Peter Dunnill

Bio: Peter Dunnill is an academic researcher from University College London. The author has contributed to research in topics: Immobilized enzyme & Rhizopus nigricans. The author has an hindex of 50, co-authored 157 publications receiving 7336 citations.

A brief definition of regenerative medicine.

Abstract: While it could be said that regenerative medicine is what this journal publishes, that would be cyclical. It could also be claimed that most people interested in the field have a good grasp of what is entailed, and this is probably correct. But, as the field grows and there is a need to carry governments and public opinion along, it is probably worth having a simple explanation of regenerative medicine. And, it is simplicity that is the nub of the matter. There are already a lot of definitions [1–3] but all are lengthy and not the sort of thing scientists, start-ups or advocates can say succinctly when a pharma executive, government minister or member of the public asks for clarification. Here, we address this and the origins and relationships that help to define the field. One of the complications is that regenerative medicine has grown out of a good deal of prior activity. This includes surgery, surgical implants, such as artificial hips, and increasingly sophisticated biomaterial scaffolds. It also draws on hospital procedures such as bone marrow and organ transplants and it relates to tissue engineering. There is no absolute cut-off in the transformation of these into fully developed regenerative medicine but they each leave residues of their input that can mean the patient is not capable of being termed ‘of natural health’ with respect to the treated condition. Organ transplants often demand immune-suppressing drugs and metal hips can become loose with time, engineered tissue scaffolds can provoke inflammation and bone marrow sources are variable mixtures that also can be contaminated quite easily by the nature of the cell aspiration procedure. The central focus of regenerative medicine is human cells. These may be somatic, adult stem or embryo-derived cells and now there are versions

Imaging and photodynamic therapy: mechanisms, monitoring, and optimization.

Abstract: 1.1 Photodynamic Therapy and Imaging The purpose of this review is to present the current state of the role of imaging in photodynamic therapy (PDT). In order for the reader to fully appreciate the context of the discussions embodied in this article we begin with an overview of the PDT process, starting with a brief historical perspective followed by detailed discussions of specific applications of imaging in PDT. Each section starts with an overview of the specific topic and, where appropriate, ends with summary and future directions. The review closes with the authors’ perspective of the areas of future emphasis and promise. The basic premise of this review is that a combination of imaging and PDT will provide improved research and therapeutic strategies. PDT is a photochemistry-based approach that uses a light-activatable chemical, termed a photosensitizer (PS), and light of an appropriate wavelength, to impart cytotoxicity via the generation of reactive molecular species (Figure 1a). In clinical settings, the PS is typically administered intravenously or topically, followed by illumination using a light delivery system suitable for the anatomical site being treated (Figure 1b). The time delay, often referred to as drug-light interval, between PS administration and the start of illumination with currently used PSs varies from 5 minutes to 24 hours or more depending on the specific PS and the target disease. Strictly speaking, this should be referred to as the PS-light interval, as at the concentrations typically used the PS is not a drug, but the drug-light interval terminology seems to be used fairly frequently. Typically, the useful range of wavelengths for therapeutic activation of the PS is 600 to 800 nm, to avoid interference by endogenous chromophores within the body, and yet maintain the energetics necessary for the generation of cytotoxic species (as discussed below) such as singlet oxygen (1O2). However, it is important to note that photosensitizers can also serve as fluorescence imaging agents for which activation with light in the 400nm range is often used and has been extremely useful in diagnostic imaging applications as described extensively in Section 2 of this review. The obvious limitation of short wavelength excitation is the lack of tissue penetration so that the volumes that are probed under these conditions are relatively shallow. Open in a separate window Figure 1 (A) A schematic representation of PDT where PS is a photoactivatable multifunctional agent, which, upon light activation can serve as both an imaging agent and a therapeutic agent. (B) A schematic representation of the sequence of administration, localization and light activation of the PS for PDT or fluorescence imaging. Typically the PS is delivered systemically and allowed to circulate for an appropriate time interval (the “drug-light interval”), during which the PS accumulates preferentially in the target lesion(s) prior to light activation. In the idealized depiction here the PS is accumulation is shown to be entirely in the target tissue, however, even if this is not the case, light delivery confers a second layer of selectivity so that the cytotoxic effect will be generated only in regions where both drug and light are present. Upon localization of the PS, light activation will result in fluorescence emission which can be implemented for imaging applications, as well as generation cytotoxic species for therapy. In the former case light activation is achieved with a low fluence rate to generate fluorescence emission with little or no cytotoxic effect, while in the latter case a high fluence rate is used to generate a sufficient concentration of cytotoxic species to achieve biological effects.

Biosynthesis of nanoparticles: technological concepts and future applications

Abstract: Nanotechnology involves the production, manipulation and use of materials ranging in size from less than a micron to that of individual atoms. Although nanomaterials may be synthesized using chemical approaches, it is now possible to include the use of biological materials. In this review, we critically assess the role of microorganisms and plants in the synthesis of nanoparticles.