Technology

PSCN Technology Focus

The creation of Photodynamic Super Conjugated Nanoparticles (PSCN) consisting of selective bacteriophage carriers and novel ultra-sensitive near-infrared photodynamic therapy molecular conjugates provide an opportunity for:

• Selectively attaching to targeted cells, pathogens, and other materials
• Selectively killing almost any cell or pathogen type using a combination of singlet oxygen and super oxide anions, with minimal anticipated damage to non-targeted cells even one cell width away from the targets

The techniques being explored should be effective on tumors or localized infections, but should also be able to capture and destroy isolated free cancer cells or pathogens anywhere the patient’s tissue is exposed to the activating light, with greatly reduced risk of damage to neighboring cells or other organs.

Activity is restricted to where the light is provided, providing both zoned and individual cell selectivity

• Near-infrared light from LEDs or other light sources in the 750nm-850nm spectral range provides the energy for activating these unique photodynamic therapy (PDT) conjugates.

This near-infrared wavelength range occurs naturally in sunlight and in most man made light sources. This light spectrum permits the deepest tissue penetration of any non-ionizing radiation and can even penetrate bone, but does not damage tissue at moderately high intensities.

Several times higher incident intensity light can be used in this spectral range without heat discomfort than is practical for light in the visible light range. Because the body’s tissue is highly transmissive to these wavelengths, energy is distributed over a much greater volume of tissue than in conventional (below 700nm range) photodynamic therapy (PDT). Higher intensity coupled with higher transmission provides depth of potential effectiveness from the light source.

When activating light in this near-infrared spectrum is paired with 1) high selectivity drug carriers that concentrate the drugs on the targeted cells, 2) PDT materials exhibiting very high extinction coefficients to efficiently absorb light, and 3) high quantum efficiencies at producing ROS to chemically act on the targeted materials, minimally-invasive and non-invasive surgical techniques should become viable for treating cancers and pathogens deep in the body that today pose high tissue damage risk and patient survival risk.

Treatments of pathogens could potentially be very fast (under 2 hours treatment time instead of days after the selective targeting carriers are produced), minimizing the tissue damage aggressive infections can cause, in addition to providing a potential opportunity for treating difficult to treat pathogen infections.

Illustration 1: Conceptual drawing of PSCN

In this conceptual diagram we show a bacteriophage with photodynamic compound conjugates and fluorescent reporters attached to the phages coat. Most of the binding sites on the phage are not used by the attached compounds, leaving these sites available to provide affinity binding to the targeted cells or pathogens.

Filamentous bacteriophages (phage) can act as carriers for photodynamic materials. Human-tumor-specific or target pathogen-specific peptides genetically fused to the approximately 4000 copies of the filamentous phages’ major pVIII coat proteins can be selected from multi-billion phage clone libraries by their ability to bind to specific cancer cells or pathogen surfaces.

When billions of phage variants are applied to cancer cells obtained from a biopsy or to samples of a pathogen, those few phage with an affinity to the target cells or pathogens are retained. The other phages are then rinsed away. The retained phages are feed bacteria and rapidly increase in quantity. This selection process is repeated several times until many phage with a high affinity to the target cell types remain. A variation of this process can be used to verify the selected phage have low affinity to normal cells.

Hundreds of photoreactive conjugates and fluorescent “reporting tags” can practically be bonded to, and carried on each phage. Also, many thousands carrier phages can attach to each target cell.

More About Bacteriophages (Phages)

Phages are almost always present in the human intestinal tract, feeding on bacteria.

Over a hundred strains of phages are typically present in an average person’s intestines, and to a lesser degree are prsent in other parts of the body. Phages frequently go unnoticed since they minimally interact with human or animal cells. While the selected phage being researched for this treatment do attach to cell membranes, the phage themselves are not expected to directly interfere with even the targeted cells. Phage can feed on some bacterial pathogens, but the proposed therapy does not rely on lytic interactions between bacteria and phage.

Filamentous phages have been shown to pass through almost all of the body’s multi-cellular boundaries and most biofilms, but they do not penetrate individual human cell membranes. While phages are continually entering the body through the intestines, they are quickly removed in a similar manner as particles from the blood stream by the liver so their concentration is typically low in the blood. Phages are therefore typically only present in small quantities in various tissues including blood, lymph system, and brain.

Conceptual Sequence of Events in Future PSCN Therapy

	Cancer cell or pathogen next to normal cells before treatment.
Illustration 2: Cancer cell or pathogen next to normal cells before treatment

PSCN are introduced to the body. PSCN can be introduced by IV or injection. PSCN could also potentially be topically introduced or absorbed through the digestive system, depending on the situation and treatment or diagnostic objective. The PSCN flow past most of the cells in the body and do not attach, but the phage carriers with matched binding sites adhere with high affinity to the surface of the targeted cancer cells or pathogens. After as little as 30 minutes, the body should remove almost all of the unattached phage, leaving phage covering the targeted cells, but minimally or not attached to non-targeted cells.

Illustration 3: PSCN are introduced to the body.

 

Activating light for the fluorescent reporters and/or the photodynamic reactive materials in the PSCN is applied to the skin surface or by light probe in the vicinity of the area to the treated. Accurate placement of probes should be less important for most treatments than required for conventional photodynamic therapy. The selected light penetrates though controlled depths of tissue, depending on the intensity and wavelengths used. Near-infra red light can penetrate long distances, providing light energy through large volumes of tissue. PSCN therapy could potentially be effective through over 3 inches inches of tissue, depending on the tissue type and other parameters. PSCN efficiently absorb this light. PSCN with or without added fluorescent reporters can absorb the externally supplied light and then emit their own unique color or spectrum light. This emitted light or thermally induced sonic pulses and be detected, letting the physician (local or remote via telecommunications) know if the expected localized concentration of PSCN has occurred. PSCN should be able to uniquely tell the physician if it is likely to work properly before light activation and how effective the treatment has been after light activation of the PSCN.

Illustration 4: Activating light for the fluorescent reporters and/or the photodynamic reactive materials in the PSCN is applied to the skin surface or by light probe in the vicinity of the area to the treated. PSCN efficiently absorb this light. PSCN with or without added fluorescent reporters can absorb the externally supplied light and then emit their own unique color or spectrum light letting the physician know if the expected localized concentration of PSCN has occurred.

During additional activating light exposure of the PSCN, the PSCN “continuously manufacturers” reactive oxygen species (ROS) such as singlet oxygen and super oxide anion from the interstitial oxygen present in the body. This drug manufacturing on the target cells occurs until the light is turned off or the PSCN stops producing ROS. Stopping ROS generation after a desired ROS dose is obtained regardless of light intensity or duration of exposure is an expected advantage of planned PSCN technology. The ROS is the active chemical that damages the target cells, not the PSCN itself.

Illustration 5: During additional activating light exposure of the PSCN, the PSCN “continuously manufacturers” reactive oxygen species (ROS) such as singlet oxygen and super oxide anion from the interstitial oxygen present in the body. This drug manufacturing on the target cells occurs until the light is turned off or the PSCN stops producing ROS.

After treatment, the targeted cancer cells or pathogens should quickly stop dividing and then die over a few hours to a few days time. These dead cells or dead pathogens should be reabsorbed by the body or excreted. Seriously damaged cancer cells with phage attached would also be targets for attack by the body’s immune system, providing a secondary treatment benefit. Even surviving pathogens from low dose treatments would also likely be less able to reproduce, and may have their ability to produce toxins reduced. The PSCN can continue to be monitored as was done in Illustration 4, with or with out the photodynamic compounds present. Success of the treatment can be determined by verifying the PSCN signal is dissipating. Low dose fluorescent-tag-only or normal PSCN can be used to re-decorate and reveal if the previously targeted type of cancer cells or the select pathogens remain or recover.

Illustration 6: After treatment, the targeted cancer cells or pathogens should quickly stop dividing and then die over a few hours to a few days time. These dead cells or dead pathogens should be reabsorbed by the body or excreted.

 

A unique hoped-for characteristic of the PSCN approach is that it could potentially target multiple mutations of cancer cells if the biopsy contains samples of the multiple cancer cell types. Also, early metastasizing cancer may be more effectively treated using PSCN since large volume of tissue could be treated with minimal damage to healthy cells.

The PSCN’s non-reactivity except where light is present should allow the liver and other organs to potentially accumulate and/or excrete the PSCN without damage or dangerous side effects. There will likely be risks of immune responses to PSCN and the byproducts of treated cancer cells or pathogens, and other effects that need to be carefully studied.

Unlike many other photodynamic therapies, most planned variations of PSCN are not expected to enter cells through the cell membranes. Only the outer membranes of the targeted cells should be damaged by the ROS. We need to experimentally test that many types of non-targeted cells that have only a small number of PSCN attached would be unlikely to be irreparably damaged, and that cells away from the activation light exposure zone will be relatively unaffected.

Because PSCN is only chemically active for short periods of time during the light exposure and are expected to be quickly eliminated from the body, long term pathogen resistance should be more difficult to develop than with conventional chemotherapy drugs and antibiotics. Also, most new resistant pathogen strains that may be created or discovered should be quickly able to be treated by a new selective PSCN phage variant. This ability to quickly generate new targeted variations of the drug can kill a great many bacteria or and probably any cancer cell type it can be selectively targeted to offers exciting potential for future new treatment methodology.

Novel Materials In Development

Multiple materials are under development and being characterized, but unique new materials already show significant promise for:

• Highly engineered photodynamic (PDT) materials with high sensitivity and reactivity to proteins that can enable anti-cancer or antibiotic activation several inches through tissue with minimal visual light spectrum sensitivity
• Phage carrier technology for photodynamic treatment of cancer, pathogens, and other targeted materials. Also, near-infrared absorbing reporter capabilities with multiple feedback mechanisms
• Optoelectronic light sources and sensor matrices to activate and provide feedback from novel targeting PDT nanoparticles. These PSCN activation and analysis patch systems could be highly portable and potentially low cost if produced in large quantities.