordinated process involving numerous molecular pathways that regulate the function of specific skin cell types. One of the key decisions in acute and/or chronic wound healing management is to choose the skin substitute that, based on its composition and/or properties, may act as permanent skin replacement or temporary wound cover. The current products however are limited in their action, especially in the context of large chronic wounds or extensive second-/third-degree burns, due to the risk of developing infection, the limited vascularization, the inability to integrate to host tissue, and the lack in the healed area of skin apparatus responsible for temperature control, pigmentation, immune regulation, and nerve supply. In addition, the high cost of skin substitutes precludes their use in small- and moderate-size burns because they are economically impractical and protract the time to definitive wound closure. Thus, the need to develop cost-effective substitutes of high quality is imperative. The purpose of this review is to discuss current available products, their limitations and to provide some perspectives on future research toward generation of cost-effective, high-quality substitutes.

Twenty-four hour ex-vivo normothermic machine perfusion in rat livers

Ex-vivo liver perfusion (EVLP) is an ideal platform to study liver disease, therapeutic interventions, and pharmacokinetic properties of drugs without any patient risk. Rat livers are an ideal model for EVLP due to less organ quality variability, ease of hepatectomy, well-defined molecular pathways, and relatively low costs compared to large animal or human perfusions. However, the major limitation with rat liver normothermic machine perfusion (NMP) is maintaining physiologic liver function on an ex-vivo machine perfusion system. To address this need, our research demonstrates 24-hour EVLP in rats under normothermic conditions. Early (6 hour) perfusate transaminase levels and oxygen consumption of the liver graft are shown to be good markers of perfusion success and correlate with viable 24-hour post-perfusion histology. Finally, we address overcoming challenges in long-term rat liver perfusions such as rising intrahepatic pressures and contamination, and offer future directions necessary to build upon our work.

Current methods of electroporation for efficient vaccination uptake

With the resurgence of illnesses, such as measles, it is of utmost importance that a high percentage of the local and global population be vaccinated. Diseases, such as measles, HepB, Hib, and others, are suppressed when 93%–95% of a population has been vaccinated against them, generating herd immunity. Lack of vaccination can lead to lifelong consequences. Barriers to vaccination include costs, lack of healthcare worker knowledge, reliance on cold chain storage, age, and personal beliefs. Vaccinations are usually administered as subcutaneous or intramuscular injections, though some oral vaccines exist. The use of intradermal or intramuscular electroporation (ID-EP and IM-EP) as an adjuvant has demonstrated benefits over traditional vaccination methods, while also having some issues, which require careful consideration. Issues for consideration include a lack of standardized equipment and pulsing protocols while benefits include dose sparing, long-term immunogenicity, and higher titer levels after a single dose compared to the gold standard. ID-EP has been shown to have better transfection rates over IM-EP, while IM-EP has demonstrated faster seroconversion rates (SRs) over IM injection alone. Improvements such as standardizing equipment with larger injection volumes, multiple EP site locations and/or disposable, predosed, lyophilized vaccine cartridges could contribute to more rapid deployment of vaccines without relying on cold chain storage and trained healthcare workers, at a reduced cost while still providing adequate levels of immunity against disease.

Asymmetric voltage multiplying circuit coupled to sliding electrodes for biomass fractionation with high-voltage and high current pulsed electric fields

Pulsed electric field (PEF) is an emerging technology for biomass processing and fractionation by electroporation of cell membrane. Nevertheless, PEF technology and devices require tailoring and adaptation for each specific type of biomass. Such an optimization requires convenient and adaptable laboratory systems, which will enable both electrical and mechanical parameters determination before process upscaling. In this work, we report on the design and development of a laboratory PEF system that allows applying for up to 4 kV, 1 kA pulses with 1–100 [Formula: see text]s and total power dissipation of 20 W and up to 25 kg of mechanical load. The design of an asymmetric voltage multiplying circuit allows for controlling pulse parameters for each pulse in series. Such an approach enables precise adaptation of PEF to the changing conductivity of the biomass, minimizing the total invested energy in the process. The system was tested on highly conductive marine macroalgae Ulva sp, a promising but challenging feedstock for the biorefinery. This work provides a design of an adaptable PEF device, important for biomass processing with electroporation.

Multi-layer stackable tissue culture platform for 3D co-culture

In vitro tools, which can enable development of models that replicate the cell microenvironment associated with complex diseases such as osteoarthritis (OA), are critically needed. In OA, catabolic and inflammatory processes orchestrated by multiple cell types lead to the eventual destruction of articular cartilage. To address this need, our group developed a device that will enable investigation of complex cell systems. Our stackable tissue culture insert was fabricated and characterized with respect to biocompatibility, ease of use, and potential for tissue culture applications. The stackable tissue culture inserts can be easily modified, fabricated, and assembled into commercially available multi-well plates. In vitro studies conducted with three different cell types demonstrated high cell viability and functional secretion when cultured in the stackable inserts. Furthermore, synergistic effects when the three cell types were cultured together were observed. This demonstrates the need to more fully interrogate in vitro culture systems, and this stackable insert can provide a tool to fill the current technological void to do so.

First-in-human evaluation of a hand-held automated venipuncture device for rapid venous blood draws

Obtaining venous access for blood sampling or intravenous (IV) fluid delivery is an essential first step in patient care. However, success rates rely heavily on clinician experience and patient physiology. Difficulties in obtaining venous access result in missed sticks and injury to patients, and typically require alternative access pathways and additional personnel that lengthen procedure times, thereby creating unnecessary costs to healthcare facilities. Here, we present the first-in-human assessment of an automated robotic venipuncture device designed to safely perform blood draws on peripheral forearm veins. The device combines ultrasound imaging and miniaturized robotics to identify suitable vessels for cannulation and robotically guide an attached needle toward the lumen center. The device demonstrated results comparable to or exceeding that of clinical standards, with a success rate of 87% on all participants ([Formula: see text]), a 97% success rate on nondifficult venous access participants ([Formula: see text]), and an average procedure time of [Formula: see text][Formula: see text]s ([Formula: see text]). In the future, this device can be extended to other areas of vascular access such as IV catheterization, central venous access, dialysis, and arterial line placement.

Macrophage modulation by polymerized hemoglobins: Potential as a wound-healing therapy

Chronic skin wounds are hypoxic and are stalled in a pro-inflammatory state. Hemoglobin (Hb)-based oxygen carriers have shown potential in increasing oxygen delivery to aid wound healing. Macrophages also take up Hb, thus altering their phenotype and the regulation of inflammation. Herein, we compared the effect of Hb and polymerized Hbs (PolyHbs) on the phenotype of human macrophages. Macrophages were incubated with Hb or different forms of PolyHbs, and the inflammatory secretion profile was analyzed. PolyHbs were produced by polymerizing Hb in the relaxed (R) or tense (T) quaternary state and by varying the molar ratio of the glutaraldehyde crosslinking agent to Hb. Hb decreased the secretion of most measured factors. PolyHb treatment led to generally similar secretion profiles; however, Hb had more similar trends to R-state PolyHb. Ingenuity pathway analysis predicted positive outcomes in wound healing and angiogenesis for T-state PolyHb prepared with a 30:1 (glutaraldehyde:Hb) polymerization ratio. When tested in diabetic mouse wounds, T-state PolyHb resulted in the greatest epidermal thickness and vascular endothelial CD31 staining. Thus, the effects of PolyHb on macrophages are affected by the polymerization ratio and the quaternary state, and T-state PolyHb yields secretion profiles that are most beneficial in wound healing.

Emerging micro and nanotechnologies in neuroscience: Devices, fabrication methods, and implementation in monitoring of neural activity and drug delivery

Neural activity that occur during motor movement, speech, thought, and various other events can be observed in the form of brainwaves composed of synchronized electrical pulses emitted from adjoining communicative neurons. Observations of these brainwaves have been made possible through neurodevices, which can detect changes in electrical and/or mechanical parameters. For decades, the field of neuroscience has been enriched by the utilization of neurotechnologies at the microscale, which has begun to gain further enhancement with the introduction of nanotechnology. For example, microelectrodes were initially used for only extracellular measurements, but over the past decade, developments have been made to also record intracellular signals. Likewise, nanoknives, which gained popularity due to their versatility, can now be used for both fabricating bio-Micro-Electro-Mechanical Systems (MEMS) and also as a neurosurgery tool. Thus, considerable efforts have been made over the years to make micro- and nanosystems reliable, accurate, and sensitive to neural activity. In the late 20th century, several sophisticated technologies, including magnetic resonance imaging (MRI), computed tomography (CT), and intracranial pressure (ICP) monitoring have been integrated with MEMS. Furthermore, existing biotechnologies are being miniaturized at both the system and component level. For example, there is a remarkable interest in the field of neuroscience to utilize microfluidic technology as a diagnostic tool using specimens such as cerebrospinal fluid (CSF). Microfluidic devices are also employed as biocompatible drug delivery systems to target cells, tissues, and organs. This paper summarizes the recent developments in micro- and nano-scale neurotechnologies, including devices, fabrication processes, detection methods, their implementation challenges, in neural stimulation, monitoring, and drug delivery. This review discusses recent developments in micro and nanotechnologies, fabrication methods, and their implementation in neuroimaging, neurostimulation, monitoring of neural activities, and neural drug delivery.

A protein interaction free energy model based on amino acid residue contributions: Assessment of point mutation stability of T4 lysozyme

Here we present a model to estimate the interaction free energy contribution of each amino acid residue of a given protein. Protein interaction energy is described in terms of per-residue interaction factors, [Formula: see text]. Multibody interactions are implicitly captured in [Formula: see text] through the combination of amino acid terms ([Formula: see text]) guided by local conformation indices ([Formula: see text]). The model enables construction of an interaction factor heat map for a protein in a given fold, allows prima facie assessment of the degree of residue–residue interaction, and facilitates a qualitative and quantitative evaluation of protein association properties. The model was used to compute thermal stability of T4 bacteriophage lysozyme mutants across seven sites. Qualitative assessment of mutational effects provides a straightforward rationale regarding whether a particular site primarily perturbs native or non-native states, or both. The presented model was found to be in good agreement with experimental mutational data ([Formula: see text]) and suggests an approach by which to convert structure space into energy space.

Application of pulsed electric fields for the valorization of platelets with no therapeutic value for transfusion medicine

Platelets are blood components with high biomedical potential due to their physiological role in wound healing and their rich growth factor content. This paper describes proof-of-concept experiments aimed to produce a new blood-derived product by applying pulsed electric fields (PEF) to platelet concentrates (PC) with no therapeutic value for transfusion medicine. A human platelet concentrate suspension was subjected to a PEF treatment of 1 pulse, 5[Formula: see text]kV/cm, for 2[Formula: see text][Formula: see text]s. Release of platelet-derived growth factor (PDGF) from the electroporated platelets was measured by ELISA. Furthermore, the biological activity of the obtained blood-derived product was characterized. Human mesenchymal stem cells (hMSC) were cultured in the presence of the proteins released from the platelets after PEF application and evaluated for their expansion potential. Results show that platelet concentrates subjected to a single PEF treatment can release PDGF to the supernatant. Protein release from the single and transient PEF cycle was confirmed by the expansion of hMSC cultured with a medium supplemented with the platelet releasate obtained from electroporated platelets. These results demonstrate the potential of a new application of PEF for the valorization of PC into a biomedical product with therapeutic value.